U.S. patent application number 13/212814 was filed with the patent office on 2012-04-19 for polarization-sensitive visual prosthesis.
This patent application is currently assigned to Massachusetts Eye & Ear Infirmary, a Massachusetts corporation. Invention is credited to Dimitri T. Azar.
Application Number | 20120092613 13/212814 |
Document ID | / |
Family ID | 36207123 |
Filed Date | 2012-04-19 |
United States Patent
Application |
20120092613 |
Kind Code |
A1 |
Azar; Dimitri T. |
April 19, 2012 |
POLARIZATION-SENSITIVE VISUAL PROSTHESIS
Abstract
A vision prosthesis includes a first detector disposed to detect
a polarization state of light reflected from a retina, and a
controller in communication with the first detector. The controller
is configured to receive, from the detector, a measurement signal
indicative of the polarization state. In response thereto, the
controller generates a control signal for causing a change to an
optical property of an optical system in optical communication with
the retina.
Inventors: |
Azar; Dimitri T.; (Chicago,
IL) |
Assignee: |
Massachusetts Eye & Ear
Infirmary, a Massachusetts corporation
|
Family ID: |
36207123 |
Appl. No.: |
13/212814 |
Filed: |
August 18, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11577780 |
Nov 21, 2008 |
|
|
|
PCT/US2005/037783 |
Oct 20, 2005 |
|
|
|
13212814 |
|
|
|
|
10971434 |
Oct 22, 2004 |
7141065 |
|
|
11577780 |
|
|
|
|
Current U.S.
Class: |
351/159.03 ;
351/159.39; 623/6.22 |
Current CPC
Class: |
A61F 2/14 20130101; A61F
2/1624 20130101; A61F 2/16 20130101; A61F 2250/0002 20130101; A61F
9/00 20130101 |
Class at
Publication: |
351/159.03 ;
623/6.22; 351/159.39 |
International
Class: |
G02C 7/08 20060101
G02C007/08; A61F 2/16 20060101 A61F002/16; A61F 2/14 20060101
A61F002/14 |
Claims
1. A manufacture comprising a computer-readable medium having
encoded thereon software for controlling an optical property of an
optical system, the software including instructions for causing a
processor to change an optical property of the optical system in
response to a detection of a polarization state of light reflected
from a retina in an eye.
2. The manufacture of claim 1, wherein the software comprises
instructions for generating a control signal at least in part on
the basis of a comparison between polarized light reflected from a
foveal region of the retina and polarized light reflected from a
non-foveal region on the retina.
3. The manufacture of claim 1, wherein the software comprises
instructions for generating a control signal on the basis of a
comparison between the polarization state as detected by a first
detector and a polarization state associated with light reflected
from a fovea of the retina.
4. The manufacture of claim 1, wherein the software comprises
instructions for causing a change to a focal length of the optical
system.
5. The manufacture of claim 1, wherein the software comprises
instructions for causing a change to an optical property of a lens
of an eye.
6. The manufacture of claim 1, wherein the software comprises
instructions for causing a change to an optical property of an
intra-ocular lens.
7. The manufacture of claim 1, wherein the software comprises
instructions for causing a change to an optical property of a
contact lens.
8. The manufacture of claim 1, wherein the software comprises
instructions for causing a change to an optical property of an
eyeglass lens.
9. An apparatus for controlling an optical property of an optical
system, the apparatus comprising a controller configured to execute
instructions for causing an optical property of an optical system
to change in response to detecting a polarization state of light
reflected from a retina; and a storage device in data communication
with the controller, the storage device having stored thereon
instructions that, when executed by the controller, cause the
controller to output, at least in part on the basis of the detected
polarization state of light reflected from the retina, a control
signal that, when provided to an optical system, causes a change to
an optical property of the optical system.
10. The apparatus of claim 9, wherein the controller is configured
to generate a control signal at least in part on the basis of a
comparison between polarized light reflected from a foveal region
of the retina and polarized light reflected from a non-foveal
region on the retina.
11. The apparatus of claim 9, wherein the controller is configured
to generate a control signal on the basis of a comparison between
the polarization state as detected by a first detector and a
polarization state associated with light reflected from a fovea of
the retina.
12. The apparatus of claim 9, wherein the controller is configured
to generate a control signal to cause a change to a focal length of
the optical system.
13. The apparatus of claim 9, wherein the controller is configured
to cause a change to an optical property of a lens of an eye.
14. The apparatus of claim 9, wherein the controller is configured
to be in electrical communication with an intra-ocular lens for
causing a change to an optical property thereof.
15. The apparatus of claim 9, wherein the controller is configured
to be in electrical communication with a contact lens for causing a
change to an optical property thereof.
16. The apparatus of claim 9, wherein the controller is configured
to be in electrical communication with an eyeglass lens for causing
a change to an optical property thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation (and claims the benefit
of priority under 35 USC 120) of U.S. application Ser. No.
11/577,780, filed Nov. 21, 2008, which is a national stage entry of
PCT/US2005/037783 filed Oct. 20, 2005, which claims the benefit of
the priority date of U.S. application Ser. No. 10/971,434 filed
Oct. 22, 2004, which has issued as U.S. Pat. No. 7,141,065. These
applications are herein incorporated by reference in their
entireties.
RELATED APPLICATIONS
[0002] This application is a divisional of U.S. patent application
Ser. No. 10/971,434, filed on Oct. 22, 2004, the entire contents of
which are hereby incorporated by reference.
FIELD OF INVENTION
[0003] This invention relates to a vision prosthesis, and in
particular, to dynamic control of optical characteristics of a
vision prosthesis.
BACKGROUND
[0004] In the course of daily life, one typically regards objects
located at different distances from the eye. To selectively focus
on such objects, the focal length of the eye's lens must change. In
a healthy eye, this is achieved through the contraction of a
ciliary muscle that is mechanically coupled to the lens. To the
extent that the ciliary muscle contracts, it deforms the lens. This
deformation changes the focal length of the lens. By selectively
deforming the lens in this manner, it becomes possible to focus on
objects that are at different distances from the eye. This process
of selectively focusing on objects at different distances is
referred to as "accommodation".
[0005] As a person ages, the lens loses plasticity. As a result, it
becomes increasingly difficult to deform the lens sufficiently to
focus on objects at different distances. To compensate for this
loss of function, it is necessary to provide different optical
corrections for focusing on objects at different distances.
[0006] One approach to applying different optical corrections is to
carry different pairs of glasses and to swap glasses as the need
arises. For example, one might carry reading glasses for reading
and a separate pair of distance glasses for driving. This is
inconvenient both because of the need to carry more than one pair
of glasses and because of the need to swap glasses frequently.
[0007] Bifocal lenses assist accommodation by integrating two
different optical corrections onto the same lens. The lower part of
the lens is ground to provide a correction suitable for reading or
other close-up work while the remainder of the lens is ground to
provide a correction for distance vision. To regard an object, a
wearer of a bifocal lens need only maneuver the head so that rays
extending between the object-of-regard and the pupil pass through
that portion of the bifocal lens having an optical correction
appropriate for the range to that object.
[0008] The concept of a bifocal lens, in which different optical
corrections are integrated into the same lens, has been generalized
to include trifocal lenses, in which three different optical
corrections are integrated into the same lens, and continuous
gradient lenses in which a continuum of optical corrections are
integrated into the same lens. However, just as in the case of
bifocal lenses, optical correction for different ranges of distance
using these multifocal lenses relies extensively on relative motion
between the pupil and the lens.
[0009] Once a lens is implanted in the eye, the lens and the pupil
move together as a unit. Thus, no matter how the patient's head is
tilted, rays extending between the object-of-regard and the pupil
cannot be made to pass through a selected portion of the implanted
lens. As a result, multifocal lenses are generally unsuitable for
intraocular implantation because once the lens is implanted into
the eye, there can be no longer be relative motion between the lens
and the pupil.
[0010] A lens suitable for intraocular implantation is therefore
generally restricted to being a single focus lens. Such a lens can
provide optical correction for only a single range of distances. A
patient who has had such a lens implanted into the eye must
therefore continue to wear glasses to provide optical corrections
for those distances that are not accommodated by the intraocular
lens.
SUMMARY
[0011] A vision prosthesis according to the invention includes an
auto-focus mechanism that relies on the difference between the
birefringent properties of the fovea, and the birefringent
properties of portions of the retina surrounding the fovea,
referred to herein as the "circumfovea." By illuminating the retina
with polarized light, and measuring the polarization state of light
reflected from the retina, it is possible to estimate how much of
the reflected light was reflected by the fovea and how much was
reflected by the circumfovea. On the basis of this estimate, a
controller causes a change in an optical property of an optical
system. This, in turn cause a desired change in the estimate.
[0012] In one aspect, the vision prosthesis includes a first
detector disposed to detect a polarization state of light reflected
from a retina; and a controller in communication with the first
detector. The controller is configured to receive, from the
detector, a measurement signal indicative of the polarization
state, In response, the controller generates a control signal for
causing a change to an optical property of an optical system in
optical communication with the retina.
[0013] Some embodiments also include a first polarizer in optical
communication with the retina. The first polarizer blocks passage
of light having a first polarization state. The first polarizer can
include, for example, a first polarizing region of a lens in the
optical element.
[0014] Embodiments that include a first polarizer optionally
include a second detector disposed to detect light passing through
the first polarizer. The second detector is configured to provide,
to the controller, a signal representative of light passing through
the first polarizer.
[0015] Embodiments that include a first polarizer can also include
a second polarizer in optical communication with the retina. The
second polarizer blocks passage of light having a second
polarization state orthogonal to the first polarization state.
[0016] In some embodiments, the first detector in configured to be
implanted in a cornea.
[0017] Other embodiments of the vision prosthesis also include
those in which the optical system includes an intra-ocular lens, a
contact lens, an eyeglass lens, or a natural lens of the eye.
[0018] The controller can be configured to generate a control
signal at least in part on the basis of a comparison between
polarized light reflect from a foveal region of the retina and
polarized light reflected from elsewhere on the retina. However,
the controller can also be one that is configured to generate a
control signal on the basis of a comparison between the
polarization state as detected by the first detector and a
polarization state associated with light reflected from a fovea of
the retina. Or, the controller can be one that is configured to
generate a control signal to cause a change to a focal length of
the optical system.
[0019] In another aspect, the invention includes a vision
prosthesis having a controller configured to cause an optical
property of an optical element to change in response to a signal
indicative of a polarization state of light reflected from a
retina.
[0020] Another aspect of the invention includes a method for
controlling a vision prosthesis by detecting a polarization state
of light reflected from a retina and receiving a measurement signal
indicative of the polarization state. In response to the signal, a
control signal causes a change to an optical property of an optical
system in optical communication with the retina.
[0021] In some practices, generating a control signal includes
comparing polarized light reflected from a foveal region of the
retina and polarized light reflected from elsewhere on the retina.
The control signal is generated at least in part on the basis of
the comparison.
[0022] In other practices, generating a control signal includes
generating a control signal at least in part on the basis of a
polarization state associated with light reflected from a fovea of
the retina.
[0023] The method can also include causing a change to a focal
length of the optical system in response to the control signal.
[0024] Unless otherwise defined, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs. Although
methods and materials similar or equivalent to those described
herein can be used in the practice or testing of the present
invention, suitable methods and materials are described below. All
publications, patent applications, patents, and other references
mentioned herein are incorporated by reference in their entirety.
In case of conflict, the present specification, including
definitions, will control. In addition, the materials, methods, and
examples are illustrative only and not intended to be limiting.
[0025] Other features and advantages of the invention will be
apparent from the following detailed description, and from the
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 shows a lens focusing light on the fovea;
[0027] FIG. 2 shows a lens focusing light anterior to the
fovea;
[0028] FIG. 3 shows an embodiment of a vision prosthesis with two
detectors and one polarizing region;
[0029] FIG. 4 illustrates resolution of polarization vectors;
[0030] FIG. 5 shows an embodiment of a vision prosthesis with two
polarizing regions and one detector; and
[0031] FIG. 6 is an embodiment in which polarization is provided by
the cornea.
DETAILED DESCRIPTION
[0032] FIG. 1 shows polarized light entering a lens 10 and being
focused onto a retina 12, and in particular, onto the fovea 14 of
the retina. The polarized light is characterized by an incident
polarization state P.sub.I. In the process of being reflected by
the fovea 14, the incident light has its polarization state
changed. The foveally-reflected light thus has a reflected
polarization state, P.sub.F, that differs from the incident
polarization state, P.sub.I. The extent of this difference
corresponds to the birefringent properties of the fovea 14.
[0033] FIG. 2 shows polarized light entering a lens 10 that fails
to focus onto the fovea 14. In this particular example, the lens 10
brings light to a focus anterior to the retina 12. However, the
same principle is at work when the lens 10 brings light to a focus
posterior to the retina 12. In both cases, polarized light
illuminates both the fovea 14 and the circumfovea 16. The reflected
light is therefore a combination of foveally-reflected light, which
is characterized by a first polarization state P.sub.F, and
circumfoveally-reflected light, which is characterized by a second
polarization state P.sub.CF. As a result, the reflected light
acquires a net polarization state that depends in part on the
relative contributions of the foveal reflection and the
circumfoveal reflection.
[0034] The difference between the polarization state of the
reflected light in FIG. 1 and the polarization state of reflected
light in FIG. 2 provides a way to determine whether the lens 10 is
correctly focusing light on the fovea 14. When the lens 10 is in
focus, the reflection is dominated by foveally-reflected light.
Thus, to the extent light reflected from the retina 12 has a
polarization state consistent with foveally reflected light, the
lens 10 is in focus.
[0035] In the block diagram of FIG. 3, a vision prosthesis 17
includes an actuator 18 for changing an optical property of an
optical system 20. The optical system 20 can include the natural
crystalline lens of the eye, an intraocular lens implanted in the
eye, a contact lens, or an eyeglass lens. Exemplary lenses include
the nematic crystal lenses described in U.S. Pat. No. 6,638,304,
and the deformable and/or translatable lenses described in U.S.
application Ser. 10/895,504, filed on Jul. 21, 2004. The contents
of both are incorporate herein by reference.
[0036] A variety of actuators can be used in the vision prosthesis
16. These include the electrodes described in U.S. Pat. No.
6,638,304 and the artificial muscle actuators described in U.S.
application Ser. No. 10/895,504, filed on Jul. 21, 2004.
[0037] In the vision prosthesis 17 shown in FIG. 3, the lens 20 has
a polarizing region 22 that allows passage only of light having a
first polarization state. A first detector 24 is disposed to sample
light exiting the polarizing region 22. This first detector 24
provides, to a controller 26, a first signal indicative of the
polarization state of that incoming light. A second detector 28 is
disposed to sample light reflected from the retina 12. This second
detector 28, provides to the controller 26, a second signal
indicative of the polarization state of the reflected light. The
first and second signals together provide an indication of the
extent to which reflection from the retina 12 changes the
polarization state of the polarized light incident thereon.
[0038] The controller 26 is calibrated such that the extent to
which the fovea 14 by itself alters the polarization state of light
incident thereon is known. On the basis of the first and second
signals, and the calibration data, the controller 26 determines the
relative contributions of the foveal and circumfoveal reflections
to the light reflected from the retina 12. The controller 26 then
generates a signal for causing the actuator 18 to change the focal
length of the lens 20 so as to cause the foveal contribution to
increase at the expense of the circumfoveal contribution.
[0039] FIG. 4 illustrates one way in which the controller 26 can
determine the relative contributions of the foveal and circumfoveal
reflections. A first polarization vector P.sub.I in FIG. 4
represents the polarization state of light incident on the retina
12, and a second polarization vector P.sub.F represents the
polarization state of the foveal reflection. A third polarization
vector P.sub.M corresponds to the measurement provided by the
detector. This third polarization vector P.sub.M represents the
combined effect of both the foveal and cicumfoveal contributions to
the reflection. It will be apparent that the foveal contribution is
the projection of the third vector P.sub.M on the second vector
P.sub.F and that the circumfoveal contribution is the remainder
thereof.
[0040] In many cases, it will not be possible to determine in which
direction the focal point should be moved. This is because it is
not possible to determine, on the basis of the relative
contributions of the foveal and circumfoveal contributions, whether
the focal plane is anterior or posterior to the retina 12.
[0041] A person who attempts to focus a pair of binoculars
encounters a similar problem. On seeing a blurry image, it is not
apparent which way one must turn the focusing knob to bring the
image into focus. Most people overcome this difficulty by turning
the focusing knob in one direction and seeing if the image becomes
more blurry, and then turning it in the opposite direction if it
does so. Similarly, the controller 26 sends a signal to the
actuator 18 to move the focal plane in one direction and observes
the change in the relative contributions of the foveal and
circumfoveal reflections. If the circumfoveal contribution
increases at the expense of the foveal contribution, the controller
26 corrects itself by sending a signal to move the focal plane in
the opposite direction.
[0042] Another embodiment of a vision prosthesis 30, shown in FIG.
5, features a lens 32 having first and second polarizing regions
36, 34 that impose orthogonal polarization states on incident
light. For example, in one embodiment, the first polarizing region
36 passes only light polarized in a first direction and the second
polarizing region 34 passes only light polarized in a second
direction orthogonal to the first direction. Consequently, light
exiting the second polarizing region 34 represents the polarizing
effect of the retinal reflection, but with the polarizing effect of
the first polarizing region 36 already removed. This light is then
provided to a detector 38. On the basis of the detected light, the
controller provides a signal to a controller 40. The controller 40
uses this signal to generate a control signal to cause an actuator
42 to adjust the focal length of the lens.
[0043] It is known that, to some extent, the cornea itself
polarizes light. Another embodiment, shown in FIG. 6, takes
advantage of this corneal polarization. In this embodiment, a first
detector 44 is disposed to receive light passing through a cornea
46 and a second detector 48 is disposed to receive light reflected
from the retina 12. Outputs of the detectors 44, 48 are then
processed by a controller 50, which provides a control signal to an
actuator 52 in the manner discussed in connection with FIG. 1.
[0044] Certain embodiments discussed above feature first and second
detectors. In those embodiments, the functions of those detectors
can be integrated into a single device.
[0045] In certain of the foregoing embodiments, one or more
polarizing regions are integral with the lens. However, this need
not be the case. The polarizing regions may be provided by discrete
elements positioned in the optical path of the lens or a portion
thereof. For example, the polarizing regions may be integrated into
a flat plate that otherwise has no optical effect.
[0046] The foregoing description uses the term "lens" to refer to
assemblies that may include one or more optical elements that
cooperate to focus incident light. The term "lens" is not to be
construed as necessarily being limited to a single refractive
element.
[0047] At least some of the embodiments described herein can be
used in conjunction with an inatraocular lens, a contact lens, or
an eyeglass lens.
[0048] Although the foregoing embodiments are shown with a single
detector for sampling a light wave, it will be appreciated that
several detectors can be provided for sampling a light wave at
several locations on the lens.
[0049] It is to be understood that while the invention has been
described in conjunction with the detailed description thereof, the
foregoing description is intended to illustrate and not limit the
scope of the invention, which is defined by the scope of the
appended claims. Other aspects, advantages, and modifications are
within the scope of the following claims.
* * * * *