U.S. patent application number 16/216648 was filed with the patent office on 2019-07-18 for systems, methods and devices for monitoring eye movement to test a visual field.
The applicant listed for this patent is Brien Holden Vision Institute Limited. Invention is credited to Brad Bower, Tom N. Cornsweet, Paul Peterson.
Application Number | 20190216311 16/216648 |
Document ID | / |
Family ID | 55351222 |
Filed Date | 2019-07-18 |
United States Patent
Application |
20190216311 |
Kind Code |
A1 |
Cornsweet; Tom N. ; et
al. |
July 18, 2019 |
Systems, Methods and Devices for Monitoring Eye Movement to Test A
Visual Field
Abstract
A method for evaluating retinal function and testing the visual
field of a patient by monitoring how the patient tracks a target
image on a display that comprises displaying the target image on
the display such that if is located at a first position on the
display and visible to the patient. The process continues by
identifying what portion of the display the patient is looking at,
selecting a location of the patient's retina to test, and
calculating, based at least in part on what portion of the display
the patient is looking at, a second position on the display
corresponding to the selected location of the patient's retina. The
target image is displayed at the second position on the display and
the process identifies how many eye movements the patient made to
look at the target at the second position. Based at least in part
on the number of eye movements, the process determines whether the
patient was able to see the target at the second position.
Inventors: |
Cornsweet; Tom N.;
(Prescott, AZ) ; Peterson; Paul; (Prescott,
AZ) ; Bower; Brad; (Hillsborough, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Brien Holden Vision Institute Limited |
Sydney |
|
AU |
|
|
Family ID: |
55351222 |
Appl. No.: |
16/216648 |
Filed: |
December 11, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15505511 |
Feb 21, 2017 |
10182716 |
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PCT/US15/45865 |
Aug 19, 2015 |
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16216648 |
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62040522 |
Aug 22, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/7282 20130101;
A61B 3/06 20130101; A61B 3/0058 20130101; A61B 3/024 20130101; A61B
3/113 20130101; A61B 5/7275 20130101 |
International
Class: |
A61B 3/024 20060101
A61B003/024; A61B 3/00 20060101 A61B003/00; A61B 5/00 20060101
A61B005/00; A61B 3/113 20060101 A61B003/113; A61B 3/06 20060101
A61B003/06 |
Claims
1. A method for evaluating retinal function and testing the visual
field of a patient by monitoring how the patient tracks a target
image on a display, the method comprising: displaying the target
image on the display, the target image being located at a first
position on the display such that it is visible to the patient;
identifying what portion of the display the patient is looking at;
selecting a location of the patient's retina to test; calculating,
based at least in part on what portion of the display the patient
is looking at, a second position on the display corresponding to
the selected location of the patient's retina; displaying the
target image at the second position on the display; identifying how
many eye movements the patient made to look at the target at the
second position; and determining, based at least in part on the
number of eye movements, whether the patient was able to see the
target at the second position.
2.-19. (canceled)
20. A device for evaluating retinal function and testing the visual
field of a patient by monitoring how the patient tracks a target
image on a display, the device comprising: a display configured to
display the target image on the display, the target image being
located at a first position on the display such that it is visible
to the patient; at least one camera assembly configured to image
the patient's eye to identify what portion of the display the
patient is looking at; and a processor configured to control the
display and the camera and to analyze the data obtained from the at
least one camera; wherein the processor is configured to: (i)
select a location of the patient's retina to test; (ii) calculate,
based at least in part on what portion of the display the patient
is looking at, a second position on the display corresponding to
the selected location of the patient's retina; (iii) display the
target image at the second position on the display; (iv) identify
how many eye movements the patient made to look at the target at
the second position; and (v) determine, based at least in part on
the number of eye movements, whether the patient was able to see
the target at the second position.
21. The device of claim 20, wherein the selection of the location
on the patient's retina is perceived as being random by the
patient.
22. The device of claim 20, wherein the processor is configured to
continue displaying the target image at a predetermined plurality
of positions on the display corresponding to predetermined
positions of the patient's retina until a map of the patient's
retina is achieved.
23. The device of claim 20, wherein, if the patient makes a single
eye movement to look at the target at the second position from the
first position, the determination is made that the patient was able
to see the target at the second position.
24. The device of claim 20, wherein, if the patient makes a more
than one eye movement to look at the target at the second position
from the first position, the determination is made that the patient
was not able to see the target at the second position.
25. The device of claim 20, wherein if the patient makes more than
one eye movement to look at the target at the second position from
the first position, the processor is configured to re-test the
second position on the retina of the patient.
26. The device of claim 20, wherein if the patient makes more than
one eye movement (e.g., more than one eye movement of M degrees) to
look at the target at the second position from the first position,
the processor is configured to identify the intermediary positions
where the patient was looking and determine, based at least in part
on the next eye movement, whether the patient was able to see the
target when the eye was at the intermediary positions.
27. The device of claim 20, wherein the position of the display is
adjustable relative to the patient to aid with focusing the
target.
28. The device of claim 20, wherein the target jumps from the first
position on the display to the second position on the display.
29. The device of claim 20, wherein the target jumps from the first
position on the display to the second position on the display after
about 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.25, 1.5, 1.75,
2, 3, 4, 5, 6, 7, 8, 9, or 10 seconds.
30. The device of claim 20, wherein the area of the patient's
retina that is measurable is approximately twice the diameter of
the patient's field of view on the display.
31. The device of claim 20, wherein there is only one target on the
display at a time.
32. The device of claim 20, wherein any combination of the
brightness, size, shape, color, or background of the target is
variable.
33. The device of claim 20, wherein the device is used, at least in
part, to aid with diagnosing and/or monitoring progression of
glaucoma.
34. The device of claim 20, wherein the device is used, at least in
part, to aid with diagnosing and/or monitoring progression of
diabetic retinopathy.
35. The device of claim 20, wherein the device is used, at least in
part, to aid with diagnosing and/or monitoring progression of
retinal artery or vein occlusion.
36. The device of claim 20, wherein the device is used, at least in
part, to aid with diagnosing and/or monitoring progression of
retinitis pigmentosa.
37. The device of claim 20, wherein the device is used, at least in
part, to aid with diagnosing and/or monitoring progression of
hemianopsia and optic tract glioma.
38. The device of claim 20, wherein the device is used, at least in
part, to aid with diagnosing and/or monitoring progression of
retinal detachment.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 62/040,522, filed on Aug. 22, 2014. This
application is also related to U.S. Provisional Application No.
61/937,788, filed on Feb. 10, 2014; U.S. application Ser. No.
13/409,056, filed on Feb. 29, 2012; International Application No.
PCT/US2012/027161, filed on Feb. 29, 2012; U.S. Provisional
Application No. 61/448,342, filed Mar. 2, 2011; and U.S.
Provisional Application No. 61/874,651, filed Sep. 6, 2013. Each of
the foregoing applications, in their entirety, are herein
incorporated by reference.
TECHNICAL FIELD
[0002] This document generally relates to systems, methods, and
devices for monitoring eye movement to test a visual field. More
specifically, the disclosure relates to systems, methods, and
devices for performing perimetry (visual field) tests without
requiring subjective patient interaction.
BACKGROUND
[0003] Conventionally, a device referred to as a perimeter is used
to perform a visual field test on a patient. The perimetry test
measures the patient's eyesight throughout the visual field (e.g,
central and peripheral).
[0004] During the test, the patient is asked to look into the
perimeter device and look forward at the center of the illuminated
area. The device is configured to flash a light on to different
areas of the display and when the patient sees the flash of light,
the patient is asked to press a button (or in some way acknowledge
they have seen the light). The device records the location of the
flash and whether the patient indicated they saw the flash and
creates a map of the patients eye indicating where the patient was
able to see the flash and where they were not able to see the
flash.
[0005] This, and other known methods, have a number of draw backs.
For example, because the patient is asked to indicate when they see
the flash while they are looking at a different place, the task is
difficult and stressful, and there is a significant margin for
error.
[0006] Accordingly, it is desirable to have systems, methods, and
devices for performing perimetry tests without requiring subjective
patient interaction and/or decision making.
SUMMARY OF EMBODIMENTS
[0007] In exemplary embodiments, perimetry may be used to evaluate
retinal function through visual field testing without the need for
subjective feedback from the patient, thereby inferring information
by analyzing the patient's eye movements.
[0008] Exemplary embodiments may provide for a method for
evaluating retinal function and testing the visual field of a
patient by monitoring how the patient tracks a target image on a
display, the method comprising: displaying the target image on the
display, the target image being located at a first position on the
display such that it is visible to the patient; identifying what
portion of the display the patient is looking at; selecting a
location of the patient's retina to test; calculating, based at
least in part on what portion of the display the patient is looking
at, a second position on the display corresponding to the selected
location of the patient's retina; displaying the target image at
the second position on the display; identifying how many eye
movements the patient made to look at the target at the second
position; and determining, based at least in part on the number of
eye movements, whether the patient was able to see the target at
the second position.
[0009] In exemplary embodiments, the target image may be a point
light source and the display may be an array of LEDs configured
such that different combinations of LEDS are illuminated to present
a target image at different locations. In general, the target image
may be any acceptable image and the display may be any device
capable of displaying the target image to the patient.
[0010] In exemplary embodiments, the selection of the location on
the patient's retina may be perceived as being random by the
patient.
[0011] In exemplary embodiments, the process continues by
displaying the target image at a predetermined plurality of
positions on the display corresponding to predetermined positions
of the patient's retina until a map of the patient's retina is
achieved.
[0012] In exemplary embodiments, if the patient makes a single eye
movement (e.g., a single saccade that hits close to the target
location and is confirmed by tracking the gaze within that
"accurate" radius around the target location) to look at the target
at the second position with a selected degree of accuracy from the
first position, the determination is made that the patient was able
to see the target at the second position and that the corresponding
portion of the retina is healthy.
[0013] In exemplary embodiments, if the patient makes more than one
eye movement to look at the target at the second position from the
first position, the determination is made that the patient was not
able to see the target at the second position and that the
corresponding area of the retina is not healthy.
[0014] In exemplary embodiments, more than one eye movement may
correspond to more than one eye movement in a predetermined time.
For example, In exemplary embodiments, more than one eye movement
may correspond to more than one eye movement in about 2 seconds, or
more than one eye movement in about 1 second, or more than one eye
movement in about 1.5 seconds, or more than one eye movement in
about 2.5 seconds, or more than one eye movement in about 3
seconds, or more than one eye movement in about 4 seconds.
[0015] In exemplary embodiments, if the patient does not make any
eye movement, (e.g., any eye movement exceeding a predetermined
threshold), the determination may be made that the patient was not
able to see the target at the second position and that the
corresponding area of the retina is not healthy
[0016] In exemplary embodiments, if the patient makes more than one
eye movement to look at the target at the second position from the
first position, the process re-tests the second position on the
retina of the patient at some subsequent step in the procedure.
[0017] In exemplary embodiments, if the patient makes more than one
eye movement to look at the target at the second position from the
first position, the process identifies the intermediary positions
where the patient was looking and determines, based at least in
part on the next eye movement, whether the patient was able to see
the target when the eye was at the intermediary positions.
[0018] In exemplary embodiments, the process may also comprise
adjusting the distance of the display relative to the patient to
focus the target.
[0019] In exemplary embodiments, the target may jump from the first
position on the display to the second position on the display.
[0020] In exemplary embodiments, the target may jump from the first
position on the display to the second position on the display after
about 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.25, 1.5, 1.75,
2, 3, 4, 5, 6, 7, 8, 9, or 10 seconds.
[0021] In exemplary embodiments, the diameter of the area of the
patient's retina that is measurable may be about twice the diameter
of the patient's field of view on the display.
[0022] In exemplary embodiments, there may only be one target on
the display at a time.
[0023] In exemplary embodiments, any combination of the brightness,
size, shape, color, or background of the target may be
variable.
[0024] In exemplary embodiments, the process may be used, at least
in part, to aid with diagnosing and/or monitoring progression of
glaucoma.
[0025] In exemplary embodiments, the process may be used, at least
in part, to aid with diagnosing and/or monitoring progression of
retinal artery or vein occlusion.
[0026] In exemplary embodiments, the process may be used, at least
in part, to aid with diagnosing and/or monitoring progression of
hemianopsia and optic tract glioma.
[0027] In exemplary embodiments, the process may be used, at least
in part, to aid with diagnosing and/or monitoring progression of
retinal detachment.
[0028] Exemplary embodiments may provide for a device for
evaluating retinal function and testing the visual field of a
patient by monitoring how the patient tracks a target image on a
display, the device comprising: a display configured to display the
target image on the display, the target image being located at a
first position on the display such that it is visible to the
patient; at least one camera assembly configured to image the
patient's eye to identify what portion of the display the patient
is looking at; and a processor configured to control the display
and the camera and to analyze the data obtained from the at least
one camera; wherein the processor is configured to: (i) select a
location of the patient's retina to test; (ii) calculate, based at
least in part on what portion of the display the patient is looking
at, a second position on the display corresponding to the selected
location of the patient's retina; (iii) display the target image at
the second position on the display; (iv) identify how many eye
movements the patient made to look at the target at the second
position; and (v) determine, based at least in part on the number
of eye movements, whether the patient was able to see the target at
the second position.
[0029] In exemplary embodiments, the selection of the location on
the patient's retina may be perceived as being random by the
patient.
[0030] In exemplary embodiments, the processor may be configured to
continue displaying the target image at a predetermined plurality
of positions on the display corresponding to predetermined
positions of the patient's retina until a map of the patient's
retina is achieved.
[0031] In exemplary embodiments, if the patient makes a single eye
movement to look at the target at the second position from the
first position, the determination may be made that the patient was
able to see the target at the second position and that the
corresponding portion of the retina was healthy.
[0032] In exemplary embodiments, if the patient makes more than one
eye movement to look at the target at the second position from the
first position, the determination may be made that the patient was
not able to see the target at the second position and that the
corresponding portion of the retina was healthy.
[0033] In exemplary embodiments, if the patient makes more than one
eye movement to look at the target at the second position from the
first position, the processor may be configured to re-test the
second position on the retina of the patient.
[0034] In exemplary embodiments, if the patient makes more than one
eye movement to look at the target at the second position from the
first position, the processor may be configured to identify the
intermediary positions where the patient was looking and determine,
based at least in part on the next eye movement, whether the
patient was able to see the target when the eye was at the
intermediary positions.
[0035] In exemplary embodiments, the position of the display may be
adjustable relative to the patient to aid with focusing the
target.
[0036] In exemplary embodiments, the target may jump from the first
position on the display to the second position on the display.
[0037] In exemplary embodiments, the target may jump from the first
position on the display to the second position on the display after
about 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.25, 1.5, 1.75,
2, 3, 4, 5, 6, 7, 8, 9, or 10 seconds.
[0038] In exemplary embodiments, the area of the patient's retina
that is measurable may be about twice the diameter of the patient's
field of view on the display.
[0039] In exemplary embodiments, there may only be one target on
the display at a time.
[0040] In exemplary embodiments, any combination of the brightness,
size, shape, color, or background of the target may be
variable.
[0041] In exemplary embodiments, the device may be used, at least
in part, to aid with diagnosing and/or monitoring progression of
glaucoma.
[0042] In exemplary embodiments, the device may be used, at least
in part, to aid with diagnosing and/or monitoring progression of
diabetic retinpathy.
[0043] In exemplary embodiments, the device may be used, at least
in part, to aid with diagnosing and/or monitoring progression of
retinal artery or vein occlusion.
[0044] In exemplary embodiments, the device may be used, at least
in part, to aid with diagnosing and/or monitoring progression of
hemianopsia and optic tract glioma.
[0045] In exemplary embodiments, the device may be used, at least
in part, to aid with diagnosing and/or monitoring progression of
retinal detachment.
DESCRIPTION OF THE DRAWINGS
[0046] Notwithstanding any other forms which may fall within the
scope of the disclosure as set forth herein, specific embodiments
will now be described by way of example and with reference to the
accompanying drawings in which:
[0047] FIG. 1 is a schematic diagram of an exemplary device for use
in monitoring and/or measuring eye movement in response to stimuli
provided on a display;
[0048] FIG. 2 is a flow chart describing an exemplary process for
monitoring and/or measuring eye movement in response to stimuli
provided on a display; and
[0049] FIGS. 3A and 3B are diagrams describing an exemplary process
for calculating off-screen positions of stimuli in accordance with
the process described in FIG. 2.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0050] This document describes methods, systems and devices for
using eye movement perimetry to evaluate retinal function through
visual field testing without the need for subjective feedback from
the patient, thereby inferring information by analyzing the
patient's eye movements. The concept of eye-movement perimetry may
be more easily understood if certain common terms are initially
explained.
[0051] In exemplary embodiments, the term "grid" may be utilized to
describe a set of locations across the visual field of a patient's
retina. In exemplary embodiments the grid may be designed for a
particular purpose (e.g., screening for glaucoma).
[0052] In exemplary embodiments, a "session" may refer to the
perimetry related activity that occurs for a particular patient.
For example, in exemplary embodiments, a session may encompass all
of the perimetry related activities during a patient's visit and
may involve one or more tests. Similarly, tests may be more
specific in their design (i.e., a quick glaucoma test) and composed
of a sequence of trials.
[0053] In exemplary embodiments, the term "target" may be used to
describe a visible dot (or other shape) on a display that is viewed
by the patient. As described herein, in exemplary embodiments, only
one target may be presented at a time. In exemplary embodiments,
the target may jump to/from various parts of the display.
[0054] In exemplary embodiments, the term "test" may refer to a
sequence of trials that are executed to move the target across
multiple (e.g., many or all) positions on the display specified by
a selected grid.
[0055] In exemplary embodiments, the term "trial" may refer to a
time interval starting with the subject fixated on the target, and
ending when the target jumps to a new location and the subject
successfully finds and fixates on the new target via one or more
eye movements (i.e., saccades).
[0056] In exemplary embodiments, a purpose of eye movement
perimetry may be to perform automated perimetry. Accordingly, in
exemplary embodiments, a patient may look into a device and through
a lens at a target presented on a display, for example an LCD
display. The distance between the lens and the display may be
adjusted so that the target appears reasonably sharp. The operator
of the device may then start a preliminary training period, during
which the target jumps abruptly from one location on the display to
another location on the display in an apparently random pattern.
The patient may be asked to keep looking directly at the target and
to follow it with their eyes. In exemplary embodiments, during
training, an indication (e.g., an audio or visual indication) may
be presented that indicates whether or not the patient is correctly
fixating on the spot.
[0057] After the target is displayed for a fixed interval, e.g.,
0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.25, 1.5, 1.75, 2, 3,
4, 5, 6, 7, 8, 9, or 10 seconds, the device may determine where the
patient is looking on the display. Utilizing this information, the
device may determine where on the display the target should jump to
so that the image of the target falls on a retinal location that is
intended to be tested next. In exemplary embodiments, the target
may move, instantaneously (or very quickly), to a new position on
the display. In exemplary embodiments, the target may be referred
to as "jumping" from one position on the display to another. As
would be readily understood, this may be accomplished in a variety
of manners. For example, the target may be illuminated at one
position of the display and then after it is turned off at that
position of the display, illuminated on a second position of the
display. Alternatively, the target may be illuminated at the second
position of the display before it is turned off on the first
portion of the display. In either case, the perception is that the
target is "jumping" from one position to another. Further, in
exemplary embodiments there may not be more than one target on the
display at any given time. In exemplary embodiments, the target may
not be displayed for a fixed interval. Instead, it may be displayed
until the patient has been correctly looking at the target position
for some fixed interval, e.g., 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,
0.9, 1, 1.25, 1.5, 1.75, 2, 3, 4, 5, 6, 7, 8, 9, or 10 seconds. For
example, if a patient requires more than one saccade to reach the
target, the time before the next target may be longer.
[0058] As will be appreciated by persons of ordinary skill in the
art, there is a difference between having the target merely move
among fixed places on the display and among places on the display
that will test the desired spots on the retina.
[0059] In general, where the patient is looking (or fixating) may
be described as the eye being rotated to a position such that the
image or point that the patient is looking at falls on the fovea of
the patient's eye. As would be understood by a person of ordinary
skill in the art, there is a tiny region, near the center of the
retina, called the fovea, where the highest density of
photoreceptor cells exists. When a target is displayed at a point
at a different place than where he or she is currently looking, the
image of the point will fall somewhere on the retina away from the
fovea. As a result, the visual system will determine a new set of
tensions that the eye muscles (six on each eye) must take up to
cause the eye to rotate to the correct position, the muscles are
instructed to change their tensions accordingly and the eye rotates
such that the retina slides beneath the image of the new point.
When the movement or movement series is complete, the image of the
new point falls on the fovea once again.
[0060] When a target jumps from its current location to a new
location, a typical reaction time may be about 200 milliseconds.
That is, about 200 ms elapse between the time the target first
jumps and the time the patient begins to make a corresponding eye
movement. If the retinal region that the image of the target falls
on before the eye movement occurs is healthy, the patient may make
a fast, single, ballistic eye movement (called a saccade), which
will cause the retina to slide under the image of the target, and
when the saccade ends, the patient will be looking at the new
target position. However, if the target fell on a blind spot, the
patient may make a saccadic movement to some location different
from the target position, which will move the image of the target
to a different retinal location. If, after that movement, the
target falls on healthy retina, the patient may make a second
saccadic movement such that he or she will be looking at the new
target position.
[0061] Exemplary embodiments described herein may utilize a device
capable of performing the perimetry methods described. For example,
in embodiments, a device that generates the target to an eye while
monitoring and/or measuring the resulting eye movements may be
provided. The resulting eye movements may be analyzed by a
processor and the analysis may be performed in real time or
substantially real time.
[0062] In exemplary embodiments, the device may consist of three
main components or subsystems. One subsystem may be responsible for
display of the targets on a display. Another subsystem may monitor
movement of the eye. The third subsystem may be a
computer/processor and/or software that controls the first two
subsystems, analyzes the results, and/or provides a user
interface.
[0063] FIG. 1 is a schematic diagram of an exemplary device for use
in monitoring and/or measuring eye movement in response to stimuli
provided on a display. As illustrated, the device 100 is configured
to allow an individual to look into the device via a window 102.
When the individual looks into the device, the individual looks
through a viewing lens 104 and at a display 106. The display 106
may be moved relative to the viewing lens 104. In addition, the
device 100 may comprise one or more LEDs 108 for illuminating the
eye or eyes of the individual. In exemplary embodiments, the LED(s)
108 may be located adjacent to the viewing lens 104. In exemplary
embodiments, one or more LEDs may be provided for the eye. In
exemplary embodiments, the LEDs may be infrared LEDs.
[0064] In exemplary embodiments, the LED(s) may illuminate the
individual's eyes and a portion of the light may be reflected from
the eyes and onto mirror 110. In exemplary embodiments, the mirror
110 may be an adjustable mirror 110. The light may then be captured
by a camera 114. The images captured by the camera may be sent to a
computer/processor for analysis. In exemplary embodiments, the
adjustable mirror 110 may be driven by a motor (not shown) to
rotate the adjustable mirror 110 about a substantially horizontal
axis through the center of the adjustable mirror 110 and a second
motor (not shown) may rotate the mirror abdut an axis at 90 degrees
to the horizontal and in the plane of the mirror. In exemplary
embodiments, the motor may be driven by the computer/processor to
adjust the image as necessary. For example, the computer may adjust
the motor such that the image of the pupil is roughly centered in
the camera view. In exemplary embodiments, this may compensate for
patients whose eyes are higher or lower with respect to the nose
bridge.
[0065] Additionally, in exemplary embodiments, the optical system,
including e.g., the display, may be driven by another motor (not
shown) towards and/or away from the individual, to focus the images
of the pupils, as desired.
[0066] In exemplary embodiments, the display may be moved relative
to the viewing lens.
[0067] As may be appreciated from the above description, in
exemplary embodiments, the field of view of the patient in the
instrument/device may be limited in size by the optics between the
eye and the display, and by the distance between the optics and the
eye. For example, in exemplary devices the field of view may be
limited to 30 degrees. However, the region of the retina that can
be mapped in this way is twice the diameter of the patient's field
of view.
[0068] For example, suppose that a patient is looking at the center
of a 30 degree field and the target jumps horizontally to the edge
of the field--a 15 degree jump on the field and on the retina.
After completion of that saccade or sequence of saccades, suppose
the target jumps horizontally to the opposite edge of the 30 degree
field of view--the target will now be imaged on the retina 30
degrees away from the fovea, so 30 degrees is the radius of the
region that can be mapped.
[0069] Accordingly, in exemplary embodiments, mapping may consist
of placing a target at various places on the retina and observing
the resulting eye movements. The eye movements may indicate whether
or not the various positions on the retina are healthy. In
exemplary embodiments, the resulting data may include retinal
points that were not initially selected for mapping. Suppose, for
example, that the image of the target jumps to a blind region of
the retina. The patient may make an initial eye movement that is
incorrect, followed by one or more movements until the target is
correctly fixated. After the initial movement, the image of the
target now falls on a different region of the retina (e.g., a
region not necessarily among those that were intended to be
tested). If the patient then makes a correct eye movement, that
region of the eye can be scored as "healthy" or "seen", and if,
instead, still another eye movement occurs, that region of the
retina can be scored as "not healthy" or "not seen".
[0070] In exemplary embodiments, it may be desirable to add target
positions into the sequence of targets that are not in the set
originally intended to be tested. For example, the patient may be
looking at a point 10 degrees to the right of the center of the
display, and the next point to be tested may be more than 5 degrees
to the right of the fovea. Because the field of view has a radius
of only 15 degrees, the next target will not fit within the field
of view of the display. Instead, a new target position, e.g., 10
degrees to the left of center, may be inserted into the sequence
and the patient may look at that point and then the desired point
can be reached.
[0071] In exemplary embodiments, the patient's eye movements may be
saved to construct a visual field map. During the procedure, the
processor may abruptly move the target every T seconds (e.g., 0.2,
0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.25, 1.5, 1.75, 2, 3, 4, 5,
6, 7, 8, 9, or 10 seconds) in such a way that, by the end of the
procedure, the target has jumped to the locations on the patient's
retina that were desired to be tested.
[0072] As discussed above, in exemplary embodiments, the location
of the target on the display may be selected to correspond to a
desired location of the patient's retina. Accordingly, in exemplary
embodiments, the processor may need to be aware of two different
surfaces and their different coordinate systems. One surface is the
surface of the display within the instrument; the other is the
surface of the patient's retina. When the patient looks at the
target, the patient's external eye muscles rotate their eyes until
the retinal image of the spot falls on the fovea. In exemplary
embodiments, the device may continuously track the patient's
direction of gaze with respect to the display. That is, the
locations of the fovea and of the other points on the retina are
known with respect to the display and a mapping between the
patient's retina and the display is established. Since the display
maps to some area of the retina that will be smaller than the
entire retina, if it is desired to test whether a particular point
of the retina is sensitive to light, the system first computes
whether or not the point to be tested is within the area mapped to
the display. If it is not, then it cannot be tested yet (but may be
later, as explained below). If the retinal point to be tested does
correspond to a point on the display, then the target can be moved
to that point on the display, thus jumping the retinal image of the
target on to the point on the retina that is to be tested.
[0073] As discussed above, if the point on the retina is sensitive
to light (and if the patient is following the appropriate
instructions), the patient will make what is called a "saccadic"
eye movement. Specifically, after a minor delay, the eyeball will
abruptly begin to rotate in a single very fast movement and will
abruptly stop rotating in a position such that the retinal image of
the test spot will again fall on the fovea. This kind of movement
is ballistic. During the approximately 200 milliseconds after the
target moves to the new position but before the eye begins to move,
the brain computes the extent to which it must change the tensions
in each of the eye muscles. The results of those calculations are
then abruptly sent to the muscles, which execute the commands in
the next few milliseconds. As a consequence, once a saccadic eye
movement has been initiated, it will run its predetermined course.
For example, if the stimulus spot jumps from A to B and then, while
the saccade to B is occurring, the target moves to C, the eye will
pause at B, wait about 200 milliseconds, and then make a new
saccadic movement to C.
[0074] In contrast, if the target jumps to a spot on the retina
that is insensitive to light, the following events may occur. The
target may disappear from the patient's vision, and as a
consequence, after a 200 millisecond delay, the patient may
actually make a saccadic eye movement, but its direction and
amplitude may be independent of the actual location of the test
spot. This saccadic movement will shift the retina under the image
of the target and so, when the saccadic movement ends, the image of
the target may fall on some new region of the retina, and that
region may be light-sensitive. Therefore, after another 200
milliseconds, the patient may make a new saccadic eye movement in
such a direction and amplitude that the image of the target falls
on the fovea.
[0075] Therefore, if a target moves to a new location and the eye
is being accurately tracked, the sensitivity of the retinal
location to which the target moved may be revealed. That is, if a
single saccadic movement brings the eye to correctly fixate on or
close to the spot, the location on the retina was responding to the
target. If such a single movement did not occur, the retinal
location may have a sensitivity too low to detect the target.
[0076] In exemplary embodiments, the patient may experience a trial
in which a target jumps every few seconds to a new, apparently
randomly selected location, and every once in a while, the spot may
appear to briefly turn off. If the direction of gaze of the eye is
constantly and accurately tracked, then it may be possible to know
the mapping between the spatial coordinates of the retina and those
of the display screen. That is, one can decide to test the
sensitivity of any point on the retina that is mapped to within the
area of the display and present a test flash at a location on the
display that will correctly deliver the image of the target to the
retinal point to be tested.
[0077] As discussed above, the eye movement perimeter device may
consist of three subassemblies, one that tracks the patient's eye,
a second that displays targets on a display, and a third, that
controls the actions of the other two and/or the user
interface.
[0078] In exemplary embodiments, the process for measuring a
patient's perimetry may begin with an operator entering the
patient's data (e.g., ID number, name, and any other desired data).
The operator may select the form of the test to be performed, such
as a "quick glaucoma screener". The operator then asks the patient
to rest against a head-positioning device, which may consist of a
forehead rest, nose bridge rest, or a chin rest, and look into the
instrument at a small flashing spot of light straight ahead. An
image of the region including the front of the patient's eye may
appear on the operator's screen, the operator may use a mouse to
drag the image until the pupil is roughly centered in a window, and
then initiate the test. In exemplary embodiments, the remaining
portion of the test may proceed automatically (or in a
semi-automated manner in which e.g., an operator may mark out
regions of the retina to return to for further analysis, e.g.,
mapping in finer detail any blind spots), under the control of the
internal processor. The device may examine the image of the eye and
find markers for its direction of gaze. For example, in an
implementation, the center of the pupil and the location of the
image of a light source formed by reflection from the cornea may be
computed and the relative positions of the two may define the
direction of gaze. As would be readily understood by persons of
skill in the art, there are several eye-tracking methods available
and the particular one used may be immaterial so long as it
provides a measure not merely of the location of the eye but rather
of the angular position of the eye, that is, the direction of
gaze.
[0079] The target then suddenly jumps to a new position on the
display, one that corresponds to one of the locations on the retina
that is to be tested. After a delay of duration to be determined
but of approximately two seconds, the eye will have moved to a new
direction of gaze that corresponds to the new display stimulus
position, thus shifting the mapping between the display and the
retina. The internal computer evaluates whether or not the first
saccadic movement was essentially correct and records that data.
The processor then identifies another of the retinal locations to
be tested, one that maps to some location on the display, and jumps
the stimulus to that new position. This general procedure continues
until the retinal locations to be tested have been stimulated. The
same process occurs for any additional saccades that occur before
the new target is fixated.
[0080] FIG. 2 is a flow chart describing an exemplary process for
monitoring and/or measuring eye movement in response to stimuli
provided on a display. In exemplary embodiments, the process for
measuring eye movement may begin by creating a table (or list) of
retinal positions to test. The table may comprise a column for
"Tested", another for "Seen", another for "not seen once", another
for "not seen twice." The table may be referred to as a "map
table." A "saccade" may be defined as a single movement that begins
and ends with movement smaller than M degrees during e.g., a 100
msec period and a correct saccade may be defined as a saccade with
a gaze direction ending within a predefined number of degrees (D)
of the target on the display.
[0081] With this initial set-up, the process exemplified in FIG. 2,
begins by displaying the target in the middle of the display. The
location on the display where the patient is looking is recorded.
In the next step, a next retinal location from the map table is
randomly selected from a group of positions in the set comprising
the untested positions and the unseen positions. Based on the
selected retinal location and the current gaze direction of the
patient, the process continues by computing a corresponding
location for the target on the display. If the target is too close
to the previous target, the process will select a new target. If
the target corresponds to a location that is off the display, the
process continues by calculating an off screen position as
described with respect to FIGS. 3A and 3B. If the target is not too
close and on the display, the target is displayed and the movement
of the patient's eyes are tracked. Next a determination is made as
to whether the saccade was an accurate movement and if it was, the
process records that the target was seen for the corresponding
retinal position. If the saccade is not accurate, the position is
marked as having been tested but not seen. In addition, in
exemplary embodiments, it may be possible to obtain additional
information from the incorrect saccade. For example, if there are
more than two saccades (i.e., a initial movements to an incorrect
location and last movement to the correct location), each of the
retinal positions of the targets that produce the initial incorrect
movements may be recorded as not seen retinal locations. In
exemplary embodiments, it may be desirable to test unseen positions
twice before concluding that the position is a blind spot.
Accordingly, if the position is unseen for the first time, it may
be added to the group of unseen positions so it can be tested again
at a later, random time.
[0082] After all of the positions in the untested group and the
unseen group have been tested, the test may conclude.
[0083] In exemplary embodiments, it may be desirable to perform
threshold perimetry testing. In this case, the map table may be
expanded such that, instead of just the points to be tested being
listed in the table, the points are listed with a plurality (e.g.,
2, 3, 4, 5, 6, 7, 8, 9, and/or 10) of corresponding brightnesses,
sizes, shapes, colors, backgrounds, or other variations. In this
manner, a single point may be expanded to a plurality of points
having the same location but varying brightnesses, shapes, colors,
backgrounds, or other variations.
[0084] In exemplary embodiments, it may be desirable to perform
scotoma mapping. In this embodiment, a standard map table may be
set up and perimetry performed as described above. However, if a
"not seen" point is identified, a new set of points may be added to
the table that lie in a circle D degrees (for example 1, 2, 3, 4,
and/or 5 degrees) from the "not seen" point. If any of those points
are "not seen", further points are added on an arc D degrees in
radius and in a direction away from the previously unseen
point.
[0085] FIGS. 3A and 3B are diagrams describing an exemplary process
for calculating off-screen positions of stimuli in accordance with
the process described in FIG. 2. As discussed above, when a retinal
position is selected, a corresponding position to display the
target on the display is calculated to test that retinal position.
In some instances, the calculated position may not lie on the
display itself. Accordingly, it may be necessary to rely on an
intermediate point. As illustrated in FIGS. 3A and 3B, a present
display location (1), an intermediate point on the edge of the
display (2) and a desired off screen point (3) are identified.
Using this information, it may be possible compute the distance (L)
from point (1) to point (3) and compute the angle (relative to a
horizontal). Next, using this information, a new point (4) is
identified. Point 4 is on a line at the same angle and at a
distance from point (C--e.g., Center of the Display) that equals
the distance from point 1 to point 3 and passes through point (C).
Using this new position (4), the process can create a circular area
centered around point (4) with a radius of R*SF (where R is the
radius of the display and SF is a scale factor to ensure the point
lies on the display). Then an intermediate point is randomly
selected. If the intermediate point is contained within the
intersection of the space within the display and the circular area
defined around point (4), then it is used as the next target
position. The patient moves their gaze to the intermediate position
and then from that position, a new position on the display is
calculated corresponding to the originally selected retinal
position.
[0086] In exemplary embodiments, the process may comprise multiple
tests that may have more or less points tested in a wider or
narrower visual field angle, e.g., the Humphrey 30-2 visual field
test tests 30 degrees around the fovea while the 10-2 visual field
test tests 10 degrees around the fovea (a central vision test). In
exemplary embodiments, it may be desirable to test a small number
(e.g. 10 points per quadrant=40 points) or a much larger number
(70-100+) of points. It may also be desirable to irregularly sample
the grid (e.g., have a non-uniform sampling such that the test can
more heavily sample regions of interest, e.g., blind spots).
[0087] In exemplary embodiments, when the target moves and the
patient is correctly fixating it (within some predefined degree of
accuracy), a tone may be sounded. Further, the first number of
trials may be regarded as training trials to acquaint the patient
with the task and to make sure the patient is able to perform it.
For example, there may be occasional patients who, due to brain or
muscle pathology, are unable to make accurate saccadic
movements.
[0088] In exemplary embodiments, if the procedure reveals one or
more retinal locations that did not trigger an accurate saccadic
movement, those locations may be automatically retested during
trials that are imbedded into the stimulus sequence.
[0089] In exemplary embodiments, when such a sequence is complete,
the device may display and/or print a map showing the sensitivities
of the various points on the retina that have been tested.
[0090] In exemplary embodiments, there may be one or more
advantages to using this method over conventional perimetry
methods. For example, the information about whether or not each
point tested is seen may be determined more objectively.
Accordingly, the patient doesn't need to make any judgments. In
exemplary embodiments, the described procedure may be more natural
to the patient because they do not have to decide whether or not a
target was seen when it was not where he or she was looking. As a
result, in exemplary embodiments, patient anxiety may be reduced
and/or the results of the tests may be less variable. Using the
standard procedure, the patient tries to look steadily at a
stationary target straight ahead while looking for flashes off to
the sides. Since the patient may not be looking at the stationary
target when the test flash is delivered the flash may not be
delivered to the place on the retina that was intended to be
tested, and an erroneous datum may be produced on the visual field
map. However, as described in connection with the exemplary
methods, when the direction of gaze is tracked and the target is
positioned in accordance with that direction, then the point tested
on the retina is known and is the one intended to be tested.
Therefore, erroneous trials are eliminated (or at least
significantly reduced) and the resulting visual field maps are more
accurate.
[0091] Some perimeters that use the standard procedure include some
form of eye tracking, such as a video camera that images the eye
and displays an image which the operator can watch. If the operator
notices that the eye appears not to be pointed correctly during a
trial, the operator usually just uses the information to remind the
patient to fixate on the target, and in some instruments he or she
can signal the perimeter to ignore that trial. The procedure
described herein does not require rejection of trials, and so may
be more efficient and thus faster.
[0092] In exemplary embodiments, the device may be configured such
that the position of the new stimulus on the retina is known.
Specifically, the device may determine where the patient is
actually looking, that is, where the retinal coordinates are with
respect to the coordinates of the display, and then determine where
on the display to place the next target so that it will actually
fall on the retina in the location that is desired.
[0093] In exemplary embodiments, the position of the next target
may be selected such that it appears random to the patient. In this
manner, the patient is unable to predict where the next target will
be. Additionally, in exemplary embodiments, the target may not jump
back to the same place after the new position is tested--it just
jumps to the new, unpredictable (to the patient) position. At least
one previously described attempt to do perimetry by evaluating eye
movements has the target jump back to the center after each new
spot is tested. It has been realized that when the target jumps
back to a center position after each new position is tested,
patients may simply keep looking at the center and wait for the
target to jump back there. The tendency to do that may be very hard
to overcome even if the patient tries to resist it.
[0094] In exemplary embodiments, if the patient's eye movements
indicate that he or she did not see the target when it jumped to a
particular position, then a second test for that spot on the
retina, may be automatically inserted into the testing sequence. In
exemplary embodiments, the second test may be inserted in a manner
that causes it to appear unpredictable/random to the patient.
[0095] In exemplary embodiments, the general procedure described
herein may be performed with a variety of different types of
targets and retinal locations. For example, the target spot can
always have the same intensity or it may have varying intensities.
In the case of a fixed intensity, the sensitivity map may, at the
points tested, be binary, and if the brightness is set so that a
patient with a healthy visual system will see all the points except
those in the optic disk, the map will indicate blind spots, called
scotomas. Alternatively, the targets can be delivered at a range of
brightnesses, and the sensitivity map may become three-dimensional,
for example, with height indicating the intensity necessary for the
target to be seen.
[0096] In exemplary embodiments, the number and distribution of the
tested points can also be varied. For example, just twenty points,
in regions most likely to be affected by glaucoma, can be tested as
a quick glaucoma screening.
[0097] In general, the target can be any color. For example, the
target may be a small white spot on a dark display or, for
specialized testing, the spot may be blue on a yellow
background.
[0098] In exemplary embodiments, one eye may be tested at a time
and both eyes may be tested in the same session.
[0099] In exemplary embodiments, the systems, devices, and methods
described herein may be beneficial in diagnosing and/or monitoring
progression of various diseases that affect the visual field. The
eye is composed of three primary structures--the cornea, the lens,
and the retina. Light travels through the cornea and lens to the
retina to be sensed by the retina. Trauma or disease can obstruct
the path of light through the eye. For example, corneal scarring
(e.g., due to trachoma) or clouding of the lens (e.g., due to
cataract) may obstruct the path of light to the retina. The retina
is composed of a layer of photosensitive cells and signal
transduction and processing layers. Light is transduced from
photons into neural signals at the photosensitive layer (the
photoreceptors). The signal from many photoreceptors is passed to
fewer bipolar cells, which then pass to even fewer ganglion cells.
This many-to-one relationship provides some of the early processing
of visual information before light is conducted to the brain.
Damage to any of these layers can create a portion of the eye that
is not able to properly transduce light into neural signals.
[0100] In exemplary embodiments, the systems, devices, and methods
described herein may be beneficial in diagnosing and/or monitoring
progression of glaucoma. Glaucoma is a neuro-degenerative disease
in which the ganglion cells die. This can cause regions of visual
field loss, typically in the superior and inferior aspects of the
eye. Glaucoma may be detectable with the described systems,
devices, and methods.
[0101] In exemplary embodiments, the systems, devices, and methods
described herein may be beneficial in diagnosing and/or monitoring
progression of retinal artery or vein occlusion. Blood vessels in
the eye can become partially or completely occluded by a
thrombosis, leading to regions of the retina that are not perfused.
Lack of perfusion (i.e., ischemia), which can lead to regions of
tissue death and visual field loss. These issues may be detectable
with the described systems, devices, and methods.
[0102] In exemplary embodiments, the systems, devices, and methods
described herein may be beneficial in diagnosing and/or monitoring
progression of retinitis pigmentosa. Retinitis pigmentosa is a
disease affecting the photosensitive cells in the eye, the rods and
cones. RP is typically characterized by peripheral vision loss
leading to tunnel vision as the rod cells in the eye are lost. Some
types of retinitis pigmentosa affect the cone cells as well and can
lead to progressive, total visual field loss. These issues may be
detectable with the described systems, devices, and methods.
[0103] In exemplary embodiments, the systems, devices, and methods
described herein may be beneficial in diagnosing and/or monitoring
progression of hemianopsia and optic tract glioma. Hemianopsia and
optic tract glioma are conditions in which half or more of the
visual field is lost due to trauma or disease (typically a lesion
or tumor). In hemianopsia, half of the visual field will be lost in
both eyes, e.g., the right half of the field in both eyes. Lesions
in the brain can even lead to quadrantopsia, in which one quadrant
of the visual field will be missing from both eyes. These issues
may be detectable with the described systems, devices, and
methods.
[0104] In exemplary embodiments, the systems, devices, and methods
described herein may be beneficial in diagnosing and/or monitoring
progression of retinal detachment. Disease or trauma can lead to a
retinal detachment, a condition in which some or all of the layers
of the retina pull away from other tissues of the eye. Vision loss
occurs at the site of the detachment. This issue may be detectable
with the described systems, devices, and methods.
[0105] In exemplary embodiments, the systems, devices, and methods
described herein may be beneficial in diagnosing and/or monitoring
progression of multiple sclerosis. Optic neuritis associated with
multiple sclerosis may lead to partial or full blindness in one or
both eyes. These issues may be detectable with the described
systems, devices, and methods.
[0106] While exemplary embodiments have been shown and described
herein, it will be obvious to those skilled in the art that such
embodiments are provided by way of example only. It is intended
that the following claims define the scope of the invention and
that methods and structures within the scope of these claims and
their equivalents be covered thereby.
* * * * *