U.S. patent application number 16/438281 was filed with the patent office on 2019-09-26 for electronic ophthalmic lens with sleep monitoring.
The applicant listed for this patent is Johnson & Johnson Vision Care, Inc.. Invention is credited to Frederick A. Flitsch, Randall B. Pugh, Adam Toner.
Application Number | 20190290192 16/438281 |
Document ID | / |
Family ID | 57240852 |
Filed Date | 2019-09-26 |
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United States Patent
Application |
20190290192 |
Kind Code |
A1 |
Pugh; Randall B. ; et
al. |
September 26, 2019 |
ELECTRONIC OPHTHALMIC LENS WITH SLEEP MONITORING
Abstract
An eyelid position sensor system and/or an eye movement sensor
system for an ophthalmic lens having an electronic system is
described herein for recording data associated with sleep of the
wearer. The eyelid position sensor system is part of an electronic
system incorporated into the ophthalmic lens. The electronic system
in at least one embodiment includes a system controller and a data
manager. In at least one embodiment, the eyelid position sensor
system is utilized to determine eyelid position and the eye
movement sensor system is utilized to determine eye position for
the system controller to determine if the wearer is awake, asleep,
or in REM sleep.
Inventors: |
Pugh; Randall B.; (St.
Johns, FL) ; Flitsch; Frederick A.; (New Windsor,
NY) ; Toner; Adam; (Jacksonville, FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Johnson & Johnson Vision Care, Inc. |
Jacksonville |
FL |
US |
|
|
Family ID: |
57240852 |
Appl. No.: |
16/438281 |
Filed: |
June 11, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14924065 |
Oct 27, 2015 |
10314530 |
|
|
16438281 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/1103 20130101;
G02C 7/04 20130101; A61B 5/18 20130101; A61B 5/4812 20130101; A61B
2560/0209 20130101; A61B 5/002 20130101; A61B 5/6821 20130101; A61B
3/113 20130101; A61B 5/4809 20130101; G02C 11/10 20130101; G01J
1/42 20130101 |
International
Class: |
A61B 5/00 20060101
A61B005/00; A61B 5/18 20060101 A61B005/18; G02C 7/04 20060101
G02C007/04; A61B 5/11 20060101 A61B005/11; G02C 11/00 20060101
G02C011/00; G01J 1/42 20060101 G01J001/42 |
Claims
1. A powered ophthalmic lens, the powered ophthalmic lens
comprising: a contact lens; an eyelid position sensor system in the
contact lens, the eyelid position sensor system including a sensor
array having a plurality of measurement points vertically spaced
from each other to detect eyelid position and a signal conditioner
configured to sample the measurement points in the sensor array to
detect eyelid position and provide an output lid signal; an eye
movement sensor system in the contact lens, the eye movement sensor
system including at least one sensor to track and determine eye
position and a signal conditioner cooperatively associated with the
sensor and configured to track and determine eye position in
spatial coordinates based on information from the sensor output and
provide an output movement signal; a system controller electrically
connected with said eyelid position sensor system and said eye
movement sensor system, said system controller configured to sample
said eyelid position sensor system and said eye movement system
based on at least one predetermined sampling rate; and a memory in
electrical communication with said system controller, and wherein
said system controller stores data based on each sample in said
memory.
2. The powered ophthalmic lens according to claim 1, further
comprising an accumulator; and wherein said system controller is
configured to store a corresponding reading from said accumulator
for each sample data set stored.
3. The powered ophthalmic lens according to claim 2, further
comprising: a power source electrically connected to said lid
position sensor system, said eye movement sensor system, and said
system controller; and a resource management system in electrical
communication with at least one of said power source and said
memory; said resource management system configured to determine at
least one of a low energy level and memory storage threshold
exceeded and in response to a positive determination, said resource
management system is configured to at least one of reduce all
sampling rates of the system, terminate all sampling of said eyelid
position sensor system and said eye movement system, and replace
earlier data with newer data when memory storage threshold is
exceeded.
4. A system comprising: the powered ophthalmic lens according to
claim 2; and a base station capable of housing said lens, said base
station including a housing having a cavity of sufficient size for
at least one lens, a clock, a communication system configured to
communicate with any lens inserted in said housing including
activating said lens and downloading data stored in said memory in
said lens; a memory configured to store downloaded data; and means
for communicating with an external computer to transmit data
received from said memory in said lens.
5. The powered ophthalmic lens according to claim 1, further
comprising a communications system configured to communicate with
an external device.
6. The powered ophthalmic lens according to claim 5, wherein said
system controller transmits any received signal output to the
external device through said communications system.
7. The powered ophthalmic lens according to claim 1, wherein said
eye movement system includes at least one accelerometer.
8. The powered ophthalmic lens according to claim 7, wherein said
eye movement sensor system signal conditioner provides an output
when a signal from said at least one accelerometer exceeds a
movement threshold.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This patent application is a Divisional of U.S. patent
application Ser. No. 14/924,065 filed Oct. 27, 2015, and entitled
"ELECTRONIC OPHTHALMIC LENS WITH SLEEP MONITORING."
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to a powered or electronic
ophthalmic lens, and more particularly, to a powered or electronic
ophthalmic lens having a sensor and associated hardware and
software for detecting sleep.
Discussion of the Related Art
[0003] As electronic devices continue to be miniaturized, it is
becoming increasingly more likely to create wearable or embeddable
microelectronic devices for a variety of uses. Such uses may
include monitoring aspects of body chemistry, administering
controlled dosages of medications or therapeutic agents via various
mechanisms, including automatically, in response to measurements,
or in response to external control signals, and augmenting the
performance of organs or tissues. Examples of such devices include
glucose infusion pumps, pacemakers, defibrillators, ventricular
assist devices and neurostimulators. A new, particularly useful
field of application is in ophthalmic wearable lenses and contact
lenses. For example, a wearable lens may incorporate a lens
assembly having an electronically adjustable focus to augment or
enhance performance of the eye. In another example, either with or
without adjustable focus, a wearable contact lens may incorporate
electronic sensors to detect concentrations of particular chemicals
in the precorneal (tear) film. The use of embedded electronics in a
lens assembly introduces a potential requirement for communication
with the electronics, for a method of powering and/or re-energizing
the electronics, for interconnecting the electronics, for internal
and external sensing and/or monitoring, and for control of the
electronics and the overall function of the lens.
[0004] The human eye has the ability to discern millions of colors,
adjust easily to shifting light conditions, and transmit signals or
information to the brain at a rate exceeding that of a high-speed
internet connection. Lenses, such as contact lenses and intraocular
lenses, currently are utilized to correct vision defects such as
myopia (nearsightedness), hyperopia (farsightedness), presbyopia
and astigmatism. However, properly designed lenses incorporating
additional components may be utilized to enhance vision as well as
to correct vision defects.
[0005] Contact lenses may be utilized to correct myopia, hyperopia,
astigmatism as well as other visual acuity defects. Contact lenses
may also be utilized to enhance the natural appearance of the
wearer's eyes. Contact lenses or "contacts" are simply lenses
placed on the anterior surface of the eye. Contact lenses are
considered medical devices and may be worn to correct vision and/or
for cosmetic or other therapeutic reasons. Contact lenses have been
utilized commercially to improve vision since the 1950s. Early
contact lenses were made or fabricated from hard materials, were
relatively expensive and fragile. In addition, these early contact
lenses were fabricated from materials that did not allow sufficient
oxygen transmission through the contact lens to the conjunctiva and
cornea which potentially could cause a number of adverse clinical
effects. Although these contact lenses are still utilized, they are
not suitable for all patients due to their poor initial comfort.
Later developments in the field gave rise to soft contact lenses,
based upon hydrogels, which are extremely popular and widely
utilized today. Specifically, silicone hydrogel contact lenses that
are available today combine the benefit of silicone, which has
extremely high oxygen permeability, with the proven comfort and
clinical performance of hydrogels. Essentially, these silicone
hydrogel based contact lenses have higher oxygen permeability and
are generally more comfortable to wear than the contact lenses made
of the earlier hard materials.
[0006] Conventional contact lenses are polymeric structures with
specific shapes to correct various vision problems as briefly set
forth above. To achieve enhanced functionality, various circuits
and components have to be integrated into these polymeric
structures. For example, control circuits, microprocessors,
communication devices, power supplies, sensors, actuators,
light-emitting diodes, and miniature antennas may be integrated
into contact lenses via custom-built optoelectronic components to
not only correct vision, but to enhance vision as well as provide
additional functionality as is explained herein. Electronic and/or
powered ophthalmic lenses may be designed to provide enhanced
vision via zoom-in and zoom-out capabilities, or just simply
modifying the refractive capabilities of the lenses. Electronic
and/or powered contact lenses may be designed to enhance color and
resolution, to display textual information, to translate speech
into captions in real time, to offer visual cues from a navigation
system, and to provide image processing and internet access. The
lenses may be designed to allow the wearer to see in low-light
conditions. The properly designed electronics and/or arrangement of
electronics on lenses may allow for projecting an image onto the
retina, for example, without a variable-focus optic lens, and
provide novelty image displays. Alternately, or in addition to any
of these functions or similar functions, the contact lenses may
incorporate components for the noninvasive monitoring of the
wearer's biomarkers and health indicators. For example, sensors
built into the lenses may allow a diabetic patient to keep tabs on
blood sugar levels by analyzing components of the tear film without
the need for drawing blood. In addition, an appropriately
configured lens may incorporate sensors for monitoring cholesterol,
sodium, and potassium levels, as well as other biological markers.
This, coupled with a wireless data transmitter, could allow a
physician to have almost immediate access to a patient's blood
chemistry without the need for the patient to waste time getting to
a laboratory and having blood drawn. In addition, sensors built
into the lenses may be utilized to detect light incident on the eye
to compensate for ambient light conditions or for use in
determining blink patterns.
[0007] The proper combination of devices could yield potentially
unlimited functionality; however, there are a number of
difficulties associated with the incorporation of extra components
on a piece of optical-grade polymer. In general, it is difficult to
manufacture such components directly on the lens for a number of
reasons, as well as mounting and interconnecting planar devices on
a non-planar surface. It is also difficult to manufacture to scale.
The components to be placed on or in the lens need to be
miniaturized and integrated onto just 1.5 square centimeters of a
transparent polymer while protecting the components from the liquid
environment on the eye. It is also difficult to make a contact lens
comfortable and safe for the wearer with the added thickness of
additional components.
[0008] Given the area and volume constraints of an ophthalmic
device such as a contact lens, and the environment in which it is
to be utilized, the physical realization of the device must
overcome a number of problems, including mounting and
interconnecting a number of electronic components on a non-planar
surface, the bulk of which comprises optical grade plastic.
Accordingly, there exists a need for providing a mechanically and
electrically robust electronic contact lens.
[0009] As these are powered lenses, energy or more particularly
current consumption, to run the electronics is a concern given
battery technology on the scale for an ophthalmic lens. In addition
to normal current consumption, powered devices or systems of this
nature generally require standby current reserves, precise voltage
control and switching capabilities to ensure operation over a
potentially wide range of operating parameters, and burst
consumption, for example, up to eighteen (18) hours on a single
charge, after potentially remaining idle for years. Accordingly,
there exists a need for a system that is optimized for low-cost,
long-term reliable service, safety and size while providing the
required power.
[0010] In addition, because of the complexity of the functionality
associated with a powered lens and the high level of interaction
between all of the components comprising a powered lens, there is a
need to coordinate and control the overall operation of the
electronics and optics comprising a powered ophthalmic lens.
Accordingly, there is a need for a system to control the operation
of all of the other components that is safe, low-cost, and
reliable, has a low rate of power consumption and is scalable for
incorporation into an ophthalmic lens.
[0011] Powered or electronic ophthalmic lenses may have to account
for certain unique physiological functions from the individual
utilizing the powered or electronic ophthalmic lens. More
specifically, powered lenses may have to account for blinking,
including the number of blinks in a given time period, the duration
of a blink, the time between blinks and any number of possible
blink patterns, for example, if the individual is dosing off. Blink
detection may also be utilized to provide certain functionality,
for example, blinking may be utilized as a means to control one or
more aspects of a powered ophthalmic lens. Additionally, external
factors, such as changes in light intensity levels, and the amount
of visible light that a person's eyelid blocks out, have to be
accounted for when determining blinks. For example, if a room has
an illumination level between fifty-four (54) and one hundred
sixty-one (161) lux, a photosensor should be sensitive enough to
detect light intensity changes that occur when a person blinks.
[0012] Ambient light sensors or photosensors are utilized in many
systems and products, for example, on televisions to adjust
brightness according to the room light, on lights to switch on at
dusk, and on phones to adjust the screen brightness. However, these
currently utilized sensor systems are not small enough and/or do
not have low enough power consumption for incorporation into
contact lenses.
[0013] It is also important to note that different types of blink
detectors may be implemented with computer vision systems directed
at one's eye(s), for example, a camera digitized to a computer.
Software running on the computer can recognize visual patterns such
as the eye open and closed. These systems may be utilized in
ophthalmic clinical settings for diagnostic purposes and studies.
Unlike the above described detectors and systems, these systems are
intended for off-eye use and to look at rather than look away from
the eye. Although these systems are not small enough to be
incorporated into contact lenses, the software utilized may be
similar to the software that would work in conjunction with powered
contact lenses. Either system may incorporate software
implementations of artificial neural networks that learn from input
and adjust their output accordingly. Alternately, non-biology based
software implementations incorporating statistics, other adaptive
algorithms, and/or signal processing may be utilized to create
smart systems.
[0014] There are a variety of jobs that require the worker to be
aware and awake, for example, a truck driver, a security guard and
military personnel on duty. It would be counterproductive and lead
to potential issues if the worker were to fall asleep while
performing their duties. Many of these jobs are such that the
worker is required to have mobility while performing their duties
and as such a fixed base monitoring system is not practical for
providing monitoring of these workers. Furthermore, there are many
jobs requiring regulated amounts of sleep in off-hours, which are
manually logged by the worker instead of having automatic logging
of the worker's sleep to provide better records.
[0015] Accordingly, there exists a need for a means and method for
detecting certain physiological functions, such as a length of eye
closure or a blink. The sensor being utilized needs to be sized and
configured for use in a contact lens. In addition there exists a
need to detect the position of a user's eyelids. An eyelid position
sensor could be used to detect that a user is falling asleep, for
example, to log a data event of the wearer falling asleep. There
are existing systems for detecting lid position; however, they are
limited to devices like camera imagers, image recognition, and
infrared emitter/detector pairs which rely on reflection off the
eye and eyelid. Existing systems to detect lid position also rely
on the use of spectacles or clinical environments and are not
easily contained within a contact lens.
SUMMARY OF THE INVENTION
[0016] In at least one embodiment, a method for monitoring sleep
with a powered ophthalmic lens, the method includes: activating the
powered ophthalmic lens; initiating an accumulator on the lens to
track a passage of time; determining at a first lid sampling rate
whether lid closure has occurred; when lid closure is detected,
sampling at least once at least one of an accelerometer and a
transducer, and determining whether a threshold is exceeded, when
the threshold is exceeded retrieving a reading from the
accumulator; storing the accumulator reading and a reading of the
at least one of the accelerometer and the transducer; and
determining whether the reading is below the threshold, when the
reading is below the threshold, storing an indication of a REM end
and returning to sampling lid closure. In a further embodiment, the
method further includes: measuring a light level with at least one
photosensor present on the lens; storing the light level and
current reading from the accumulator; and determining when a change
in light level occurs and storing the current reading from the
accumulator with the light level reading. In a further embodiment
to the prior embodiment, the method further includes comparing the
accumulator to a duration threshold; when the accumulator is in
excess of the duration threshold, determining if the current light
level approximates the initial light level reading, when initial
light level is reached, terminating method. In a further embodiment
to any of the previous embodiments, sampling of the at least one of
the accelerometer and the transducer occurs at a first motion
sampling rate until the reading exceeds the threshold, then
sampling at a second motion sampling rate. In a further embodiment
to any of the previous embodiments, when lid closure is detected,
then sampling lid closure at a second lid sampling rate.
[0017] In at least one embodiment, a method for monitoring sleep
with a powered ophthalmic lens, the method includes: activating the
powered ophthalmic lens; initiating an accumulator on the lens to
track a passage of time; sampling at least once at least one of an
accelerometer and a transducer; and determining whether a first
threshold is exceeded, when the first threshold is exceeded
retrieving a reading from the accumulator, storing the accumulator
reading and a reading of the at least one of the accelerometer and
the transducer, and determining whether the reading is below a
second threshold, when the reading is below the second threshold,
storing an indication of a REM end and returning to sampling lid
closure. In a further embodiment, sampling of the at least one of
the accelerometer and the transducer occurs at a first motion
sampling rate until the reading exceeds the threshold, then
sampling at a second motion sampling rate.
[0018] In at least one embodiment, a method for monitoring sleep
with a powered ophthalmic lens, the method includes: activating the
powered ophthalmic lens; initiating an accumulator on the lens to
track a passage of time; sampling at least one of a lid position
sensor system and an eye movement sensor system; retrieving a
reading from the accumulator; storing an output of the lid position
sensor system, an output of the eye movement sensor system and the
accumulator reading in memory; and repeating the sampling,
retrieving and storing steps at a predetermined sampling rate. In a
further embodiment, the eye movement sensor system includes at one
of an accelerometer and a transducer. In a further embodiment to
either of the previous two embodiments, the method further
includes: measuring a light level with at least one photosensor
present on the lens; storing the light level and current reading
from the accumulator; and determining when a change in light level
occurs and storing the current reading from the accumulator with
the light level reading. In a further embodiment, the method
further includes: comparing the accumulator to a duration
threshold; when the accumulator is in excess of the duration
threshold, determining if the current light level approximates the
initial light level reading, when initial light level is reached,
terminating method. In a further embodiment to any of the
embodiments in this paragraph, when lid closure is detected, then
sampling lid closure at a second lid sampling rate.
[0019] In a further embodiment to any of the previous embodiments,
the method further includes: monitoring a power supply on the lens
for an available energy level; when the power supply has the
available energy level below a low energy threshold, performing at
least one of reducing the sampling rate for at least one of the
accelerometer and the transducer, reducing the sampling rate of at
least one sensor, terminating further sampling of at least one of
the accelerometer and the transducer, terminating further
monitoring of the power supply, storing a time stamp representing
low energy based on the current value in the accumulator, removing
power from at least one of the accelerometer and the transducer,
sampling the lid closure at a second lid sampling rate that is
slower than the first sampling rate, and powering a memory where
the readings are stored.
[0020] In a further embodiment to any of previous embodiments, the
method further includes: monitoring available memory for storing
readings; when the available memory is below a low memory
threshold, performing at least one of storing a time stamp
representing low memory based on the current value in the
accumulator, reducing the sampling rate for at least one of the
accelerometer and the transducer, terminating further sampling of
at least one of the accelerometer and the transducer, storing
future readings from at least one of the accelerometer and the
transducer over the earliest stored readings in the memory, and
deleting the stored sensor readings associated with the lowest
accumulator reading and shifting the remaining stored sensor and
accumulator readings in the memory.
[0021] In a further embodiment to any of previous embodiments,
storing the readings includes transmitting the readings to an
external device for storage. In a further embodiment, the external
device stores the readings with a time stamp based on the current
time on the external device. In a further embodiment to either of
the previous two embodiments, the method further includes sampling
light levels with the external device and storing the light level
with a time stamp in memory. In a further embodiment to any of the
previous three embodiments, the method further includes receiving
with the external device user input for initiation of a sleep study
and a termination of the sleep study.
[0022] In at least one embodiment, a powered ophthalmic lens, the
powered ophthalmic lens includes: a contact lens; an eyelid
position sensor system in the contact lens, the eyelid position
sensor system includes a sensor array having a plurality of
measurement points vertically spaced from each other to detect
eyelid position and a signal conditioner configured to sample the
measurement points in the sensor array to detect eyelid position
and provide an output lid signal; an eye movement sensor system in
the contact lens, the eye movement sensor system includes at least
one sensor to track and determine eye position and a signal
conditioner cooperatively associated with the sensor and configured
to track and determine eye position in spatial coordinates based on
information from the sensor output and provide an output movement
signal; a system controller electrically connected with said eyelid
position sensor system and said eye movement sensor system, said
system controller configured to sample said eyelid position sensor
system and said eye movement system based on at least one
predetermined sampling rate; and a memory in electrical
communication with said system controller, and wherein said system
controller stores data based on each sample in said memory.
[0023] In at least one embodiment, a powered ophthalmic lens
includes a contact lens; an eye movement sensor system in the
contact lens, the eye movement sensor system includes at least one
sensor to track and determine eye position and a signal conditioner
cooperatively associated with the sensor and configured to track
and determine eye position in spatial coordinates based on
information from the sensor output and provide an output movement
signal; a system controller electrically connected with said eye
movement sensor system, said system controller configured to sample
the eye movement sensor system based on at least one predetermined
sampling rate; and a data manager in electrical communication with
said system controller and having a memory, said data manager
configured to store data present in any signal outputted from said
system controller to said data manager in said memory. In a further
embodiment, the lens further includes an eyelid position sensor
system in the contact lens, the eyelid position sensor system
includes a sensor array having a plurality of measurement points
vertically spaced from each other to detect eyelid position and a
signal conditioner configured to sample the measurement points in
the sensor array to detect eyelid position and provide an output
lid signal; and wherein said system controller electrically
connected with said eyelid position sensor system, said system
controller configured to sample said eyelid position sensor system
based on at least one predetermined eyelid sampling rate.
[0024] Further to any of the above powered ophthalmic lens
embodiments, the lens further includes an accumulator; and said
system controller is configured to store a corresponding reading
from said accumulator for each sample data set stored. Further to
any of the above powered ophthalmic lens embodiments, the lens
further includes a power source electrically connected to said lid
position sensor system, said eye movement sensor system, and said
system controller; and a resource management system in electrical
communication with at least one of said power source and said
memory; said resource management system configured to determine at
least one of a low energy level and memory storage threshold
exceeded and in response to a positive determination, said resource
management system is configured to at least one of reduce all
sampling rates of the system, terminate all sampling of said eyelid
position sensor system and said eye movement system, and replace
earlier data with newer data when memory storage threshold is
exceeded.
[0025] Further to any of the above powered ophthalmic lens
embodiments, the lens further includes a communications system
configured to communicate with an external device. In a further
embodiment, the system controller transmits any received signal
output to the external device through said communications
system.
[0026] Further to any of the above powered ophthalmic lens
embodiments, the eye movement system includes at least one
accelerometer. In a further embodiment, the eye movement sensor
system signal conditioner provides an output when a signal from
said at least one accelerometer exceeds a movement threshold.
[0027] In at least one embodiment, a system includes any of the
above powered ophthalmic lens embodiments and a base station
capable of housing said lens, said base station includes a housing
having a cavity of sufficient size for at least one lens, a clock,
a communication system configured to communicate with any lens
inserted in said housing includes activating said lens and
downloading data stored in said memory in said lens; a memory
configured to store downloaded data; and means for communicating
with an external computer to transmit data received from said
memory in said lens.
[0028] The electronic ophthalmic lens with lid position sensor
and/or an eye movement sensor in accordance with the present
invention overcomes the limitations associated with the prior art
as briefly described above. These sensors may be integrated into a
contact lens instead of requiring a clinical environment or
spectacles as is common for existing eye-facing detection systems.
The sensors are of the appropriate size and current consumption for
use in a contact lens. The sensors also output the information
necessary for determining whether the wearer is asleep or
awake.
[0029] In accordance with one aspect, the present invention is
directed to a powered ophthalmic lens. The powered ophthalmic lens
includes a contact lens, an eyelid position sensor system
incorporated into the contact lens, an eye position sensor system,
a system controller, and a data manager. The eyelid position sensor
system includes a sensor array having at least one of a plurality
of individual sensors spaced vertically from each other and a
continuous pressure and/or capacitance sensor to detect eyelid
position. The eye position sensor system includes at least one
sensor to detect eye position. The system controller is configured
to sample each individual sensor in the sensor array to detect
eyelid position and provide an output control signal. The data
manager is configured to receive the output control signal and to
log data regarding sleep of the wearer. In at least one embodiment,
the contact lens includes an optic zone and a peripheral zone in
which the electrical components are located. In an alternative
embodiment, the eyelid position sensor system includes a strip
sensor in place of the plurality of individual sensors.
[0030] In accordance with yet another aspect, the present invention
is directed to a powered ophthalmic lens. The powered ophthalmic
lens includes an intraocular lens, an eyelid position sensor system
incorporated into the intraocular lens, an eye position sensor
system, a system controller, and a data manager. The eyelid
position sensor system includes a sensor array having a plurality
of individual sensors spaced vertically from each other to detect
eyelid position. The eye position sensor system includes at least
one sensor to detect eye position. The system controller is
configured to sample each individual sensor to provide an output
control signal. The data manager is configured to receive the
output control signal and to log data regarding sleep of the
wearer.
[0031] In at least one embodiment it will be advantageous to
provide a mechanism in which to track sleep by a worker.
[0032] The present invention relates to a powered or electronic
ophthalmic lens which may incorporate an eyelid or lid position
sensor and an eye position sensor. It is known that the eyelids
protect the globe in a number of ways, including the blink reflex
and the tear spreading action. The blink reflex of the eyelids
prevents trauma to the globe by rapidly closing upon a perceived
threat to the eye. Blinking also spreads tears over the globe's
surface to keep it moist and rinse away bacteria and other foreign
matter. But the movement of the eyelids may also indicate other
actions or functions at play. In at least one embodiment, an eyelid
position sensor may be utilized to determine whether the individual
wearing the electronic ophthalmic lens is asleep.
[0033] The present invention more generally relates to a powered
contact lens including an electronic system, which performs any
number of functions, including actuating a variable-focus optic if
included. The electronic system includes one or more batteries or
other power sources, power management circuitry, one or more
sensors, clock generation circuitry, control algorithms and
circuitry, and lens driver circuitry.
[0034] Control of a powered ophthalmic lens may be accomplished
through a manually operated external device that communicates with
the lens wirelessly, such as a hand-held remote unit. Alternately,
control of the powered ophthalmic lens may be accomplished via
feedback or control signals directly from the wearer. For example,
sensors built into the lens may detect blinks and/or blink
patterns. Based upon the pattern or sequence of blinks, the powered
ophthalmic lens may change operation state, for example, between an
awake operation state and an asleep operation state. Alternatively,
the sensors may include, for example, a pressure sensor, a reed
switch, a salinity sensor, a biosensor, and a capacitive sensor to
provide a signal indicating the lens has been inserted.
[0035] The blink detection algorithm in at least one embodiment is
a component of the system controller which detects characteristics
of blinks, for example, if the lid is open or closed, the duration
of the blink open or closed, the inter-blink duration, and the
number of blinks in a given time period. The algorithm in
accordance with at least one embodiment relies on sampling light
incident on the eye at a certain sample rate. Pre-determined blink
patterns are stored and compared to the recent history of incident
light samples. When patterns match, the blink detection algorithm
triggers activity in the system controller, for example, to switch
to a particular operation state.
[0036] The blink detection algorithm and associated circuitry in at
least one embodiment operates over a reasonably wide range of
lighting conditions and is preferably able to distinguish an
intentional blink sequence or closed eyelids from involuntary
blinks. It is also preferred that minimal training is required to
utilize intentional blinks to activate and/or control the powered
ophthalmic lens. The blink detection algorithm and associated
circuitry of the present invention provides a safe, low cost, and
reliable means and method for detecting blinks via a powered or
electronic contact lens, which also has a low rate of power
consumption and is scalable for incorporation into an ophthalmic
lens, for at least one of activating or controlling a powered or
electronic ophthalmic lens.
[0037] The present invention is also directed to a powered or
electronic ophthalmic lens that incorporates an eyelid or lid
position sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] The foregoing and other features and advantages of the
invention will be apparent from the following, more particular
description of preferred embodiments of the invention, as
illustrated in the accompanying drawings.
[0039] FIGS. 1A and 1B illustrate a contact lens having sensor
systems in accordance with at least one embodiment of the present
invention.
[0040] FIG. 2 illustrates a graphical representation of light
incident on the surface of the eye versus time, illustrating a
possible involuntary blink pattern recorded at various light
intensity levels versus time and a usable threshold level based on
some point between the maximum and minimum light intensity levels
in accordance with at least one embodiment of the present
invention.
[0041] FIG. 3 is a state transition diagram of an eyelid position
sensor system in accordance with at least one embodiment of the
present invention.
[0042] FIG. 4 illustrates a diagrammatic representation of a
photodetection path utilized to detect and sample received light
signals in accordance with at least one embodiment of the present
invention.
[0043] FIG. 5 illustrates a block diagram of digital conditioning
logic in accordance with at least one embodiment of the present
invention.
[0044] FIG. 6 illustrates a block diagram of digital detection
logic in accordance with at least one embodiment of the present
invention.
[0045] FIG. 7 illustrates a timing diagram in accordance with at
least one embodiment of the present invention.
[0046] FIGS. 8A and 8B illustrate diagrammatic representations of
digital system controllers in accordance with at least one
embodiment of the present invention.
[0047] FIGS. 9A through 9G illustrate timing diagrams for automatic
gain control in accordance with at least one embodiment of the
present invention.
[0048] FIG. 10 illustrates a diagrammatic representation of
light-blocking and light-passing regions on an integrated circuit
die in accordance with at least one embodiment of the present
invention.
[0049] FIG. 11 illustrates a diagrammatic representation of an
electronic insert, including a blink detector, for a powered
contact lens in accordance with at least one embodiment of the
present invention.
[0050] FIGS. 12A and 12B illustrate diagrammatic representations of
eyelid position sensors in accordance with at least one embodiment
of the present invention.
[0051] FIG. 13A illustrates a diagrammatic representation of two
eyelid position sensors having a communication channel for
synchronizing operation between two eyes in accordance with at
least one embodiment of the present invention.
[0052] FIG. 13B illustrates a diagrammatic representation of one
eyelid position sensor having a communication channel for
communicating with an external device in accordance with at least
one embodiment of the present invention.
[0053] FIG. 14A illustrates a diagrammatic representation of an
electronic system incorporated into a contact lens for detecting
eyelid position in accordance with at least one embodiment of the
present invention.
[0054] FIG. 14B illustrates an enlarged view of the electronic
system of FIG. 14A.
[0055] FIG. 15 illustrates a diagrammatic representation of outputs
from eyelid position sensors in accordance with at least one
embodiment of the present invention.
[0056] FIG. 16A illustrates a diagrammatic representation of
another electronic system incorporated into a contact lens for
detecting eyelid position in accordance with at least one
embodiment of the present invention.
[0057] FIG. 16B illustrates an enlarged view of the electronic
system of FIG. 16A.
[0058] FIG. 17A-17C illustrate diagrammatic representations of an
eyelid position detecting system in accordance with at least one
embodiment of the present invention.
[0059] FIG. 17D illustrates an enlarged view of the electronic
system of FIGS. 17A-17C.
[0060] FIG. 18A illustrates a diagrammatic representation of a
pupil position and convergence detection system incorporated into a
contact lens in accordance with at least one embodiment of the
present invention.
[0061] FIG. 18B is an enlarged view of the pupil position and
convergence detection system of FIG. 18A.
[0062] FIG. 18C illustrates an overlay of an X, Y, and Z axes on
the eye.
[0063] FIG. 19 illustrates a block diagram of an insertion sensor
embodiment in accordance with at least one embodiment of the
present invention.
[0064] FIG. 20 illustrates a block diagram of a generic system
having multiple sensors, a system controller and an alert
mechanism, wherein an activation decision is made based on the
output of two or more sensors in accordance with the present
invention.
[0065] FIG. 21 illustrates a flow chart of a method by which a
system controller determines if the state of an alert mechanism is
to be changed based upon sensor inputs in accordance with at least
one embodiment of the present invention.
[0066] FIG. 22 illustrates a block diagram of a storage box in
accordance with at least one embodiment of the present
invention.
[0067] FIG. 23 illustrates a flow chart of a method by which a
system controller monitors sleep in accordance with at least one
embodiment of the present invention.
[0068] FIG. 24 illustrates a flow chart of a method by which a
system controller monitors sleep in accordance with at least one
embodiment of the present invention.
[0069] FIG. 25 illustrates a flow chart of a method by which a
system controller monitors sleep in accordance with at least one
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0070] Conventional contact lenses are polymeric structures with
specific shapes to correct various vision problems as briefly set
forth above. To achieve enhanced functionality, various circuits
and components may be integrated into these polymeric structures.
For example, control circuits, microprocessors, communication
devices, power supplies, sensors, data manager, light-emitting
diodes, and miniature antennas may be integrated into contact
lenses via custom-built optoelectronic components to not only
correct vision, but to enhance vision as well as provide additional
functionality as is explained herein. Electronic and/or powered
contact lenses may be designed to provide enhanced vision via
zoom-in and zoom-out capabilities, or just simply modifying the
refractive capabilities of the lenses. Electronic and/or powered
contact lenses may be designed to enhance color and resolution, to
display textual information, to translate speech into captions in
real time, to offer visual cues from a navigation system, and to
provide image processing and internet access. The lenses may be
designed to allow the wearer to see in low light conditions. The
properly designed electronics and/or arrangement of electronics on
lenses may allow for projecting an image onto the retina, for
example, without a variable focus optic lens, provide novelty image
displays and even provide wakeup alerts. In addition, sensors built
into the lenses may be utilized to detect light incident on the eye
to compensate for ambient light conditions or for use in
determining blink patterns and whether the wearer is asleep or
awake.
[0071] The powered or electronic contact lens of at least one
embodiment includes the necessary elements to monitor sleep of the
wearer with or without elements to correct and/or enhance the
vision of patients with one or more of the above described vision
defects or otherwise perform a useful ophthalmic function. In
addition, the electronic contact lens may be utilized simply to
enhance normal vision or provide a wide variety of functionality as
described above. The electronic contact lens may have a
variable-focus optic lens, an assembled front optic embedded into a
contact lens or just simply embedding electronics without a lens
for any suitable functionality. The electronic lens of the present
invention may be incorporated into any number of contact lenses as
described above. In addition, intraocular lenses may also
incorporate the various components and functionality described
herein. However, for ease of explanation, the disclosure will focus
on an electronic contact lens intended for single-use daily
disposability.
[0072] The present invention may be employed in a powered
ophthalmic lens or powered contact lens having an electronic
system, which actuates a variable-focus optic or any other device
or devices configured to implement any number of numerous functions
that may be performed. The electronic system includes one or more
batteries or other power sources, power management circuitry, one
or more sensors, clock generation circuitry, control algorithms and
circuitry, and lens driver circuitry. The complexity of these
components may vary depending on the required or desired
functionality of the lens. Alternatively, the contact lens may just
monitor sleep of the wearer including rapid eye movement (REM)
sleep in at least one embodiment.
[0073] Control of an electronic or a powered ophthalmic lens may be
accomplished through a manually operated external device that
communicates with the lens, such as a hand-held remote unit. For
example, a fob may wirelessly communicate with the powered lens
based upon manual input from the wearer. Alternately, control of
the powered ophthalmic lens may be accomplished via feedback or
control signals directly from the wearer. For example, sensors
built into the lens may detect blinks, blink patterns, eyelid
closures, and/or eye movement. Based upon the pattern or sequence
of blinks and/or movement, the powered ophthalmic lens may change
operation state, for example, the operation state of the lens to
begin monitoring sleep by the wearer. A further alternative is that
the wearer has no control over operation of the powered ophthalmic
lens.
[0074] FIG. 1A illustrates a sleep monitoring system according to
at least one embodiment. The illustrated system includes an eyelid
position sensor system 110, an eye movement sensor system 120, a
system controller 132 and a data manager 134. The sensor systems
are in electrical communication with the system controller 132,
which in turn is in electrical communication with the data manager
134. In at least one embodiment, the data manager 134 includes an
accumulator connected to a memory. In at least one embodiment, the
data manager 134 is consolidated with the system controller
132.
[0075] The illustrated eyelid position sensor system 110 in FIG. 1B
includes at least one sensor in electrical communication with a
signal processing component(s). The at least one sensor allows for
the detection of eyelid closure and may take a variety of forms as
is discussed later in this disclosure.
[0076] The illustrated eye movement sensor system 120 in FIG. 1B
includes at least one sensor in electrical communication with a
signal processor. The at least one sensor may take a variety of
forms as is discussed later in this disclosure. Examples include an
accelerometer and a transducer.
[0077] In an alternative embodiment, an integrated circuit or other
electrical component that houses the system controller also houses
the signal processing of the two sensor systems.
[0078] FIG. 1A also illustrates a power source 130 that, in at
least one embodiment, provides power to the other components of the
system. FIG. 1A illustrates an optional resource management system
140, which will be discussed later.
[0079] The system controller in at least one alternate embodiment
uses a blink detection method which detects characteristics of
blinks, for example, is the lid open or closed, the duration of the
blink, the inter-blink duration, the number of blinks in a given
time period, and the length of lid closure. The method in
accordance with at least one embodiment relies on sampling light
incident on the eye at a certain sample rate. Pre-determined blink
patterns are stored and compared to the recent history of incident
light samples. When patterns match, the blink detection may trigger
activity in the system controller, for example, to activate sleep
monitoring or deactivate sleep monitoring. The blink detection in a
further embodiment distinguishes between the pre-determined blink
patterns and the eyelid movements associated with drowsiness or
sleep onset.
[0080] Blinking is the rapid closing and opening of the eyelids and
is an essential function of the eye. Blinking protects the eye from
foreign objects, for example, individuals blink when objects
unexpectedly appear in proximity to the eye. Blinking provides
lubrication over the anterior surface of the eye by spreading
tears. Blinking also serves to remove contaminants and/or irritants
from the eye. Normally, blinking is done automatically, but
external stimuli may contribute as in the case with irritants.
However, blinking may also be purposeful, for example, for
individuals who are unable to communicate verbally or with gestures
can blink once for yes and twice for no. The blink detection method
and system in one alternative embodiment utilizes blinking patterns
that cannot be confused with normal blinking response. In other
words, if blinking is to be utilized as a means for controlling an
action, then the particular pattern selected for a given action
cannot occur at random; otherwise inadvertent actions may occur. As
blink speed and/or frequency may be affected by a number of
factors, including fatigue, concentration, boredom, eye injury,
medication and disease, blinking patterns for control purposes
preferably account for these and any other variables that affect
blinking. The average length of involuntary blinks is in the range
of about one hundred (100) to four hundred (400) milliseconds.
Average adult men and women blink at a rate of ten (10) involuntary
blinks per minute, and the average time between involuntary blinks
is about 0.3 to seventy (70) seconds. Eyelid movements may also
indicate other conditions such as drowsiness as the eyelids have a
general trend towards closing over a period of time or are closed
for a period of time indicating that the wearer is asleep.
[0081] Blink detection may be summarized in the following
steps.
[0082] 1. Define an intentional "blink sequence" that a user will
execute for positive blink detection or that is representative of
sleep onset.
[0083] 2. Sample the incoming light level at a rate consistent with
detecting the blink sequence and rejecting involuntary blinks.
[0084] 3. Compare the history of sampled light levels to the
expected "blink sequence," as defined by a blink template of
values.
[0085] 4. Optionally implement a blink "mask" sequence to indicate
portions of the template to be ignored during comparisons, e.g.
near transitions. This may allow for a user to deviate from a
desired "blink sequence," such as a plus or minus one (1) error
window, wherein one or more of lens activation, control, and focus
change can occur. Additionally, this may allow for variation in the
user's timing of the blink sequence.
[0086] It should be appreciated that a variety of expected or
intended blink patterns may be programmed into a device with one or
more active at a time and in at least one embodiment control the
use of particular blink patterns to be used in a particular
operation state. More specifically, multiple expected or intended
blink patterns may be utilized for the same purpose or
functionality, or to implement different or alternate
functionality. For example, one blink pattern may be utilized to
cause the lens to change operation state between at least an asleep
operation state and an awake operation state. The blink detection
in at least one embodiment also can detect when the eyelids remain
closed, which would be detected as a continuous blink; the eyelids
have a movement trajectory to closing for sleep, which would be
detected as a partial blink or series of partial blinks such as
when a portion of the sensors are covered by an eyelid after a
blink has occurred; and eyelid droop, which would be detected as a
change in the steady state position of the upper and/or lower
eyelid from its normal steady state position, for example, with or
without confirmation of gaze position and/or head droop.
[0087] An example of a way to determine if the wearer is nodding
off is by tracking the length of blink period widths and eyelids
open period widths. Alternatively, also partial eyelids open period
widths are tracked in addition or instead of eyelids open period
widths. Typically the ratio will be 1:15 to 1:22 between blinks and
eyelids open, but as the wearer approaches sleep the length of
blink period widths will increase while eyelid open period widths
will decrease. In a system that includes a plurality of registers
for storing the period widths, a running series of ratios between
blink periods and eyelid open periods may be maintained such that
as that trend of ratios approaches a predetermined drowsy
threshold, the wearer is probably starting to doze off. Examples of
the predetermined drowsy threshold include, but are not limited to,
one to 1, 2, 3, 4, 5, and 10. The system controller would be
configured to compare the ratios and track the period lengths over
a rolling window. In an alternative embodiment, the system
controller would retain only period width information associated
with non-standard blinks for a predetermined window as the wearer
may notice they are dozing and be more attentive before having
another lengthy blink period. In at least one embodiment, when the
wearer is detected to be nodding off, the sampling frequency of the
sensor(s) may increase to increase the data resolution. In a
further embodiment, the data manager logs when a sampling frequency
is changed and in a still further embodiment, an identification of
the sampling frequency being used is stored.
[0088] In an alternative embodiment, the system controller would
determine a ratio of blink to eyelids open for the wearer at a
predetermined time(s). Examples of the predetermined time(s)
include, but are not limited to, shortly after lens insertion, one
hour increments, two hour increments, four hour increments and any
combination of these. In an alternative or further embodiment, the
system controller would determine a ratio of blink to eyelids open
for the wearer when a change of focus of one or both eyes is
detected or there is an increase in the time between blinks such
that the increase exceeds a predetermined threshold indicating, for
example, that the wearer is concentrating on something or boredom
has set in for the wearer. This wearer-specific ratio would be used
to calculate the predetermined drowsy threshold. An example of the
calculation includes taking a fraction of the wearer-specific
ratio, such as reducing by a quarter (e.g., 1:20 to 1:15), half
(e.g., 1:20 to 1:10) or three quarters (e.g., 1:20 to 1:5). Based
on this example, one of ordinary skill in the art should appreciate
that a variety of reductions are possible.
[0089] A further example of nodding off is the speed at which the
eyelids open and close during a blink. A study found that the mean
time for eyelid closure was 92 msec plus or minus 17 msec and the
mean time for eyelid opening was 242 msec plus or minus 55 msec.
BanderWerf, et al., "Eyelid Movements: Behavioral Studies of
Blinking in Humans under Different Stimulus Conditions," Journal of
Physiology, May 2003, vol. 89, no. 5, pp. 2784-2796. The system
controller in at least one embodiment maintains a running list of
times for at least one of eyelid closure and eyelid opening to
allow for a determination if there is a change in speed of the
monitored eyelid movement. Such that when the speed over a series
of blinks slows, then the system controller has a basis on which to
determine that the wearer is drowsy. In a further embodiment, the
speed is measured as a ratio between the distance from the closed
eyelid position and the open eyelid position and the time to travel
between these two points.
[0090] A still further example of nodding off is a decrease in the
Saccades movement of the pupil of the lens wearer. It is normal
when a person is awake that their eyes dart about in a Saccades
movement due to physiological considerations. As a person becomes
drowsy, these movements will decrease while the eyelids are open.
The eye movement sensor system in at least one embodiment is used
to track movement of the pupil and can provide this information to
the system controller for comparison along a running list of eye
movement data reflecting the volume, the length, and the speed of
pupil movement.
[0091] In a further embodiment, the system controller would utilize
signals from the accelerometer to determine if the wearer's head is
beginning to droop in conjunction with any longer blink period
width, then the system controller in at least one embodiment will
lower the drowsy threshold or alternatively use the drooping head
as confirmation that the wearer is beginning to doze off and
requires alerting.
[0092] FIG. 1B illustrates, in block diagram form, a contact lens
100 in accordance with at least one embodiment. In the illustrated
embodiment, the contact lens 100 includes an eyelid position system
110, an eye movement sensor system 120, a power source 130, a
system controller 132, and a data manager 134. The illustrated
eyelid position system 110 includes a photosensor 112, an amplifier
114, an analog-to-digital converter (or ADC) 116, and a digital
signal processor 118. The illustrated eye movement sensor system
120 includes a sensor 122 and a signal processor 124 such as an
acquisition sampling signal conditioner.
[0093] When the contact lens 100 is placed onto the front surface
of a user's eye the electronic circuitry of the blink detector
system may be utilized to implement the blink detection in at least
one embodiment. The photosensor 112, as well as the other
circuitry, is configured to detect blinks, various blink patterns
produced by the user's eye, and/or level of eyelid closure.
[0094] In this embodiment, the photosensor 112 may be embedded into
the contact lens 100 and receives ambient light 141, converting
incident photons into electrons and thereby causing a current,
indicated by arrow 113, to flow into the amplifier 114. The
photosensor or photodetector 112 may include any suitable device.
In one embodiment, the photosensor 112 includes a photodiode. In at
least one embodiment, the photodiode is implemented in a
complimentary metal-oxide semiconductor (CMOS process technology)
to increase integration ability and reduce the overall size of the
photosensor 112 and the other circuitry. The current 113 is
proportional to the incident light level and decreases
substantially when the photodetector 112 is covered by an eyelid.
The amplifier 114 creates an output proportional to the input, with
gain, and may function as a transimpedance amplifier which converts
input current into output voltage. The amplifier 114 may amplify a
signal to a usable level for the remainder of the system, such as
giving the signal enough voltage and power to be acquired by the
ADC 116. For example, the amplifier may be necessary to drive
subsequent blocks since the output of the photosensor 112 may be
quite small and may be used in low-light environments. The
amplifier 114 may be implemented as a variable-gain amplifier, the
gain of which may be adjusted by the system controller 132, in a
feedback arrangement, to maximize the dynamic range of the system.
In addition to providing gain, the amplifier 114 may include other
analog signal conditioning circuitry, such as filtering and other
circuitry appropriate to the photosensor 112 and amplifier 114
outputs. The amplifier 114 may include any suitable device for
amplifying and conditioning the signal output by the photosensor
112. For example, the amplifier 114 may include a single
operational amplifier or a more complicated circuit comprising one
or more operational amplifiers. The photosensor may be a switchable
array of photodiodes, and the amplifier may be an integrator. As
set forth above, the photosensor 112 and the amplifier 114 are
configured to detect and isolate blink sequences based upon the
incident light intensity received through the eye and convert the
input current into a digital signal usable ultimately by the system
controller 132. In at least one embodiment, the system controller
132 is preprogrammed or preconfigured to recognize various blink
sequences, blink patterns, an/or eyelid closures (partial or
complete) in various light intensity level conditions and provide
an appropriate output signal to the data manager 134. In at least
one embodiment, the system controller 132 also includes associated
memory.
[0095] In this embodiment, the ADC 116 may be used to convert a
continuous, analog signal output from the amplifier 114 into a
sampled, digital signal appropriate for further signal processing.
For example, the ADC 116 may convert an analog signal output from
the amplifier 114 into a digital signal that may be usable by
subsequent or downstream circuits, such as a digital signal
processor 118. The digital signal processor 118 may be utilized for
digital signal processing, including one or more of filtering,
processing, detecting, and otherwise manipulating/processing
sampled data to permit incident light detection for downstream use.
The digital signal processor 118 may be preprogrammed with the
blink sequences and/or blink patterns described above along with a
blink sequence indicating prolonged eyelid closure or eyelid drift.
The digital signal processor 118 also in at least one embodiment
includes associated memory, which in at least one embodiment stores
template and masks sets to detect, for example, blink patterns for
each operation state as selected by the system controller 132. The
digital signal processor 118 may be implemented utilizing analog
circuitry, digital circuitry, software, or a combination thereof.
In the illustrated embodiment, it is implemented in digital
circuitry. The ADC 116 along with the associated amplifier 114 and
digital signal processor 118 are activated at a suitable rate in
agreement with the sampling rate previously described, for example,
every one hundred (100) ms, which is subject to adjustment in at
least one embodiment.
[0096] In at least one embodiment, any suitable device that allows
for detection of movement of the eye and more particularly the
pupil may be utilized as the sensor 122, and more than a single
sensor 122 may be utilized. The output of the sensor 122 is
acquired, sampled, and conditioned by signal processor 124. The
signal processor 124 may include any number of devices including an
amplifier, a transimpedance amplifier, an analog-to-digital
converter, a filter, a digital signal processor, and related
circuitry to receive data from the sensor 122 and generate output
in a suitable format for the remainder of the system. The signal
processor 124 may be implemented utilizing analog circuitry,
digital circuitry, software, and/or a combination thereof. In at
least one embodiment, the signal processor 124 is co-designed with
the sensor 122, for example, circuitry for acquisition and
conditioning of an accelerometer are different than the circuitry
for a muscle activity sensor or optical pupil tracker. The output
of the signal processor 124 in at least one embodiment is a sampled
digital stream and may include absolute or relative position,
movement, detected gaze in agreement with convergence, or other
data. System controller 132 receives input from the position signal
processor 124 and uses this information, in conjunction with input
from the eyelid position sensor system, to determine whether the
wearer is asleep.
[0097] In at least one embodiment, the signal processors 118 and
124 are combined into (or fabricated as) one signal processor.
[0098] A power source 130 supplies power for numerous components in
the system. The power may be supplied from a battery, energy
harvester, or other suitable means as is known to one of ordinary
skill in the art. Essentially, any type of power source 130 may be
utilized to provide reliable power for all other components of the
system. A blink sequence in at least one embodiment may be utilized
to change the operation state of the system and/or the system
controller. Furthermore, the system controller 132 may control
other aspects of a powered contact lens depending on input from the
digital signal processor 118 and/or the signal processor 124, for
example, changing the focus or refractive power of an
electronically controlled lens through an actuator.
[0099] In at least one embodiment, the system controller 132 will
determine the operation state of the lens based on a received blink
pattern, for example, to initiate or terminate sleep monitoring
although in an alternative embodiment other operational states are
possible simultaneously or separately. Further to this embodiment
or alternatively, the operation state will determine a set of blink
templates and masks to be used by the digital signal processor 118
in that operation state along with control what the data manager
134 does in response to the system controller 132 detecting the
wearer has fallen asleep. In a further alternative embodiment, the
lens intended for use during a work shift will operate using just a
blink template indicating sleep onset and not change operational
state based on any blink pattern by the wearer.
[0100] The system controller 132 uses the signal from the
photosensor chain; namely, the photosensor 112, the amplifier 114,
the ADC 116 and the digital signal processing system 118, to
compare sampled light levels to determine eyelid closure and/or
blink activation patterns.
[0101] Referring to FIG. 2, a graphical representation of blink
pattern samples recorded at various light intensity levels versus
time and a usable threshold level is illustrated. Accordingly,
accounting for various factors may mitigate and/or prevent error in
detecting blinks when sampling light incident on the eye, such as
accounting for changes in light intensity levels in different
places and/or while performing various activities. Additionally,
when sampling light incident on the eye, accounting for the effects
that changes in ambient light intensity may have on the eye and
eyelid may also mitigate and/or prevent error in detecting blinks,
such as how much visible light an eyelid blocks when it is closed
in low-intensity light levels and in high-intensity light levels.
In other words, in order to prevent erroneous blinking patterns
from being utilized to control, the level of ambient light is
preferably accounted for as is explained in greater detail
below.
[0102] For example, in a study, it has been found that the eyelid
on average blocks approximately ninety-nine (99) percent of visible
light, but at lower wavelengths less light tends to be transmitted
through the eyelid, blocking out approximately 99.6 percent of
visible light. At longer wavelengths, toward the infrared portion
of the spectrum, the eyelid may block only thirty (30) percent of
the incident light. What is important to note; however, is that
light at different frequencies, wavelengths and intensities may be
transmitted through the eyelids with different efficiencies. For
example, when looking at a bright light source, an individual may
see red light with his or her eyelids closed. There may also be
variations in how much visible light an eyelid blocks based upon an
individual, such as an individual's skin pigmentation. As is
illustrated in FIG. 2, data samples of blink patterns across
various lighting levels are simulated over the course of a seventy
(70) second time interval wherein the visible light intensity
levels transmitted through the eye are recorded during the course
of the simulation, and a usable threshold value is illustrated. The
threshold is set at a value in between the peak-to-peak value of
the visible light intensity recorded for the sample blink patterns
over the course of the simulation at varying light intensity
levels. Having the ability to preprogram blink patterns while
tracking an average light level over time and adjusting a threshold
may be critical to being able to detect when an individual is
blinking, as opposed to when an individual is not blinking and/or
there is just a change in light intensity level in a certain
area.
[0103] Referring now again to FIGS. 1A and 1B, in further alternate
embodiments, the system controller 132 may receive input from
sources including one or more of a blink detector, pressure
sensors, an accelerometer(s), photosensors, and a fob control. By
way of generalization and based on this disclosure, one skilled in
the art should appreciate that the method of determining sleep by
the system controller 132 may use one or more inputs. For example,
an electronic or powered contact lens may be programmable specific
to an individual user, such as programming a lens to recognize both
of an individual's blink patterns and an individual's head
movements as detected with an accelerometer during the course of
the day, for example, head bobbing while the eyelids are closed. In
some embodiments, using more than one input to determine sleep by
an electronic contact lens, such as blink detection and head
movement, may give the ability for each method to be crosschecked
with another before sleep onset is determined to have occurred as
will be discussed later in connection with FIGS. 20 and 21. An
advantage of crosschecking may include mitigation of false
positives, such as minimizing the chance of unintentionally
triggering a lens to alert and/or record errant data. In one
embodiment, the crosschecking may involve a voting scheme, wherein
a certain number of conditions are met prior to a sleep
determination. In a further embodiment, the crosschecking may
involve a weighted average, wherein certain inputs will be deemed
more important than other inputs such as lid closure and head
orientation.
[0104] In an alternate embodiment, the system controller 132 may
output a signal indicating that the wearer has fallen asleep during
the asleep operation state, then the data manager 134 will record
the information in memory for later retrieval. In an alternative
embodiment, the system controller 132 stores the data in the memory
associated with the system controller 132 and does not use the data
manager 134 for data storage. As discussed later, in at least one
embodiment there is a clock such as an accumulator that provides a
time stamp. As set forth above, the powered lens of the present
invention may provide various functionalities.
[0105] FIGS. 3-17D provide examples of eyelid position sensor
systems and FIGS. 18A-18C provide an example of an eye movement
sensor system. In at least one embodiment, the eyelid position
sensor systems use blink detection to determine whether the eyelid
is closed and remains closed over a plurality of samples.
[0106] FIG. 3 illustrates a state transition diagram 300 for an
eyelid position sensor system in accordance with at least one
embodiment. The system starts in an IDLE state 302 waiting for an
enable signal bl_go to be asserted. When the enable bl_go signal is
asserted, for example, by an oscillator and control circuit which
pulses bl_go at a one hundred (100) ms rate commensurate with the
blink sampling rate, the state machine then transitions to a
WAIT_ADC state 304 in which an ADC is enabled to convert a received
light level to a digital value. The ADC asserts an adc_done signal
to indicate its operations are complete, and the system or state
machine transitions to a SHIFT state 306. In the SHIFT state 306
the system pushes the most recently received ADC output value onto
a shift register to hold the history of blink samples. In some
embodiments, the ADC output value is first compared to a threshold
value to provide a single bit (1 or 0) for the sample value, in
order to minimize storage requirements. The system or state machine
then transitions to a COMPARE state 308 in which the values in the
sample history shift register are compared to one or more blink
sequence templates and masks as described above. If a match is
detected, one or more output signals may be asserted, such as one
to switch the state of the lens to an asleep operation state or an
awake operation state or to signal onset of sleep by the wearer.
The system or state machine then transitions to the DONE state 310
and asserts a bl_done signal to indicate its operations are
complete.
[0107] FIG. 4 illustrates a photosensor or photodetector signal
path pd_rx_top that may be used to detect and sample received light
levels. The signal path pd_rx_top may include a photodiode 402, a
transimpedance amplifier 404, an automatic gain and low pass
filtering stage 406 (AGC/LPF), and an ADC 408. The adc_vref signal
is input to the ADC 408 from the power source 130 (see ADC 116 in
FIG. 1B) or alternately it may be provided from a dedicated circuit
inside the analog-to-digital converter 408. The output from the ADC
408, adc_data, is transmitted to the digital signal processing and
system controller block 118/132 (see FIG. 1B). Although illustrated
in FIG. 1B as individual blocks 118 and 132, for ease of
explanation, the digital signal processing and system controller
are implemented on a single block 410. The enable signal, adc_en,
the start signal, adc_start, and the reset signal, adc_rst_n are
received from the digital signal processing and system controller
410 while the complete signal, adc_complete, is transmitted
thereto. The clock signal, adc_clk, may be received from a clock
source external to the signal path, pd_rx_top, or from the digital
signal processing and system controller 410. It is important to
note that the adc_clk signal and the system clock may be running at
different frequencies. It is also important to note that any number
of different ADCs may be utilized in accordance with the present
invention which may have different interface and control signals
but which perform a similar function of providing a sampled,
digital representation of the output of the analog portion of the
photosensor signal path. The photodetect enable, pd_en, and the
photodetect gain, pd_gain, are received from the digital signal
processing and system controller 410.
[0108] FIG. 5 illustrates a block diagram of digital conditioning
logic 500 that may be used to reduce the received ADC signal value,
adc_data, to a single bit value pd_data. The digital conditioning
logic 500 may include a digital register 502 to receive the data,
adc_data, from the photodetection signal path pd_rx_top to provide
a held value on the signal adc_data_held. The digital register 502
is configured to accept a new value on the adc_data signal when the
adc_complete signal is asserted and to otherwise hold the last
accepted value when the adc_complete signal is received. In this
manner the system may disable the photodetection signal path once
the data is latched to reduce system current consumption. The held
data value may then be averaged, for example, by an
integrate-and-dump average or other averaging methods implemented
in digital logic, in the threshold generation circuit 504 to
produce one or more thresholds on the signal pd_th. The held data
value may then be compared, via comparator 506, to the one or more
thresholds to produce a one-bit data value on the signal pd_data.
It will be appreciated that the comparison operation may employ
hysteresis or comparison to one or more thresholds to minimize
noise on the output signal pd_data. The digital conditioning logic
may further comprise a gain adjustment block pd_gain_adj 508 to set
the gain of the automatic gain and low-pass filtering stage 406 in
the photodetection signal path via the signal pd_gain, illustrated
in FIG. 4, according to the calculated threshold values and/or
according to the held data value. It is important to note that in
this embodiment six bit words provide sufficient resolution over
the dynamic range for blink detection while minimizing complexity.
FIG. 5 illustrates an alternative embodiment that includes
providing a pd_gain_sdi control signal from, for example, the
serial data interface that allows one to override the automatic
gain control determined by gain adjustment block pd_gain_adj
508.
[0109] In one embodiment, the threshold generation circuit 504
includes a peak detector, a valley detector and a threshold
calculation circuit. In this embodiment, the threshold and gain
control values may be generated as follows. The peak detector and
the valley detector are configured to receive the held value on
signal adc_data_held. The peak detector is further configured to
provide an output value, pd_pk, which quickly tracks increases in
the adc_data_held value and slowly decays if the adc_data_held
value decreases. The operation is analogous to that of a classic
diode envelope detector, as is well-known in the electrical arts.
The valley detector is further configured to provide an output
value pd_vl which quickly tracks decreases in the adc_data_held
value and slowly decays to a higher value if the adc_data_held
value increases. The operation of the valley detector is also
analogous to a diode envelope detector, with the discharge resistor
tied to a positive power supply voltage. The threshold calculation
circuit is configured to receive the pd_pl and pd_vl values and is
further configured to calculate a mid-point threshold value
pd_th_mid based on an average of the pd_pk and pd_vl values. The
threshold generation circuit 504 provides the threshold value pd_th
based on the mid-point threshold value pd_th_mid.
[0110] The threshold generation circuit 504 may be further adapted
to update the values of the pd_pk and pd_vl levels in response to
changes in the pd_gain value. If the pd_gain value increases by one
step, then the pd_pk and pd_vl values are increased by a factor
equal to the expected gain increase in the photodetection signal
path. If the pd_gain value decreases by one step, then the pd_pk
and pd_val values are decreased by a factor equal to the expected
gain decrease in the photodetection signal path. In this manner the
states of the peak detector and valley detectors, as held in the
pd_pk and pd_vl values, respectively, and the threshold value pd_th
as calculated from the pd_pk and pd_vl values are updated to match
the changes in signal path gain, thereby avoiding discontinuities
or other changes in state or value resulting only from the
intentional change in the photodetection signal path gain.
[0111] In a further embodiment of the threshold generation circuit
504, the threshold calculation circuit may be further configured to
calculate a threshold value pd_th_pk based on a proportion or
percentage of the pd_pk value. In at least one embodiment the
pd_th_pk may be advantageously configured to be seven eighths of
the pd_pk value, a calculation which may be implemented with a
simple right shift by three bits and a subtraction as is well-known
in the relevant art. The threshold calculation circuit may select
the threshold value pd_th to be the lesser of pd_th_mid and
pd_th_pk. In this manner, the pd_th value will never be equal to
the pd_pk value, even after long periods of constant light incident
on the photodiode which may result in the pd_pk and pd_vl values
being equal. It will be appreciated that the pd_th_pk value ensures
detection of a blink after long intervals. The behavior of the
threshold generation circuit is further illustrated in FIG. 9, as
discussed subsequently.
[0112] FIG. 6 illustrates a block diagram of digital detection
logic 600 that may be used to implement digital blink detection in
accordance with at least one embodiment. The digital detection
logic 600 may include a shift register 602 adapted to receive the
data from the photodetection signal path pd_rx_top, FIG. 4, or from
the digital conditioning logic, FIG. 5, as illustrated here on the
signal pd_data, which has a one bit value. The shift register 602
holds a history of the received sample values, here in a 24-bit
register. The digital detection logic 600 further includes a
comparison block 604, adapted to receive the sample history and one
or more templates bl_tpl and masks bl_mask based on operation state
(if necessary), and is configured to indicate a match to the one or
more templates and masks on one or more output signals that may be
held for later use. In at least one embodiment, the operation state
determines the set of templates bl_tpl and masks bl_mask to be used
by the comparison block 604. In at least one set of the templates
bl_tpl, there is at least one sleep template representative of the
wearer falling asleep. In an alternative embodiment, the digital
detection logic 600 includes a comparison block, adapted to contain
one or more sleep templates, and is configured to indicate a match
to the one or more templates and masks on one or more output
signals that may be held for later use. In such an alternative
embodiment, the lens does not have asleep and awake operation
states.
[0113] The output of the comparison block 604 is latched via a D
flip-flop 606. The digital detection logic 600 may further include
a counter 608 or other logic to suppress successive comparisons
that may be on the same sample history set at small shifts due to
the masking operations. In a preferred embodiment the sample
history is cleared or reset after a positive match is found, thus
requiring a full, new matching sequence to be sampled before being
able to identify a subsequent match. The digital detection logic
600 may still further include a state machine or similar control
circuitry to provide the control signals to the photodetection
signal path and the ADC. In some embodiments the control signals
may be generated by a control state machine that is separate from
the digital detection logic 600. This control state machine may be
part of the digital signal processing and system controller
410.
[0114] In an alternative embodiment, the system determines sleep
based on the number of cycles that the eyelid(s) remain close. The
system would reset a counter, for example, a register, to zero or
one, depending upon the implementation, once the eyelid(s) is
detected as close. For each cycle that the eyelid(s) remains
closed, the counter is incremented by one. When the counter reaches
a predetermined threshold, the determination is made that the
wearer is asleep. Conversely, the counter could be reset to a
number equal to the threshold value and decrement for each cycle
that the eyelid(s) remain closed until the counter reaches zero or
one, depending upon the implementation used.
[0115] FIG. 7 illustrates a timing diagram of the control signals
provided from a detection subsystem to an ADC 408 (FIG. 4) used in
a photodetection signal path. The enable and clock signals adc_en,
adc_rst_n and adc_clk are activated at the start of a sample
sequence and continue until the analog-to-digital conversion
process is complete. In one embodiment the ADC conversion process
is started when a pulse is provided on the adc_start signal. The
ADC output value is held in an adc_data signal and completion of
the process is indicated by the analog-to-digital converter logic
on an adc_complete signal. Also illustrated in FIG. 7 is the
pd_gain signal which is utilized to set the gain of the amplifiers
before the ADC. This signal is shown as being set before the
warm-up time to allow the analog circuit bias and signal levels to
stabilize prior to conversion.
[0116] FIG. 8A illustrates a digital system controller 800 having a
digital blink detection subsystem dig_blink 802. The digital blink
detection subsystem dig_blink 802 may be controlled by a master
state machine dig_master 804 and may be adapted to receive clock
signals from a clock generator clkgen 806 external to the digital
system controller 800. The digital blink detection subsystem
dig_blink 802 may be adapted to provide control signals to and
receive signals from a photodetection subsystem as described above.
The digital blink detection subsystem dig_blink 802 may include
digital conditioning logic and digital detection logic as described
above, in addition to a state machine to control the sequence of
operations in a blink detection algorithm. The digital blink
detection subsystem dig_blink 802 may be adapted to receive an
enable signal from the master state machine 804 and to provide a
completion or done indication and a blink detection indication back
to the master state machine 804. In at least one embodiment, the
blink detection provides an indication when the wearer is drowsy as
referenced previously. In at least one embodiment, the blink data
is stored in a buffer such that upon detection of sleep by the
system, the data in the buffer may be transferred and stored in
memory for later analysis, for example, correlations between being
overly attentive prior to sleep and poor sleep quality.
[0117] In an alternative embodiment, FIG. 8B illustrates a digital
system controller 850 comprising a digital sleep detection
subsystem dig_sleep 852. The digital sleep detection subsystem
dig_sleep 852 may be controlled by a master state machine
dig_master 854 and may be adapted to receive clock signals from a
clock generator clkgen 856 external to the digital system
controller 850. The digital sleep detection subsystem dig_sleep 852
may be adapted to provide control signals to and receive signals
from a photodetection subsystem as described above. The digital
sleep detection subsystem dig_sleep 852 may include digital
conditioning logic and digital detection logic as described above,
in addition to a state machine to control the sequence of
operations in a sleep detection algorithm. The digital sleep
detection subsystem dig_sleep 852 may be adapted to receive an
enable signal from the master state machine 854 and to provide a
completion or done indication and a sleep detection indication back
to the master state machine 854.
[0118] In an alternative embodiment to either of the embodiments
illustrated in FIGS. 8A and 8B, a time clock is connected to the
clock generator 806 to track time since the lens began operation
and provide a time stamp signal to the data manager in an
embodiment where the data manager records data regarding the
initiation and termination of sleep by the wearer such that when
data is transmitted (or sent) from the lens to an external device
using, for example, at least one electronic communication
component, the external device is able to determine what time
periods the wearer was asleep while wearing the lens by reverse
calculating the time of day based on the time stamp from the lens
and the current time on the external device when the data is
transmitted as compared to the logged time stamps.
[0119] FIGS. 9A-9G depict waveforms to illustrate the operation of
the threshold generation circuit and automatic gain control (FIG.
5). FIG. 9A illustrates an example of photocurrent versus time as
might be provided by a photodiode in response to varying light
levels. In the first portion of the plot, the light level and
resulting photocurrent are relatively low compared to in the second
portion of the plot. In both the first and second portions of the
plot a double blink is seen to reduce the light and photocurrent.
Note that the attenuation of light by the eyelid may not be one
hundred (100) percent, but a lower value depending on the
transmission properties of the eyelid for the wavelengths of light
incident on the eye. FIG. 9B illustrates the adc_data_held value
that is captured in response to the photocurrent waveform of FIG.
9A. For simplicity, the adc_data_held value is illustrated as a
continuous analog signal rather than a series of discrete digital
samples. It will be appreciated that the digital sample values will
correspond to the level illustrated in FIG. 9B at the corresponding
sample times. The dashed lines at the top and bottom of the plot
indicate the maximum and minimum values of the adc_data and
adc_data_held signals. The range of values between the minimum and
maximum is also known as the dynamic range of the adc_data signal.
As discussed below, the photodection signal path gain is different
(lower) in the second portion of the plot. In general the
adc_data_held value is directly proportional to the photocurrent,
and the gain changes only affect the ration or the constant of
proportionality. FIG. 9C illustrates the pd_pk, pd_vl and pd_th_mid
values calculated in response to the adc_data_held value by the
threshold generation circuit. FIG. 9D illustrates the pd_pk, pd_vl
and pd_th_pk values calculated in response to the adc_data_held
value in some embodiments of the threshold generation circuit. Note
that the pd_th_pk value is always some proportion of the pd_pk
value. FIG. 9E illustrates the adc_data_held value with the
pd_th_mid and pd_th_pk values. Note that during long periods of
time where the adc_data_held value is relatively constant the
pd_th_mid value becomes equal to the adc_data_held value as the
pd_vl value decays to the same level. The pd_th_pk value always
remains some amount below the adc_data_held value. Also illustrated
in FIG. 9E is the selection of pd_th where the pd_th value is
selected to be the lower of pd_th_pk and pd_th_mid. In this way the
threshold is always set some distance away from the pd_pk value,
avoiding false transitions on pd_data due to noise on the
photocurrent and adc_data held signals. FIG. 9F illustrates the
pd_data value generated by comparison of the adc_data_held value to
the pd_th value. Note that the pd_data signal is a two-valued
signal which is low when a blink is occurring. FIG. 9G illustrates
a value of tia_gain versus time for these example waveforms. The
value of tia_gain is set lower when the pd_th starts to exceed a
high threshold shown as agc_pk_th in FIG. 9E. It will be
appreciated that similar behavior occurs for raising tia_gain when
pd_th starts to fall below a low threshold. Looking again at the
second portion of each of the FIGS. 9A through 9E the effect of the
lower tia_gain is clear. In particular note that the adc_data_held
value is maintained near the middle of the dynamic range of the
adc_data and adc_data_held signals. Further, it is important to
note that the pd_pk and pd_vl values are updated in accordance with
the gain change as described above such that discontinuities are
avoided in the peak and valley detector states and values due
solely to changes in the photodetection signal path gain.
[0120] FIG. 10 illustrates light-blocking and light-passing
features on an integrated circuit die 1000. The integrated circuit
die 1000 includes a light passing region 1002, a light blocking
region 1004, bond pads 1006, passivation openings 1008, and light
blocking layer openings 1010. The light-passing region 1002 is
located above the photosensors (not illustrated), for example, an
array of photodiodes implemented in the semiconductor process. In
at least one embodiment, the light-passing region 1002 permits as
much light as possible to reach the photosensors thereby maximizing
sensitivity. This may be done through removing polysilicon, metal,
oxide, nitride, polyimide, and other layers above the
photoreceptors, as permitted in the semiconductor process utilized
for fabrication or in post-processing. The light-passing area 1002
may also receive other special processing to optimize light
detection, for example, an anti-reflective coating, filter, and/or
diffuser. The light-blocking region 1004 may cover other circuitry
on the die which does not require light exposure. The performance
of the other circuitry may be degraded by photocurrents, for
example, shifting bias voltages and oscillator frequencies in the
ultra-low current circuits required for incorporation into contact
lenses, as mentioned previously. The light-blocking region 1004 is
formed with a thin, opaque, reflective material, for example
aluminum or copper already used in semiconductor wafer processing
and post-processing. If implemented with metal, the material
forming the light-blocking region 1004 must be insulated from the
circuits underneath and the bond pads 1006 to prevent short-circuit
conditions. Such insulation may be provided by the passivation
already present on the die as part of normal wafer passivation,
e.g. oxide, nitride, and/or polyimide, or with other dielectric
added during post-processing. Masking permits light blocking layer
openings 1010 so that conductive light-blocking metal does not
overlap bond pads on the die. The light-blocking region 1004 is
covered with additional dielectric or passivation to protect the
die and avoid short-circuits during die attachment. This final
passivation has passivation openings 1008 to permit connection to
the bond pads 1006.
[0121] In an alternative embodiment where the contact lens includes
tinting capabilities, the light-passing region 1002 is at least
partially overlapping with the region of the contact lens capable
of being tinted. Where the photosensors are present in both the
tinting region and non-tinting regions of the contact lens, it
allows for a determination of the amount of light being blocked by
the tinting. In a further embodiment, the entire light-passing
region 1002 is present in the tinting region.
[0122] FIG. 11 illustrates a contact lens with an electronic insert
having an eyelid position sensor system in accordance with the
present embodiments (invention). The contact lens 1100 includes a
soft plastic portion 1102 which provides an electronic insert 1104.
This insert 1104 includes a lens 1106 which is activated by the
electronics, for example, focusing near or far depending on
activation. In the illustrated embodiment, integrated circuit 1108
mounts onto the insert 1104 and connects to batteries 1110, lens
1106, and other components as necessary for the system. The
integrated circuit 1108 includes a photosensor 1112 and associated
photodetector signal path circuits. The photosensor 1112 faces
outward through the lens insert and away from the eye, and is thus
able to receive ambient light. The photosensor 1112 may be
implemented on the integrated circuit 1108 (as shown), for example,
as a single photodiode or array of photodiodes. The photosensor
1112 may also be implemented as a separate device mounted on the
insert 1104 and connected with wiring traces 1114. When the eyelid
closes, the lens insert 1104 including photodetector 1112 is
covered, thereby reducing the light level incident on the
photodetector 1112. The photodetector 1112 is able to measure the
ambient light to determine if the user is blinking or not. Based on
this disclosure one of ordinary skill in the art should appreciate
that photodetector 112 may be replaced or augmented by the other
sensors discussed in this disclosure.
[0123] Additional embodiments of the blink detection method may
allow for more variation in the duration and spacing of the blink
sequence, for example, by timing the start of a second blink based
on the measured ending time of a first blink rather than by using a
fixed template or by widening the mask "don't care" intervals (0
values).
[0124] It will be appreciated that blink detection and/or sleep
detection may be implemented in digital logic or in software
running on a microcontroller. The algorithm logic or
microcontroller may be implemented in a single application-specific
integrated circuit, ASIC, with photodetection signal path circuitry
and a system controller, or it may be partitioned across more than
one integrated circuit.
[0125] It is known that the eyelids protect the globe in a number
of ways, including the blink reflex and the tear spreading action.
The blink reflex of the eyelids prevents trauma to the globe by
rapidly closing upon a perceived threat to the eye. Blinking also
spreads tears over the globe's surface to keep it moist and rinse
away bacteria and other foreign matter. But the movement of the
eyelids may also indicate other actions or functions at play beyond
being used to track when an individual (or wearer) wearing an
electronic ophthalmic lens has fallen asleep. It is also important
to note that the sensed data, in addition to or in alternate use
may simply be utilized as part of a triggering event rather than as
a collection process. In other words, it should also be appreciated
that a device utilizing such a sensor may not change state in a
manner visible to the user; rather the device may simply log
data.
[0126] Referring now to FIG. 12A, there is illustrated an eyelid
position sensor system on an eye 1200. The system is incorporated
into a contact lens 1202. The top and bottom eyelids are shown,
with the top eyelid having possible locations 1201, 1203, and 1205
in order of increasing closure. The bottom eyelid is also
illustrated with levels of closure corresponding to the top eyelid;
namely, locations 1207, 1209 and 1205. When the eyelids are closed,
they occupy the same position; namely, 1205. The contact lens 1202
in accordance with the embodiment includes a sensor array 1204.
This sensor array 1204 includes one or more photosensors. In this
embodiment, the sensor array 1204 includes twelve (12) photosensors
1206a-1206l. With the top eyelid at position 1201 and the bottom
eyelid at position 1207, all photosensors 1206a-1206l are exposed
and receive ambient light, thereby creating a photocurrent which
may be detected by an electronic circuit described herein. With the
eyelids partially closed at positions 1203 and 1209, the top and
bottom photosensors 1206a and 1206b are covered, receive less light
than the other photosensors 1206c-1206l, and output a
correspondingly lower current which may be detected by the
electronic circuit. With the eyelids totally closed in position
1205, all sensors 1206a-1206l are covered with a corresponding
reduction in current. This system may be used to detect eyelid
position by sampling each photosensor in the sensor array and using
the photocurrent output versus sensor position to determine eyelid
position, for example, if the upper and lower eyelids do not fully
open after blinks indicating potential onset of sleep or fatigue.
It will be appreciated that the photosensors should be placed in
suitable locations on the contact lens, for example, providing
enough sample locations to reliably determine eyelid position while
not obstructing the clear optic zone (roughly the area occupied by
a dilated pupil.) This system may also be used to detect blinks by
routinely sampling the sensors and comparing measurements over
time. In an alternative embodiment, photosensors 1206a'-1206l' of a
sensor array 1204' form an arcuate pattern around the pupil while
being vertically spaced from each other as illustrated, for
example, in FIG. 12B. Under either of the illustrated embodiment,
one of ordinary skill in the art should appreciate that a number
other than 12 may be used in the sensor array. Further examples
include a number in a range of 3 through 15 (including the end
points in at least one embodiment), and more particularly a number
in a range of 4 through 8 (including the end points in at least one
embodiment).
[0127] FIG. 13A illustrates a system in which two eyes 1300 are at
least partially covered with contact lenses 1302. Sensor arrays
1304 are present in both of the contact lenses 1302 to determine
eyelid position, as previously described with respect to FIG. 12A.
In this embodiment, the contact lenses 1302 each have an electronic
communication component 1306. Electronic communication component
1306 in each contact lens 1302 permits two-way communication to
take place between the contact lenses 1302. The electronic
communication components 1306 may include radio frequency (RF)
transceivers, antennas, interface circuitry for photosensors 1308,
and associated or similar electronic components. The communication
channel represented by line 1310 may be RF transmissions at the
appropriate frequency and power with an appropriate data protocol
to permit effective communication between the contact lenses 1302.
Transmission of data between the two contact lenses 1302 may, for
example, verify that both eyelids have closed in order to detect a
true, purposeful eyelid closure rather than a wink, involuntary
blink, or squinting with one eye. The transmission may also allow a
system to determine if both eyelids have closed by a similar
amount, for example, that which is associated with a user reading
up-close. Data transmission may also take place to an external
device, for example, spectacle glasses, a patch worn on the user's
temple, or a smartphone (or other processor based system). In at
least one embodiment, the electronic communication components allow
for the transmission of logged sleep data to the smartphone (or
other external device). As such the electronic communication
components 1306 may be present on just one lens in at least one
alternative embodiment. In an alternative embodiment, an
accelerometer present in the smartphone (or other accelerometer
equipped device with transmission capability) worn by the
individual provides movement data for use in crosschecking a sleep
determination such as a lack of general movement is indicative of
the possibility of sleep or data indicative of the individual being
stationary.
[0128] In an alternative embodiment, the external device 1390,
illustrated in FIG. 13B, receives and stores data relating to sleep
as determined by the contact lens 1300 through at least one
electronic communication component 1392, which allows for
communication with the electronic communication component 1306 on
the contact lens 1300. One advantage to using an external device is
that the external device may keep track of time more accurately
than the contact lens while providing sufficient memory for a
faster sampling rate without concern of filling up memory on the
contact lens. More accurate time keeping will provide a data set
allowing for more accurate analysis.
[0129] In a further or alternative embodiment, the external device
provides a mechanism for the wearer to indicate when to initiate a
sleep study and/or termination of the sleep study. One example is
by displaying a graphical user interface on the external device
that includes a virtual button to be touched by the user.
[0130] FIGS. 14A and 14B illustrate an electronic system 1400 in
which eyelid position photosensors, as set forth above, are used to
trigger activity in a contact lens 1402 or more specifically, a
powered or electronic ophthalmic lens. FIG. 14A shows the
electronic system 1400 on the lens 1402, and FIG. 14B is an
exploded view of the system 1400. Light 1401 is incident onto one
or more photosensors 1404 as previously described with respect to
FIG. 12. These photosensors 1404 may be implemented with
photodiodes, cadmium sulfide (CdS) sensors, or other technologies
suitable for converting ambient light into current. Depending on
the choice of photosensors 1404, amplifiers 1406 or other suitable
circuitry may be required to condition the input signals for use by
subsequent or downstream circuits. A multiplexer 1408 permits a
single analog-to-digital converter (or ADC) 1410 to accept inputs
from multiple photosensors 1404. The multiplexer 1408 may be placed
immediately after the photosensors 1404, before the amplifiers
1406, or may not be used depending on considerations for current
consumption, die size, and design complexity. Since multiple
photosensors 1404 are needed at various positions on the eye to
detect eyelid position, sharing downstream processing components
(for example amplifiers, an analog-to-digital converter, and
digital signed processors) may significantly reduce the size needed
for the electronic circuitry. The amplifiers 1406 create an output
proportional to the input, with gain, and may function as
transimpedance amplifiers which convert input current into output
voltage. The amplifiers 1406 may amplify a signal to a usable level
for the remainder of the system, such as giving the signal enough
voltage and power to be acquired by the ADC 1410. For example, the
amplifiers 1406 may be necessary to drive subsequent blocks since
the output of the photosensors 1404 may be quite small and may be
used in low-light environments. Amplifiers 1406 may also be
implemented as variable-gain amplifiers, the gain of which may be
adjusted by a system controller 1412 to maximize the dynamic range
of the system 1400. In addition to providing gain, the amplifiers
1406 may include other analog signal conditioning circuitry, such
as filtering and other circuitry appropriate to the photosensor
1404 and amplifier 1406 output. The amplifiers 1406 may be any
suitable device for amplifying and conditioning the signal output
by the photosensor 1404. For example, the amplifiers 1404 may
simply be a single operational amplifier or a more complicated
circuit comprising one or more operational amplifiers.
[0131] As set forth above, the photosensors 1404 and the amplifiers
1406 are configured to detect incident light 1401 at various
positions on the eye and convert the input current into a digital
signal usable ultimately by the system controller 1412. In at least
one embodiment, the system controller 1412 is preprogrammed to
sample each photosensor 1404 on the eye to detect eyelid position
and provide an appropriate output signal to data manager 1414. The
system controller 1412 also includes associated memory. The system
controller 1412 may combine recent samples of the photosensors 1404
to preprogrammed patterns correlating to eyelid open and squinting
positions. For example, when the pattern matches that of both
eyelids partially closing associated with fatigue, the system
controller 1412 may trigger the data manager 1414 to log data.
Recording a user's eyelid patterns under various ambient light and
focal distance situations may be required to program the system
controller 1412 for reliable detection. The system 1400 may need to
differentiate between eyelid position changes, normal changes in
ambient light, shadows, and other phenomena. This differentiation
may be accomplished through proper selection of the sampling
frequency, amplifier gain, and other system parameters,
optimization of sensors placement in the contact lens,
determination of eyelid position patterns, recording ambient light,
comparing each photosensor to adjacent and all photosensors, and
other techniques to discern eyelid position uniquely.
[0132] In this embodiment, the ADC 1410 may be used to convert a
continuous, analog signal output from the amplifiers 1406 through
the multiplexer into a sampled, digital signal appropriate for
further signal processing. For example, the ADC 1410 may convert an
analog signal output from the amplifiers 1406 into a digital signal
that may be useable by subsequent or downstream circuits, such as a
digital signal processing system or microprocessor 1416. A digital
signal processing system or digital signal processor 1416 may be
utilized for digital signal processing, including one or more of
filtering, processing, detecting, and otherwise
manipulating/processing sampled data to permit incident light
detection for downstream use. The digital signal processor 1416 may
be preprogrammed with various eyelid position and/or closure
patterns. The digital signal processor 1416 also includes
associated memory in at least one embodiment. The digital signal
processor 1416 may be implemented utilizing analog circuitry,
digital circuitry, software, and/or a combination thereof. The ADC
1410 along with the associated amplifiers 1406 and digital signal
processor 1416 are activated at a suitable rate in agreement with
the sampling rate previously described, for example, every one
hundred (100) ms.
[0133] A power source 1418 supplies power for numerous components
including the eyelid position sensor system 1400. The power source
1418 may also be utilized to supply power to other components on
the contact lens. The power may be supplied from a battery, energy
harvester, or other suitable means as is known to one of ordinary
skill in the art. Essentially, any type of power source 1418 may be
utilized to provide reliable power for all other components of the
system. An eyelid position sensor array pattern, processed from
analog to digital, may enable activation of the system controller
1412 or a portion of the system controller 1412. Furthermore, the
system controller 1412 may control other aspects of a powered
contact lens depending on input from the digital signal processor
1408, for example, activating the data manager 1414.
[0134] Referring now to FIG. 15 there is illustrated an output
characteristic for three photosensors positioned at three different
vertical positions on the contact lens. The output characteristics
may represent the current proportional to incident light on each
photosensor or may represent a downstream signal, for example,
digital sampled data values versus time at the output of the ADC
(element 1410 in FIG. 14B). Total incident light 1502 increases,
holds steady, and then decreases, for example, when walking from a
dark room to a bright hallway then back to a dark room. All three
photosensors 1504, 1506, and 1508 would output a signal similar to
that of the ambient light if the eyelid remained open, illustrated
by dotted lines 1501 and 1503 for photosensors 1504 and 1508. In
addition to the ambient light level 1502 changing, partial closure
of the eyelids is indicated by position 1510, different than that
of the lid open positions 1512 and 1514. When the lid partially
closes, upper photosensor 1504 becomes covered by the upper eyelid
and outputs a correspondingly lower level due to obstruction of the
photosensor by the eyelid. Despite ambient light 1502 increasing,
photosensor 1504 receives less light and outputs a lower signal due
to the partially closed eyelid. A similar response is observed with
photosensor 1508 which becomes covered. Middle sensor 1506 is not
covered during squinting and thus continues to see the light level
increase, with a corresponding increase in output level. While this
example illustrates one particular case, it should be apparent how
various configurations of sensor position and eyelid movement could
be detected.
[0135] FIGS. 16A and 16B illustrate an alternate detection system
1600 incorporated into a contact lens 1602. FIG. 16A illustrates
the system 1600 on the contact lens 1602 and FIG. 16B illustrates
an exploded view of the system 1600. In this embodiment, capacitive
touch sensors 1604 are utilized instead of photosensors. In an
alternative embodiment, capacitive touch sensors 1604 are utilized
in addition to photosensors. Capacitive touch sensors are common in
the electronics industry, for example, in touch-screen displays.
The basic principle is that a variable capacitor 1604 is
implemented in a physical manner such that the capacitance varies
with proximity or touch, for example, by implementing a grid
covered by a dielectric. Sensor conditioners 1606 create an output
signal proportional to the capacitance, for example, by measuring
the change in an oscillator having the variable capacitor or by
sensing the ratio of the variable capacitor to a fixed capacitor
with a fixed-frequency AC signal. The output of the sensor
conditioners 1606 may be combined with a multiplexer 1608 to reduce
downstream circuitry. In this embodiment, the signal conditioning
circuitry as described above with respect to FIG. 14 is omitted for
simplicity. A system controller 1610 receives inputs from the
capacitance sensor conditioner 1606 via the multiplexor 1608, for
example, by activating each sensor in order and recording the
values. It may then compare measured values to pre-programmed
patterns and historical samples to determine lid position. The
capacitor touch sensors 1604 may be laid out in a physical pattern
similar to that previously described for the photodetectors, but
would be optimized for detecting changes in capacitance with lid
position. The sensors, and for that matter the whole electronic
system, would be encapsulated and insulated from the saline contact
lens environment. As the eyelid covers a sensor 1604, the change in
capacitance would be detected rather than the change in ambient
light previously described. FIG. 16B also illustrates the inclusion
of a power source 1614 in at least one embodiment.
[0136] It is important to note that ADC's and digital signal
processing circuitry may be utilized in accordance with the
capacitive touch sensors if needed as illustrated with respect to
the photosensors of FIG. 14B. In an alternative embodiment, the
capacitive touch sensors are any pressure sensor. In a further
embodiment, there is a combination of photosensors and pressure
sensors on the lens.
[0137] FIGS. 17A-17D illustrate an alternative embodiment where the
eyelid position sensor system is a sensor having a strip that
covers a plurality of vertical points along the contact lens 1702
that works in conjunction with circuit 1700. One example of a
sensor that may have a strip configuration is a capacitance sensor.
FIG. 17A illustrates an example where the strip 1708 is
substantially straight on the contact lens 1702. Although the strip
1708 is illustrated as being orientated parallel to a line
bisecting the contact lens 1702, it may have an angled orientation
relative to the bisecting line or have an arcuate shape. FIG. 17B
illustrates an example where the strip 1708a takes a serpentine
path along the contact lens 1702. In the embodiment illustrated in
FIG. 17C, the serpentine configuration of strip 1708b will increase
the change in capacitance detected by the circuit 1700 as the
eyelid approaches a closed state. The level of capacitance change
will translate to the amount of eyelid closure. Another example of
a sensor that may have a strip configuration is a piezoelectric
pressure transducer with a diaphragm and a base having a strip
configuration. As the eyelids close, additional pressure will be
applied by the eyelids against the piezoelectric pressure
transducer thus allowing the ability to determine the level of
eyelid closure. The continuous sensing along the vertical axis
provides an improved granularity over a plurality of sensors thus
providing improved measurement of the eyelid location. FIG. 17D
illustrates an electrical circuit that can be used in conjunction
with strip sensors 1708, 1708a, 1708b that includes a system
controller 1710, a data manager 1712 and a power source 1714. In a
further alternative embodiment, there are multiple strips present.
An advantage of an angled and/or serpentine strip configuration is
that lid position may still be detected even if the contact lens is
orientated incorrectly on the wearer's eye.
[0138] The activities of the digital signal processing block and
system controller (1416 and 1412 in FIG. 14B, respectively, system
controller 1610 in FIG. 16B, and system controller 1710 in FIG.
17D) depend on the available sensor inputs, the environment, and
user reactions. The inputs, reactions, and decision thresholds may
be determined from one or more of ophthalmic research,
pre-programming, training, and adaptive/learning algorithms. For
example, the general characteristics of eyelid movement may be
well-documented in literature, applicable to a broad population of
users, and pre-programmed into system controller. However, an
individual's deviations from the general expected response and/or
changes in blink frequency may be recorded in a training session or
part of an adaptive/learning algorithm which continues to refine
the response in operation of the electronic ophthalmic device. In
one embodiment, the user may train the device by activating a
handheld fob, which communicates with the device, when the user
desires near focus. A learning algorithm in the device may then
reference sensor inputs in memory before and after the fob signal
to refine internal decision algorithms. This training period could
last for one day, after which the device would operate autonomously
with only sensor inputs and not require the fob.
[0139] FIGS. 18A and 18B illustrate example eye movement sensor
systems 1800 for detecting movement of the eye during, for example,
sleep. Sensor 1802 detects the movement and/or position of the
pupil or, more generally, the eye. The sensor 1802 may be
implemented as a multi-axis accelerometer on a contact lens 1801.
With the contact lens 1801 being affixed to the eye and generally
moving with the eye, an accelerometer on the contact lens 1801 may
track eye movement. It is important to note that any suitable
device may be utilized as the sensor 1802, and more than a single
sensor 1802 may be utilized. The output of the sensor 1802 is
acquired, sampled, and conditioned by signal processor 1804. The
signal processor 1804 may include any number of devices including
an amplifier, a transimpedance amplifier, an analog-to-digital
converter, a filter, a digital signal processor, and related
circuitry to receive data from the sensor 1802 and generate output
in a suitable format for the remainder of the components of the
system 1800. The signal processor 1804 may be implemented utilizing
analog circuitry, digital circuitry, software, and/or a combination
thereof. In at least one embodiment, the signal processor 1804 and
the sensor 1802 are fabricated on the same integrated circuit die.
The sensor circuitry for acquisition and conditioning of an
accelerometer is different than the circuitry for a muscle activity
sensor or optical pupil tracker. The output of the signal processor
1804 in at least one embodiment is a sampled digital stream and may
include absolute or relative position, movement, detected gaze in
agreement with convergence, or other data. System controller 1806
receives input from the signal processor 1804 and uses this
information, in conjunction with other inputs, to determine whether
the wearer is asleep. System controller 1806 may both trigger the
activity of sensor 1802 and the signal processor 1804 while
receiving output from them. System controller 1806 uses input data
from the signal processor 1804 and/or transceiver 1810 to decide if
the wearer is lying down based on the orientation of the sensor
1802 based on orientation on an X, Y, and Z axes when no eye
movement is detected. If the axes are as illustrated in FIG. 18C,
then when the accelerometer detects stable acceleration in the X
axis in either direction or in the Z axis in either direction, then
the wearer's head has a horizontal orientation. When the
accelerometer detects stable acceleration in the Y axis in the
negative direction, then the wearer's head is vertical. When the
accelerometer detects stable acceleration in the Y and Z axes with
or without a stable acceleration in the X axis, then the wearer's
head is tilted forward.
[0140] FIGS. 18A and 18B illustrate an optional transceiver 1810
that receives and/or transmits communication through antenna 1812.
This communication may come from an adjacent contact lens,
spectacle lenses, or other devices. The transceiver 1810 may be
configured for two way communication with the system controller
1806. Transceiver 1810 may contain filtering, amplification,
detection, and processing circuitry as is common in transceivers.
The specific details of the transceiver 1810 are tailored for an
electronic or powered contact lens, for example, the communication
may be at the appropriate frequency, amplitude, and format for
reliable communication between eyes, low power consumption, and to
meet regulatory requirements. Transceiver 1810 and antenna 1812 may
work in the radio frequency (RF) bands, for example, 2.4 GHz, or
may use light for communication. Information received from
transceiver 1810 is input to the system controller 1806, for
example, information from an adjacent lens which indicates
orientation. The system controller 1806 may also transmit data
from, for example, the data manager 1808, to the transceiver 1810,
which then transmits data over the communication link via antenna
1812. In an alternative embodiment, the transceiver 1810 and the
antenna 1812 are replaced by an eyelid position sensor system to
provide communication via light waves and/or blinks as discussed
above.
[0141] The system controller 1806 may be implemented as a state
machine, on a field-programmable gate array, in a microcontroller,
or in any other suitable device. Power for the system 1800 and
components described herein is supplied by a power source 1814,
which may include a battery, energy harvester, or similar device as
is known to one of ordinary skill in the art. The power source 1814
may also be utilized to supply power to other devices on the
contact lens 1801.
[0142] The pupil position detection system 1800 in at least one
embodiment is incorporated and/or otherwise encapsulated and
insulated from the saline contact lens 1801 environment.
[0143] In at least one embodiment, the electronics and electronic
interconnections are made in the peripheral zone of a contact lens
rather than in the optic zone. In accordance with an alternative
embodiment, it is important to note that the positioning of the
electronics need not be limited to the peripheral zone of the
contact lens. All of the electronic components described herein may
be fabricated utilizing thin-film technology and/or transparent
materials. If these technologies are utilized, the electronic
components may be placed in any suitable location as long as they
are compatible with the optics.
[0144] In at least one embodiment as illustrated in FIG. 19, the
contact lens 1900 includes a sensor 1910 to detect at least one of
removal from a lens storage case and insertion of the contact lens
into the wearer's eye. In at least one embodiment, insertion of the
contact lens into the wearer's eye will activate sleep monitoring
by the system controller 1920. In a further embodiment, the
insertion will initiate an accumulator in the data manager 1922 to
run. Examples of sensors that would provide detection include, but
are not limited to, a pressure sensor, a reed switch, a salinity
sensor, a biosensor and a capacitive sensor. These sensors, in at
least one embodiment, work in conjunction with a light sensor to
detect the presence of light that occurs after removal of the
contact lens from the storage container. In a further embodiment to
the sensor embodiments, the sampling rate used to monitor the
sensor may be slowed after the detection of the event being
monitored to conserve power while allowing for the detection of
removal of the contact lens from the eye. In an alternative
embodiment to the prior embodiment, the sensor would be deactivated
upon detection of the contact lens being placed on the eye.
[0145] The pressure sensor may take a variety of forms. One example
is a rear-facing (or iris-facing) pressure sensor connected to the
system controller through an analog-to-digital convertor. The
rear-facing pressure sensor in at least one embodiment is partially
encapsulated in the contact lens while the analog-to-digital
convertor is completely encapsulated in the contact lens and
included as part of any circuit board present in the contact lens.
The system controller resets the accumulator upon receiving a
signal from the pressure sensor in excess of an insertion threshold
indicating that data collection should begin by the system
controller. The system controller sends a signal to the data
manager to store the current accumulator value when the signal from
the pressure sensor then falls below the insertion threshold
indicating that the contact lens has been removed and further data
collection is unnecessary. The system controller samples the
pressure sensor at a predetermined schedule only when the system
controller detects the eyelid is open. Another example of a
pressure sensor is a pressure sensor that will detect the removal
of pressure from the saline present in the storage container and
would provide a signal to activate the other functionality of the
contact lens. A further example of a pressure sensor is a surface
acoustic wave resonator with interdigital transducer (IDT). A still
further example is a binary contact pressure sensor that either
detects pressure or no pressure, but not the level of pressure.
[0146] One example of a reed switch completes a circuit in the
contact lens that provides power to the rest of the circuit
elements by application of pressure from the wearer's eye upon
insertion of the contact lens or the removal of pressure when the
contact lens is removed from the storage container for use. Upon
the respective event occurring, the reed switch would close and
complete the circuit to provide an electrical connection between
the system controller and the power supply. Another example of a
reed switch use in the system is to provide a binary output upon
the switch being activated with the binary output providing an
indication of the switch being closed (or open depending on the
orientation of the switch) as opposed to completing a circuit.
[0147] A salinity sensor or biosensor in at least one embodiment
would detect salinity or another chemical present in tear fluid.
Examples of the substances that could be monitored include, but are
not limited to, a pathogen, a biomarker, an active agent, and a
chemical. One example of a biosensor is a resistance tab, in
electrical communication with system controller, that is capable of
binding with the substance being monitored resulting in an
increasing resistance as the amount of substance present increases.
Another example is a reactive tube(s) that contains a substance,
material, or mixture that may react with a specific molecule where
a reaction will be indicative of the presence of a chemical being
monitored. Yet another example is a biosensor in which a surface is
functionalized to have affinity for a certain substance, and an
electrical property of the sensor, for example capacitance or
voltage, varies in response to the presence of the substance to
which the sensor is functionalized. In at least one embodiment,
where a chemical being monitored relates to a concentration of some
substance in the tear fluid, the reaction may occur directly with
that substance or may occur with a separate substance that may
indicate concentration of the monitored substance. In other
examples, because other electroactive biological components may
affect the conductivity within a particular tube, the tube may be
lined with or include a selective barrier to minimize interference
with the other substances than the substance being monitored.
Alternatively to a tube having an increasing conductivity in
response to the presence of the monitored substance, the tube may
instead have an increasing resistivity in the presence of the
monitored substance. A further example will have the hollow tube
include material that is selectively permeable or attractive to a
specific substance or chemical. Under any of these examples, it may
be possible to provide a graduated indication of the level of the
substance beyond a binary output.
[0148] The capacitive sensor may be rear facing or forward facing.
In at least one embodiment, the sensor would be a rear-facing
sensor to allow for contact by the wearer's eye. In a further
embodiment, once a contact causes a change in capacitance above an
insertion threshold indicating that the contact lens has been
inserted, the sensor is deactivated or has its sampling rate
decreased. If, however, the sensor was forward facing, then contact
by one of the eyelids that would change the capacitance above the
insertion threshold would confirm insertion of the contact lens. In
a further embodiment, the forward-facing capacitive sensor would
also be used for detection of the position of the eyelids.
[0149] In complex systems which may include multiple sensors, such
as powered ophthalmic lenses having a number of electronic
components, it is preferable to reduce the potential for initiating
false actions or false positive triggering of a sleep
determination. In accordance with another alternative embodiment,
this embodiment is directed to a decision making process and/or
voting scheme which utilizes input from multiple sensors to
substantially reduce the possibility of changing the state of the
powered ophthalmic lens based upon inaccurate, incomplete or
erroneous information, changing physiologic conditions, as well as
noise and/or interference from internal and external sources. For
example, in sleep detection, the control system should not
determine sleep onset based upon a random blinking pattern due to
eye irritation or the like. However, with input from a single
sensor or erroneous information from the single sensor or other
sensors, incorrect decisions may be made by the system controller.
For example, without knowing the pressure applied to the ophthalmic
lens, simply closing the eye lids might trigger a sleep
determination despite the wearer rubbing their eyes and applying a
pressure greater than lid pressure on a pressure sensor(s). In a
powered ophthalmic lens having an eyelid position sensor, eyelid
movement may also be utilized as a trigger for making a sleep
determination. For example, when an individual gazes down to focus
on a near distance object, the eyelids tend to droop and thus it
may be utilized to change the state of the ophthalmic lens. Once
again, if only a single input is utilized, a false action may take
place due to the fact that the person is sleepy and their eyelids
drooped. All of these sensors may be utilized as triggers for
action to be implemented by various systems incorporated into an
electronic or powered ophthalmic lens, and all of them
independently or in limited combination are potentially subject to
error. In addition to the sensors already mentioned which are
intended to detect certain aspects directly related to determining
sleep onset, other sensors may be used to improve state-change
sensors by monitoring ambient conditions, noise, and interference.
For example, ambient light may be monitored to improve the accuracy
of blink detection, lid position, and pupil diameter sensors. Such
sensors may be utilized to augment other sensors, for example, by
subtracting common mode noise and interference. Sensor inputs may
be used to record history readings which are then considered by a
complex decision algorithm, for example, one which considers both
accelerometer inputs and eye muscle contraction to determine pupil
position. Utilizing the voting scheme in accordance with at least
one embodiment may reduce the likelihood of error in determining
whether the wearer has fallen asleep and may also allow more
precise measurements. In other words, for any given determination
to be made, there are sensors that may be utilized to check
corroborating evidence or to augment input for a given
determination by a primary sensor. It is also important to note
that the sensed data, in addition to or in alternate use, may
simply be utilized as part of a collection process rather than as a
triggering event. For example, the sensed data may be collected,
logged and utilized in treating medical conditions. In other words,
it should also be appreciated that a device utilizing such a sensor
may not change state in a manner visible to the user; rather the
device may simply log data.
[0150] Referring now to FIG. 20, there is illustrated a generic
system in which sensors 2002, 2004, 2006 and 2008 are used to
determine if sleep onset and/or an event during sleep. The sensors
2002, 2004, 2006 and 2008 may include any number of potential
inputs including blink action, lid position, pupil position,
contact lens orientation, external lens pressure, and the like. The
number and type of sensors is determined by the application and
user. Each sensor 2002, 2004, 2006 and 2008 may have its own signal
conditioning contained within the sensor block, a dedicated block,
or within the system controller 2010. The system controller 2010
accepts inputs from each sensor 2002, 2004, 2006 and 2008. It then
performs routines to process and compare the input data. Based on
these inputs, the system controller 2010 determines if the data
manager 2012 should record any readings. For example, the
combination of eyelid droop, low ambient light, and vertical lens
orientation may trigger the system controller 2010 to determine the
wearer is drowsy and to signal the data manager 2012 to increase
the sampling rate of at least one sensor system being used to make
the sleep determination. Likewise, the combination of eyelid
closure, vertical orientation for the wearer, and external eyelid
pressure may trigger the system controller 2010 to determine no
sleep onset and continue regular operation. The combination of lid
closure, horizontal orientation for the wearer may trigger the
system controller 2010 to determine sleep onset and to signal the
alert mechanism to record data as the sleep is likely intentional
sleep given the wearer's orientation. Inputs from various sensors
may also be utilized to alter the configuration of the system
controller to improve decision making performance, for example, if
ambient light decreases, the controller may increase the gain of a
photosensor. The system controller may also turn sensors on and/or
off, increase and/or decrease sampling rates, and make other
changes to the system to optimize performance.
[0151] FIG. 21 illustrates a method by which a system controller,
for example, system controller 2010 illustrated in FIG. 20,
operates to sample sensors and determine sleep status. The first
step is to sample the sensors, 2102. This may require triggering
other elements to activate, warm-up, calibrate, take readings,
condition, and output data. The system controller may also provide
configuration information to each sensor based on programmed values
and current data, for example, the gain of a photosensor amplifier
based on the history of incident light, or these settings may be
determined by other elements in the system. Then the method
performs filtering and additional conditioning, 2104, for example,
digital as opposed to analog filtering, along with a comparison to
baseline or reference results. One purpose of this step is to
properly condition the input data for the next step so that an
accurate, repeatable decision may be made. Then the results are
determined from each sensor, 2106, for example, the lid position
and emitter-detector response. This determination may involve
comparison to a pre-programmed or variable threshold, comparison to
a specific pattern, or any other determination. The results are
aggregated from the previous step, weighting the results and making
a decision, 2108. This step in at least one embodiment may involve
per-user training and preferences, ensuring all sensors have been
sampled before deciding, and various weights applied to the results
of each sensor. In at least one embodiment, a decision is made that
is predictable and repeatable in the presence of real-world noise
and interference. If a decision is made regarding sleep status as
described above, then recording data, 2110. Regardless of the
decision regarding sleep status, returning the system to sampling
so another set of measurements and determination may take place,
2112. The total time required to execute the process in FIG. 21 in
at least one embodiment is short enough such that the system is
responsive to user inputs similar to how individuals naturally
interact with their environments. For example, if utilized to
activate a variable-power focus lens, the system should change
focus state within approximately one (1) second, similar to that of
the natural accommodation system.
[0152] It should be appreciated that each sensor input may vary for
reasons other than sleep. For example, the eye impedance may vary
over time due to changes in body hydration, salt intake, level of
exertion, or other means. Likewise, pupil diameter may vary due to
changes in ambient light levels. Thus, it should be apparent that
combining multiple sensor inputs reduces the chances of false
positive triggering by requiring more than one input to correlate
with a desired change in focal length or by using certain sensor
inputs to augment other sensors.
[0153] It should also be apparent that the thresholds for each
sensor and the combination of sensors used to determine sleep
and/or selection of data to log during sleep depends on many
variables such as safety, response time, and user preferences. The
specific programming of the voting scheme may be based on clinical
observations of a number of subjects and individual programming
tailored to a specific user. Parameters in the voting scheme may be
dependent on sensor inputs, for example, the threshold and gain
setting for blink detection may vary with ambient light.
[0154] In an alternative embodiment, the system further includes a
memory preservation controller that is in electrical communication
with the power source and the system controller. In at least one
embodiment, the memory preservation controller is an example of the
resource management system 140 discussed in connection with FIG.
1A. The memory preservation controller, at a predetermined
frequency, tests the power source to determine the level of energy
that remains. When the remaining energy falls below a predetermined
energy threshold, the memory preservation controller sends an
instruction to the system controller to no longer sample the sensor
system and to send a signal causing the recording by the data
manager of the current time and/or accumulator value. The power
then is provided to maintain the data in memory and/or data storage
present on the contact lens. In a further embodiment when the power
supply finds the available energy level below a low-energy
threshold, the system will perform at least one of the following:
reducing the sampling rate for at least one of the accelerometer
and the transducer, reducing the sampling rate of at least one
sensor, terminating further sampling of at least one of the
accelerometer and the transducer, terminating further monitoring of
the power supply, storing a time stamp representing low-energy
based on the current value in the accumulator, removing power from
at least one of the accelerometer and the transducer, sampling the
lid closure at a second lid sampling rate that is slower than the
first sampling rate, powering a memory where the readings are
stored, or any combination of these. Based on this disclosure one
of ordinary skill in the art should appreciate that a particular
implementation may have just one of these options available and
that this is contemplated to be covered by the at least one of
language.
[0155] The predetermined energy threshold is based on an estimate
of the power required to maintain a power supply to any memory or
data storage. In a further embodiment, the threshold is adjusted
based on the current run time of the lens while still facilitating
an estimated period of power for the memory and/or data storage.
One example of how to adjust the threshold over time is to
decrement a register for each passing of a predetermined time as
measured by sampling periods in the contact lens.
[0156] In a further embodiment, the energy level test is done in
conjunction with the sampling of the sensor system(s) to compare
the energy level of the power source to the threshold under maximum
load of the lens as occurs when a sensor system(s) is providing a
reading(s). If the energy level for the power source is below a
threshold, then there is a high likelihood that an upcoming sensor
sampling, prior to the next energy level test, will drain the power
source such that the sensor system(s) will provide an incorrect
reading because of insufficient power being available and/or stored
data will become corrupted thus leading to a data set that is
unreliable.
[0157] In a modified alternative embodiment, the memory
preservation controller places an artificial load on the power
source during periods of non-sampling of the sensor(s). Example
sampling time periods include but are not limited to 1 minute, 2
minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, and 30
minutes. Other examples of testing the power source include, but
are not limited to, obtaining a loaded voltage, introducing a
special test waveform to pulse current out the battery and
measuring voltage drop with the comparison of the results being
compared to a predetermined threshold that in a further embodiment
can be adjusted downward in view of expected remaining run
time.
[0158] In a further alternative embodiment, the memory preservation
controller monitors the data manager to determine remaining space.
When the remaining space in memory of the data manager is less than
a free space threshold, the memory preservation controller sends a
signal to the system controller to do at least one of the
following: terminate sampling the sensor system(s) to avoid
creating additional data for storage, send a signal to the data
storage to set a flag of memory full and to shift the currently
stored data to provide additional space using a first in first out
approach, and remove power from the system controller and the
sensor system(s) leaving power being supplied to just the data
storage. Other examples include storing a time stamp representing
low memory based on the current value in the accumulator, reducing
the sampling rate for at least one of the accelerometer and the
transducer, terminating further sampling of at least one of the
accelerometer and the transducer, storing future readings from at
least one of the accelerometer and the transducer over the earliest
stored readings in the memory, deleting the stored sensor readings
associated with the lowest accumulator reading and shifting the
remaining stored sensor and accumulator readings in the memory, and
any combination of these examples.
[0159] In a further embodiment to the above embodiments, the memory
preservation controller and/or the resource management system is
part of the system controller.
[0160] In at least one embodiment, the system further includes a
storage box. The storage box in at least one embodiment includes a
housing with a base and a cover that are connected along one edge
to facilitate opening the cover relative to the base to allow for
deposit of the contact lens into a cavity in the housing. In
alternative embodiments, the storage box may include disinfecting,
monitoring, reordering and external connectivity functionality. The
disinfecting functionality would allow for the lenses to be used
over an extended period of time by the wearer.
[0161] FIG. 22 illustrates an example storage box having a housing
2200, a communication system, a memory, a clock, an electrical
communication connector 2202, and a power source 2206. In an
alternative embodiment, the storage box includes a radiation
disinfecting base unit 2204 contained within a housing such as the
previously described housing and cover. The electrical
communication connector 2202 may include a universal serial bus
(USB) connector or other type of connector. The connector may
include a terminal for transferring one or both of data and
electrical power. In some embodiments, the electrical communication
connector 2202 provides power to operate the radiation disinfecting
base unit 2204. Some embodiments may also include one or more
batteries 2206 or other power storage device. In some embodiments,
the batteries 2206 include one or more lithium-ion batteries or
other rechargeable device. The power storage devices may receive a
charging electrical current via the electrical communication
connector 2202. In at least one battery embodiment, the radiation
disinfecting base unit 2204 is operational via stored power in the
batteries 2206.
[0162] In at least one embodiment, the communication system
includes an antenna such as a radio-frequency identification (RFID)
antenna for interacting with inserted lenses and a controller
electrically communicating with said antenna. In at least one
embodiment, the controller is in electrical communication with at
least one memory, which in at least one embodiment is flash memory
like that used in a memory stick. Examples of the interaction
include wireless recharging of the power source on one or both
lenses, transferring data stored on the lens(es) to memory in (or
in communication with) the storage box, and transferring templates
and masks based on wearer-specific characteristics from the storage
box to at least one lens. In an alternative embodiment, the antenna
is used to communicate with an external device such as a computer
or smart phone.
[0163] In at least one embodiment, the controller is configured to
translate and/or format the data received from the at least one
lens to change the time stamp information into actual times based
on the current accumulator reading at the time of data transfer as
correlated to the current time on the storage box. In an
alternative embodiment, the storage box sends a signal to the lens
to reset the accumulator to zero and the processor records in
memory the time that the accumulator was reset to zero. After
reinsertion of the lens into the storage box, the processor notes
the current time and determines the number of sampling cycles. In
the embodiments where the sampling cycles are of different lengths
depending on what is being sampled and/or operational state of the
lens(es) since removal of the lens(es), the storage box normalizes
the sample periods over the time difference between removal of the
lens(es) from the storage box and return of the lens(es) to the
storage box as measured by the storage box.
[0164] In some embodiments, the electrical communication connector
2102 may include a simple source of AC or DC current. In such
embodiments, the power source 2106 may be omitted as power is
provided through the electrical communication connector 2102.
[0165] An intraocular lens or IOL is a lens that is implanted in
the eye and replaces the crystalline lens. It may be utilized for
individuals with cataracts or simply to treat various refractive
errors. An IOL typically comprises a small plastic lens with
plastic side struts called haptics to hold the lens in position
within the capsular bag in the eye. Any of the electronics and/or
components described herein may be incorporated into IOLs in a
manner similar to that of contact lenses.
[0166] FIG. 23 illustrates a method for monitoring sleep with a
powered ophthalmic lens. As discussed above, there are a variety of
ways to activate the powered ophthalmic lens, 2302. In at least one
embodiment, in response to activation of the powered ophthalmic
lens or alternatively a sleep monitoring operation state, an
accumulator is initiated on the lens to track a passage of time,
2304. The system controller monitors the eyelid position sensor
system for whether the eyelid(s) has closed at a first sampling
rate, 2306. When the system controller detects the eyelid has
closed, an eye movement sensor system (such as an accelerometer
and/or a transducer) is sampled, 2308. The system controller
determines whether the reading from the eye movement sensor system
exceeds a threshold, 2310. In at least one embodiment, when the
threshold is exceeded, then this is indicative of REM sleep. When
the threshold is exceeded, the system controller retrieves a
reading from the accumulator, 2312, and stores the accumulator
reading with the eye movement sensor reading, 2314. The system
controller monitors the eye movement sensor to determine when the
reading is below the threshold to indicate in at least one
embodiment the end of REM sleep prior to returning to sampling
eyelid closure readings, 2316.
[0167] In an alternative embodiment, the sampling of and storing of
data from the eyelid position sensor system and the eye movement
sensor system occurs with or without an accumulator begins once the
ophthalmic lens is activated for data collection. The data is
transferred to an external device (e.g., external device 1390 in
FIG. 13B) for analysis and/or review during the data collection or
after data collection has begun. In a further embodiment, the
sampling and storing continue until a terminate signal is received
indicating the end of the data collection and/or a resource
management system determines there are insufficient resources
available. In a further alternative embodiment, instead of storing
the data, the data is transmitted to the external device
[0168] In a further embodiment, a level of light is measured with a
photosensor present on the contact lens. The light level reading is
stored as an initial light level along with a reading from the
accumulator by, for example, the data manager. The system
controller monitors the photosensor to determine when a change in
light level occurs and storing the current reading from the
accumulator with the light level reading. This allows for the level
of ambient light to be monitored while the eyelids are open to
allow for analysis of the sleep pattern. In a further embodiment,
the system controller compares the accumulator reading to a
duration threshold. When the accumulator exceeds the duration
threshold, the system controller samples the photosensor to
determine if the current light level approximates the initial light
level reading such that when the initial light level is reached the
sleep monitoring is terminated. In at least one embodiment this
allows for reduced sampling and monitoring of the current light
level until an anticipated sleep time has passed.
[0169] In at least one embodiment, the sampling rates of the eyelid
position sensor and/or the eye position sensor is changed to a
second sampling rate (e.g., a second lid sampling rate and a second
motion sampling rate). In at least one embodiment, the second
sampling rates are slower while in another embodiment the second
sampling rates are faster.
[0170] In at least one embodiment, the contact lens performs the
method in conjunction with an external device that in at least one
embodiment provides storage and/or processing power. The contact
lens when storing a reading also transmits the reading to the
external device for storage. In an alternative embodiment, the
contact lens does not store the reading and relies on the external
device to store the reading. In at least one embodiment, the
external device stores the reading along with a time stamp based on
the current time on the external device, while in an alternative
embodiment the external device adjusts the time stamp to take into
account transmission time between the contact lens and the external
device. In at least one embodiment, the external device samples
light levels with, for example, a camera or other CCD, to store the
light level with a time stamp in memory on the external device. In
at least one embodiment as discussed previously, the external
device may provide an interface that allows for user input
regarding initiation of a sleep study and a termination of a sleep
study.
[0171] In an alternative method embodiment illustrated in FIG. 24,
the powered ophthalmic lens is activated, 2402, although in at
least one embodiment this step is omitted. The system controller
and/or the data manager initiates an accumulator to track a passage
of time, 2404. The system controller samples an eye position sensor
such as an accelerometer or a transducer, 2406, where in at least
one embodiment this sampling occurs at least once. The reading
received from the eye position sensor is compared to a threshold by
the system controller, 2408, such that when the threshold is
exceeded the system controller and/or data manager: retrieves a
reading from the accumulator, 2410; stores the accumulator reading
and the eye position sensor reading, 2412; and determines whether a
later sampled reading is below the threshold, 2414, such that when
the reading is below the threshold storing an indication of a REM
end, 2416. In at least one embodiment, the thresholds are different
values while in another embodiment the thresholds are the same
threshold with the thresholds being a first threshold and a second
threshold. In a variety of alternative embodiments, the embodiments
discussed in addition to the method illustrated in FIG. 23 work in
conjunction with the method illustrated in FIG. 24.
[0172] In an alternative method embodiment illustrated in FIG. 25,
the lens is activated, 2502, although in at least one embodiment
this step is omitted. The system controller and/or the data manager
initiates an accumulator to track a passage of time, 2504. The
system controller samples an eye position sensor such as an
accelerometer or a transducer, 2506, where in at least one
embodiment this sampling occurs at least once. The system
controller and/or data manager: retrieves a reading from the
accumulator, 2508; then stores the accumulator reading and the eye
position sensor reading, 2510. In at least one embodiment, the
sampling, retrieving and storing steps are repeated until
deactivation or termination of the method occurs with examples
including the various approaches discussed previously.
[0173] Although shown and described in what is believed to be the
most practical embodiments, it is apparent that departures from
specific designs and methods described and shown will suggest
themselves to those skilled in the art and may be used without
departing from the spirit and scope of the invention. The present
invention is not restricted to the particular constructions
described and illustrated, but should be constructed to cohere with
all modifications that may fall within the scope of the appended
claims.
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