U.S. patent application number 15/355890 was filed with the patent office on 2017-03-09 for quantification of inter-ocular suppression in binocular vision impairment.
The applicant listed for this patent is The Schepens Eye Research Institute, Inc.. Invention is credited to Peter Bex.
Application Number | 20170065168 15/355890 |
Document ID | / |
Family ID | 54554708 |
Filed Date | 2017-03-09 |
United States Patent
Application |
20170065168 |
Kind Code |
A1 |
Bex; Peter |
March 9, 2017 |
QUANTIFICATION OF INTER-OCULAR SUPPRESSION IN BINOCULAR VISION
IMPAIRMENT
Abstract
Systems, apparatus, and methods are provided for quantifying
inter-ocular suppression in binocular vision impairment. The
systems, apparatus, and methods may include a stimulus presentation
device and a controller which present different stimuli to each eye
of a patient. The stimuli can include letters, numbers, or shapes
which are arranged in rows, and columns with a stimulus presented
to each eye in a location corresponding a stimulus presented to the
other eye. The combined contrast of corresponding stimuli equals a
predetermined value, and this contrast can be adjusted with each
iteration of stimuli presented. This adjustment can be based upon
the patient's reports of what is seen and adjustments made by an
algorithm executed by the controller. Suppression can thus be
determined in terms of visual field location and quantified.
Inventors: |
Bex; Peter; (Concord,
MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Schepens Eye Research Institute, Inc. |
Boston |
MA |
US |
|
|
Family ID: |
54554708 |
Appl. No.: |
15/355890 |
Filed: |
November 18, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/IB2015/001201 |
Jul 17, 2015 |
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15355890 |
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PCT/US2015/041033 |
Jul 17, 2015 |
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PCT/IB2015/001201 |
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PCT/US2015/031806 |
May 20, 2015 |
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PCT/US2015/041033 |
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62000988 |
May 20, 2014 |
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62000988 |
May 20, 2014 |
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62000988 |
May 20, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 2027/0112 20130101;
G02B 2027/014 20130101; G02B 2027/0178 20130101; G02B 2027/011
20130101; G02B 27/017 20130101; A61B 3/08 20130101; G02B 2027/0134
20130101; A61B 3/032 20130101 |
International
Class: |
A61B 3/08 20060101
A61B003/08; G02B 27/01 20060101 G02B027/01; A61B 3/032 20060101
A61B003/032 |
Goverment Interests
GOVERNMENT LICENSE RIGHTS
[0002] This invention was made with government support under R01
EY021553 awarded by National Eye Institute of the U.S. National
Institutes of Health. The government has certain rights in the
invention.
Claims
1. A system for quantifying suppression in binocular vision of a
patient, the system comprising: a stimuli presentation device
configured to present stimuli comprising a distinct stimulus for
each eye of the patient; and a controller, operably connected to
the stimuli presentation device, the controller comprising: a
computer comprising an interface configured to accept input from a
clinician, a patient, or both; an adaptive algorithm executed on
the computer, the adaptive algorithm configured to accept a report
describing what the patient sees when presented with the stimuli
and calculate adjustments to the stimuli to be presented in the
next iteration of stimuli; and a stimulus generating component
configured to provide the next iteration of stimuli to the patient
via the stimuli presentation device.
2. The system of claim 1, wherein the stimuli presentation device
comprises 3D stereo shutter glasses, anaglyph glasses, polarized
lenses, a Wheatstone stereogram, head mounted displays, lenticular
screens, or any combination thereof.
3. The system of claim 1, wherein the system is configured to
measure scale dependent suppression in the binocular vision of the
patient.
4. The system of claim 3, wherein the stimuli comprise bandpass
filtered Sloan letters laid out in a manner comprising multiple
rows of letters, each row of decreasing letter size, and each row
having multiple letter, wherein each letter in a row is distinct
and having a different amount of contrast.
5. The system of claim 4, wherein each distinct stimulus for each
eye of the patient has the same number of rows of letters and
columns of letters, wherein a letter on a right eye stimulus
corresponds to a letter on a left eye stimulus in a similar
position, further wherein the corresponding letters have a combined
contrast that is a fixed value.
6. The system of claim 3, wherein the Sloan letters of the stimuli
comprise peak spatial-frequencies of 0.5 to 10 cycles per
degree.
7. The system of claim 3, wherein the Sloan letters create a
pattern that covers a main area of a contrast sensitivity
function.
8. The system of claim 1, wherein the system is configured to
measure suppression in the binocular vision of the patient while
each eye of the patient is fixated on a spot on the distinct
stimulus presented to each eye.
9. The system of claim 1, wherein the system is configured to
measure both visual-field and spatial-frequency dependent
suppression in the binocular vision of the patient.
10. The system of claim 1, wherein the stimuli comprise numbers or
colored dots.
11. A method comprising: presenting, via a computer controller and
a stimuli presentation device, stimuli to a patient, the stimuli
comprising a distinct stimulus for each eye of the patient;
accepting, via the computer controller, reports comprising
observations from the patient regarding the stimuli; creating an
adjusted stimuli via an adaptive algorithm executed on the computer
controller, the adaptive algorithm using the reports as input; and
presenting to the patient the adjusted stimuli via a stimulus
generating component of the computer controller and the stimuli
presentation device.
12. The method of claim 11, further comprising evaluating the
reports to determine whether suppression in binocular vision of the
patient can be quantified.
13. The method of claim 11, further comprising quantifying
suppression in binocular vision of the patient.
14. The method of claim 11, wherein the stimuli comprise bandpass
filtered Sloan letters, numbers, or colored dots.
15. The method of claim 14, wherein a stimulus for a right eye and
a stimulus for a left eye comprise corresponding features, the
features comprising the bandpass filtered Sloan letters, numbers,
or colored dots.
16. The method of claim 15, wherein each feature has a contrast
value, further wherein a sum of the contrast values for
corresponding features equals a fixed amount, the fixed amount
being the same for each pair of corresponding features.
17. A non-transitory computer-readable medium encoded with
instructions that, when executed by at least one processor, cause
operations comprising: presenting, via a computer controller and a
stimuli presentation device, stimuli to a patient, the stimuli
comprising a distinct stimulus for each eye of the patient;
accepting, via the computer controller, reports comprising
observations from the patient regarding the stimuli; creating an
adjusted stimuli via an adaptive algorithm executed on the computer
controller, the adaptive algorithm using the reports as input; and
presenting to the patient the adjusted stimuli via a stimulus
generating component of the computer controller and the stimuli
presentation device.
18. An apparatus comprising: means for presenting, via a computer
controller and a stimuli presentation device, stimuli to a patient,
the stimuli comprising a distinct stimulus for each eye of the
patient; means for accepting, via the computer controller, reports
comprising observations from the patient regarding the stimuli;
means for creating an adjusted stimuli via an adaptive algorithm
executed on the computer controller, the adaptive algorithm using
the reports as input; and means for presenting to the patient the
adjusted stimuli via a stimulus generating component of the
computer controller and the stimuli presentation device.
19. The apparatus of claim 18, further comprising evaluating the
reports to determine whether suppression in binocular vision of the
patient can be quantified.
20. The apparatus of claim 18, further comprising quantifying
suppression in binocular vision of the patient.
21. The apparatus of any of claim 18, wherein the stimuli comprise
bandpass filtered Sloan letters, numbers, or colored dots.
22. The apparatus of claim 21, wherein a stimulus for a right eye
and a stimulus for a left eye comprise corresponding features, the
features comprising the bandpass filtered Sloan letters, numbers,
or colored dots.
23. The apparatus of claim 22, wherein each feature has a contrast
value, further wherein a sum of the contrast values for
corresponding features equals a fixed amount, the fixed amount
being the same for each pair of corresponding features.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. provisional
patent application Ser. No. 62/000,988, attorney docket number
36770-545P01US, filed on May 20, 2014, and entitled "QUANTIFICATION
OF INTER-OCULAR SUPPRESSION IN BINOCULAR VISION IMPAIRMENT," which
is incorporated by reference herein in its entirety.
FIELD
[0003] The subject matter described herein relates to systems,
apparatus, and methods related to the assessment of the condition
of a patient's vision, particularly for assessing the impairment of
a patient's binocular vision.
BACKGROUND
[0004] Eye disease may cause asymmetric visual impairment in each
eye. One eye of a patient may have better vision in one eye as a
consequence of eye disease or a congenital disorder. The loss of
vision in one of the patient's eye is often compensated for by
healthy vision in the other eye for the same location. The better
of the combined vision of the two visual fields for each eye, that
is the monocular visual fields for each eye, makes up the binocular
visual fields for a patient. Monocular visual impairment may be
accompanied by suppression of the more impaired eye and dominance
of the healthier eye. In current practice, the existence of
suppression is usually identified, but may not be quantified with
regard to the severity, by a clinician. Conditions in which
suppression is often observed may include binocular misalignment
conditions, anisometropic amblyopia, age-related macular
degeneration (AMD), glaucoma, or the like. Binocular misalignment
conditions may include strabismus, estropia, extropia, phoria,
convergence insufficiency, and the like. Failure of suppression in
such misalignment conditions may lead to diplopia, which is a
condition in which two images of the same object appear in
different locations. Alternatively, or additionally, failure of
suppression in misalignment conditions may result in confusion,
which is when images of different objects appear in the same
location. Diplopia and confusion may also be present as a result of
traumatic brain injury, as opposed to damage to a patient's eyes.
To minimize the occurrence of confusion, diplopia, or both, a
clinician may wish to encourage suppression. Current methods of
encouraging suppression include the use of an occluder, such as an
eye patch, to mask the image from one eye.
[0005] Amblyopia is an eye disorder commonly known as lazy eye and
is the most common cause of monocular visual loss among children.
Suppression is known to play a critical role in development of
amblyopia. Thus, a reliable and timely assessment of suppression is
believed to assist in detecting and treating amblyopia. The current
methods of assessing suppression include the Worth 4 dot test, the
use of Bagolini lenses, and OXO tests. However, none of the current
clinical methods are able to quantify the level of suppression.
[0006] The Worth 4 dot test, is also known as the Worth Lights
test. The Worth 4 dot test includes four circular lights presented
to a patient in a diamond formation using a flashlight. Red-green
anaglyphs are used to separate the images for each eye: the top red
dot is presented to the right eye through the red filter, and two
middle green dots are presented to the left eye through the green
filter. A white dot at the bottom of the diamond is presented to
both eyes. The bottom dot provides a fusional stimulus and is seen
as yellow if neither eye is suppressed in that location. In cases
where there is ocular dominance, or rivalrous alternation between
the eyes, the bottom dot will be perceived as red or green by the
patient. The patient is asked to report the number of dots he or
she sees, the colors of the dots, and the relative positions of the
dots at 40 cm near and 6 m far.
[0007] Bagolini lenses have fine striations that produce streaks
when a flashlight is viewed by a patient. The clinician
administering a test using Bagolini lenses places a first
45.degree. lens over one eye and a second 135.degree. lens over the
other eye of the patient. That is to say, that first lens causes a
stripe at a 45.degree. angle to be seen by the eye it covers, and
the second lens causes a stripe at 135.degree. angle to be seen by
the other eye, when the patient has normal binocular vision. When
the patient sees only one stripe, then the patient is determined to
have suppression of one eye.
[0008] The OXO test presents stripes, one above and one below the
"X" of an OXO panel. The patient looks at the panel with both eyes,
then each eye in turn while each eye is covered with polarizing
lenses. The patient reports the number and locations of strips at
40 cm and 1.5 m distance.
SUMMARY
[0009] Methods, systems, and apparatus, including computer program
products, are provided for quantification of inter-ocular
suppression in binocular vision or a patient.
[0010] In some example embodiments, a system for quantifying
suppression in binocular vision of a patient is disclosed. The
system may include a stimuli presentation device and a controller.
The stimuli presentation device may be configured to present
stimuli that include a distinct stimulus for each eye of the
patient. The controller is operably connected to the stimuli
presentation device and may include a computer, an adaptive
algorithm executed on the computer, and a stimulus generating
component. The computer may include an interface configured to
accept input from a clinician, a patient, or both. The adaptive
algorithm may be configured to accept a report describing what the
patient sees when presented with the stimuli and to calculate
adjustments to the stimuli to be presented in the next iteration of
stimuli. The stimulus generating component may be configured to
provide the next iteration of stimuli to the patient via the
stimuli presentation device.
[0011] The following features may be present in the system in any
suitable combination. The stimuli presentation device may include
3D stereo shutter glasses, anaglyph glasses, polarized lenses, a
Wheatstone stereogram, head mounted displays, lenticular screens,
or any combination thereof. In some embodiments, the system may be
configured to measure scale dependent suppression in the binocular
vision of the patient. In some such embodiments, the stimuli may
include bandpass filtered Sloan letters laid out in a manner
comprising multiple rows of letters, each row of decreasing letter
size, and each row having multiple letter, wherein each letter in a
row is distinct and having a different amount of contrast.
Additionally, each distinct stimulus for each eye of the patient
may have the same number of rows of letters and columns of letters,
in which a letter on a right eye stimulus corresponds to a letter
on a left eye stimulus in a similar position, and the corresponding
letters may have a combined contrast that is a fixed value. The
Sloan letters of the stimuli may include peak spatial-frequencies
of 0.5 to 10 cycles per degree in some embodiments. Alternatively,
or additionally, the Sloan letters may create a pattern that covers
a main area of a contrast sensitivity function in some embodiments.
The system may be configured to measure suppression in the
binocular vision of the patient while each eye of the patient is
fixated on a spot on the distinct stimulus presented to each eye.
In some embodiments, the system may be configured to measure both
visual-field and spatial-frequency dependent suppression in the
binocular vision of the patient. The stimuli may include numbers or
colored dots in some embodiments of the system.
[0012] In a related aspect, in some example embodiments a method is
disclosed that includes presenting stimuli to a patient, the
stimuli comprising a distinct stimulus for each eye of the patient;
accepting reports comprising observations from the patient
regarding the stimuli; creating an adjusted stimuli via an adaptive
algorithm executed on the computer controller, in which the
adaptive algorithm uses the reports as input; and presenting to the
patient the adjusted stimuli via a stimulus generating component of
the computer controller and the stimuli presentation device. The
stimulus presentation may be via a computer controller and a
stimuli presentation device. The reports may be accepted via the
computer controller.
[0013] The following features may be present in the method in any
suitable combination. The method may further include evaluating the
reports to determine whether suppression in binocular vision of the
patient can be quantified. Additionally, the method may include
quantifying suppression in binocular vision of the patient. The
stimuli can include bandpass filtered Sloan letters, numbers, or
colored dots in some embodiments. A stimulus for a right eye and a
stimulus for a left eye may include corresponding features, and the
features may include the bandpass filtered Sloan letters, numbers,
or colored dots. In such embodiments, each feature may have a
contrast value, in which a sum of the contrast values for
corresponding features equals a fixed amount, and the fixed amount
may be the same for each pair of corresponding features.
[0014] The above-noted aspects and features may be implemented in
systems, apparatus, methods, and/or articles depending on the
desired configuration. The details of one or more variations of the
subject matter described herein are set forth in the accompanying
drawings and the description below. Features and advantages of the
subject matter described herein will be apparent from the
description and drawings, and from the claims.
DESCRIPTION OF DRAWINGS
[0015] In the drawings,
[0016] FIG. 1A depicts an example of a system for measuring
suppression in the binocular vision of a patient, in accordance
with some example embodiments;
[0017] FIG. 1B depicts an example of a graph to determine a balance
point, in accordance with some example embodiments;
[0018] FIG. 2 depicts a block diagram of a process for measuring
suppression in the binocular vision of a patient, in accordance
with some example embodiments;
[0019] FIG. 3 depicts an example of a system for measuring
suppression in the binocular vision of patient, in accordance with
some example embodiments;
[0020] FIG. 4 depicts an example of a system for measuring both
visual-field and spatial-frequency dependent suppression in the
binocular vision of patient, in accordance with some example
embodiments;
[0021] FIG. 5 depicts an example of a system for measuring scale
dependent suppression in the binocular vision of patient that
employs numbers, in accordance with some example embodiments;
[0022] FIG. 6 depicts an example of a system for measuring scale
dependent suppression in the binocular vision of patient that
employs colored targets, in accordance with some example
embodiments;
[0023] FIG. 7 depicts examples of graphs showing proportion of weak
eye responses as a function of interocular contrast ratio and
spatial frequency, in accordance with some example embodiments;
and
[0024] FIG. 8 depicts an example of a graph of balance points as a
function spatial frequency for normal and amblyopic patients, in
accordance with some example embodiments.
[0025] Like labels are used to refer to same or similar items in
the drawings.
DETAILED DESCRIPTION
[0026] Currently available clinical tests provide only a rough idea
of presence of suppression. Although Bagolini test can be used to
quantify the level of suppression by placing a neutral density bar
in front of the non-suppressing eye until diplopia is reported by
the patient, these results depend on the patient's subjective
report of diplopia. Because of this drawback, it is rarely used.
Furthermore, this tests only measure suppression in central vision
and may not be easily modified to measure suppression outside the
fovea.
[0027] In some example embodiments, there is provided apparatus,
systems, and methods that provide quantification of inter-ocular
suppression in binocular vision impairment. Without in any way
limiting the claims, the apparatus, systems, and methods described
herein may provide a sensitive, quantitative assessment of
inter-ocular suppression. Some example embodiments may be capable
of measuring the magnitude of suppression on a fine spatial scale,
measuring the gradual changes in suppression, measuring foveal
and/or peripheral vision that may be affected by central or
peripheral eye disease, and/or measuring improvements in response
to treatment of the eye with a greater degree of vision loss. Thus,
these apparatus, systems, and methods can be used as a sensitive
diagnostic tool, as well as provide an estimate of the efficacy of
treatment outcomes, including surgical intervention to realign the
patient's eyes, and approaches to overcome suppression or diplopia,
such as traumatic brain injury therapies.
[0028] Interocular suppression may play a role in the etiology of
amblyopia. While amblyopic vision often lacks excitatory binocular
connections, such as binocular summation and stereopsis, the
inhibitory nature of binocular interactions such as interocular
suppression may remain persistent. This suppression may be
associated with the severity of amblyopic deficits. When
suppression is alleviated by equating the effective contrast of the
two eyes (for example, binocularly balanced stimuli), some
amblyopes may be able to achieve binocular fusion, which may
promote excitatory binocular connections such as binocular
summation. Treatment regimens designed to reduce suppression by
promoting an exposure to binocularly balanced stimuli which may
improve visual acuity and stereoacuity, while the residual and
recurrent amblyopia may be attributed to remaining binocular
imbalance. It may be possible to restore normal binocularity by
addressing the imbalance in monocular signals. Consequently,
assessment of interocular suppression may become increasingly
important in both the detection and treatment of amblyopia.
[0029] Core amblyopic deficits such as contrast sensitivity loss
and spatial distortion may exhibit spatial-frequency dependency.
For example, contrast sensitivity loss in amblyopia may be more
pronounced at mid-high spatial frequencies (SFs), while deficits at
low spatial frequencies are less common. Similarly, perceptual
distortion is more severe at higher spatial frequencies, with low
spatial frequencies being essentially perceived veridically. In
addition, gain control mechanisms may compensate for deficits at
detection threshold. The distinction between threshold and
supra-threshold contrast perception in amblyopia may raise
questions concerning the spatial frequency dependence of
interocular suppression. In some example embodiments, a
quantitative, clinically-viable process for assessing suppression
as a function of spatial frequency in amblyopia may be
provided.
[0030] To assess the effect of spatial frequency on suppression, a
series of dichoptic letter charts may be displayed to a patient in
a test. FIG. 1A depicts a system including a series of dichoptic
letter charts. In some example embodiments, the spatial frequency
of Sloan letters may be bandpass filtered in a layout similar to
the ETDRS acuity chart, which in this example includes four rows of
decreasing letter size by five columns of varying letter contrast
on a gray background. A different letter chart may be presented to
each eye of an observer via stereo-shutter glasses. At each
position, the identity and interocular contrast-ratio of the letter
on each chart may differ while the spatial frequency content of the
letter remains the same. The relative contrast of the letter in
each eye may be adjusted across several charts to determine the
balance point between the two eyes. The balance point may be
defined as the interocular contrast-ratio required for a patient to
see the letter in each eye with equal probability. In some example
embodiments the foregoing test may take less than seven
minutes.
[0031] FIG. 1A depicts an example of a system 100 including a
series of dichoptic letter charts for measuring scale dependent
suppression in the binocular vision of a patient. The system may
include a stimuli presentation device 110 and a controller 115. The
stimuli presentation device 110 may be 3D stereo shutter glasses,
anaglyph glasses, polarized lenses, Wheatsone stereogram, head
mounted displays, lenticular screens, or any other device that
suitably presents different images to each eye. The controller 115
may be a computer that accepts input from the patient or clinician
to present stimulus to the eyes of the patient 105 via a stimulus
generating component. Each eye receives different stimulus 120A/B,
130A/B. As shown in FIG. 1A, the first stimulus for the left eye
120A and the first stimulus for the right eye 130A include bandpass
filtered Sloan letters with peak spatial-frequencies of 0.5 to 10
cycles per degree. These patterns cover the main area of the
contrast sensitivity function. The letters are laid out on a gray
background, and the layout of the letters 123, 125, 127, 133, 135,
137 in the each stimulus is similar to the ETDRS acuity chart
(i.e., the chart developed as part of the Early Treatment for
Diabetic Retinopathy Study), with four rows of letters, each row of
decreasing letter size, and each row having five letters. Each
letter in a row has a different amount of contrast.
[0032] Each eye may be presented with a different stimulus via the
stimuli presentation device 110, which in FIG. 1A is a pair of
computer-controlled 3D stereo shutter glasses. At each position,
the identity and inter-ocular contrast-ratio of the letter on each
chart differs while the spatial-frequency content of the letter
remains the same. The patient is instructed either by the clinician
or the controller 115 to read aloud the chart in top-to-bottom and
left-to-right order, reporting the identity of the letters, while
using his or her foveal vision. No letters are repeated on each
line, so the identity of each letter is unique, and in this way,
suppression and diplopia can be detected from repetitions and
confusions.
[0033] On each stimulus 120A/B, 130A/B, the combined contrast of
both letters is fixed. That is to say, the sum of the contrast of
the letter in the upper left-hand corner 123 of the chart for the
left eye 120A and the letter in the upper left-hand corner 133 of
the chart for the right eye 130A is the same as the sum of the
first letters 125, 135 of the second rows and of the third row 127,
137. A patient with normal sight perceives the letter with higher
contrast. When the effective contrast of the letter presented to
each eye is balanced, each letter is reported with equal frequency.
As the patient reports what he or she perceives, the controller 115
adjusts the inter-ocular contrast ratio to iteratively determine
the presence and degree of suppression. For patients with normal
vision, the balance point when the letter shown to the left eye and
that shown to the right eye are perceived equally typically occurs
when the inter-ocular contrast ratio is close to 0.5. Suppression
is quantified as the contrast ratio at this balance point. As
mentioned above, on successive charts, the interocular contrast
ratios on each line are adaptively updated by an algorithm to
determine the ratio at which the letter in each eye is reported
with equal probability. This process yields the estimation of
suppression for each spatial frequency. It may be after about 10
charts are read by the patient that a reliable estimate of
suppression at multiple spatial frequencies is reached.
[0034] In some example embodiments, ten letters of the alphabet in
Sloan font may be used by the system in FIG. 1A to measure
suppression. Other fonts and numbers of letters may be used as
well. Test letters may be spatially bandpass filtered with a cosine
log filter with peak object spatial frequency of 3 cycles per
letter (c/letter). The filter may have a bandwidth (full-width at
half-height) of 1-octave and may be radially symmetrical in the
log-frequency domain. In some example embodiments, the retinal
spatial frequency of the test letters may range between 0.5 to 5
cycles per degree (c/deg) at a viewing distance of 57 cm. In some
example embodiments, the retinal spatial frequency may be achieved
by fixing the object spatial frequency at 3 cycles/letter and
varying the image sizes determined by an angular size such as
0.6.degree., 1.2.degree., 2.degree., and 6.degree.. Other angular
sizes may be used as well. A spatial frequency of 3 c/letter may be
in a rage of optimal spatial-frequency size between 1 and 7
c/letter depending on angular letter size.
[0035] Test letters may be displayed on a uniform gray background
(60 cd/m.sup.2) with varying contrasts such as Michelson contrasts.
The stimuli may be generated and controlled by controller 115 that
may include a computer. For example, a personal computer may
control the stimuli. The personal computer may use software such as
MATLAB that may include a psychophysics toolbox extension. Stimuli
may be presented on a liquid crystal display monitor. For example,
a computer display may be used such as an Asus VS278H-E having a
refresh rate of 144 Hz and a resolution of 1920.times.1080 and
brightness of 250 cd/m.sup.2. Stimuli may be rendered with
grayscale levels using a bit-stealing method. The monitor may be
calibrated using a spectrophotometer such as a Photo Research
SpectraScan 655 and may be linearized. Stereo-shutter glasses may
be used by patients/subjects. For example, nVidia Corp.
stereo-shutter glasses may be used. In some example embodiments,
stereo-shutter may have a frame rate 72 Hz per eye. Other frame
rates may also be used.
[0036] As shown in FIG. 1A, the letters may be arranged in a layout
similar to the ETDRS acuity chart with four rows of decreasing
letter size and five columns of varying contrast. A different
letter chart may be presented via stereo-shutter glasses to the
weak eye compared to the strong eye. At each letter position on
each chart, the identity and interocular contrast-ratio of the
letter on each chart may differ while the spatial frequency content
of the letter remains the same. The sum of the interocular contrast
ratio across the two eyes may be fixed at 100% contrast or any
other contrast value. For example, when using a 100% contrast
value, the contrast in the weak eye may be 70%, and the contrast in
the strong eye may be 30% or vice versa. To minimize participant
confusion, the same letter may not appear twice in the same row. In
some example embodiments, the interocular contrast ratio may be
randomized across five letter slots in each row to avoid any
ascending or descending pattern of contrast arrangement, which may
potentially bias a participant's response.
[0037] Participants may read aloud the letters in the chart from
top-to-bottom and left-to-right order as quickly and accurately as
possible with unconstrained eye movements. In case participants
experience binocular rivalry, they may be instructed to report the
more dominant percept. Participants may be encouraged to report
their percept as quickly as possible in order to minimize binocular
rivalry. Their responses may be recorded. Completion of the first
chart may cause a second chart that may be followed by subsequent
charts. The relative contrast of the letter in each eye may be
determined via an adaptive procedure. For example, for a given
chart, the proportion of correct recognition may be determined at
each interocular contrast ratio (each letter slot, 5 slots per
line), which may be used to estimate the balance point (BP) between
the two eyes for each spatial frequency (each line in the chart).
The balance point may be defined as the interocular contrast-ratio
yielding letter recognition in each eye with equal (50%) or nearly
equal probability. The balance point may be updated after each
letter chart based on the results from the most recent letter chart
and the previously tested letter charts. The updated balance point
may be used to determine the range of contrast ratios for a
subsequent chart. In this way, over several charts, the range of
interocular contrast-ratio may converge to a balance point. On
successive letter charts, the testing points may be adjusted to be
closer to the estimated balance point. The updating process may be
an adaptive process. In some example embodiments, the balance
points may be computed for each spatial frequency arranged in each
row. In some example embodiments, participants may be given a one
or more practice tests before a test to determine the balance point
is performed. A testing session may last 7 minutes or less.
[0038] In some example embodiments consistent with FIG. 1A, letters
that are bandpass filtered may be used as test stimuli. For
example, letters in a Sloan font may be filtered to produce peak
spatial-frequencies of 0.5 to 5 cycles per degree. Letters may be
arranged in a layout similar to the ETDRS acuity chart including
four rows of decreasing letter size by five columns of varying
letter contrast on a gray background. Each row may contain a single
spatial frequency of test letters such as 0.5, 1.5, 2.5, and 5.0
c/deg. Each slot may contain a different interocular contrast
ratio. A different letter chart may be presented to each eye via
stereo-shutter glasses. At each letter slot, the identity and
interocular contrast-ratio of the letter on each chart may differ
while the spatial-frequency content of the letter may remain the
same. Participants may read the chart in left-to-right and
top-to-bottom order. The relative contrast of the letter in each
eye may be adjusted across several charts to determine the
interocular balance point (BP). The balance point may be defined as
the interocular contrast-ratio required for participants to report
the letter in each eye with equal probability (0.5 proportion
responses for the letter presented to the weak eye).
[0039] FIG. 1B depicts a chart for determining a balance point, in
accordance with some example embodiments. For example, a
psychometric function may be used in the determination of a balance
point between the proportion of participant responses from a weak
eye and an interocular contrast ratio of the weak eye. Data
corresponding to the strong eye responses may be the mirror
reversal of the data from the weak eye because the proportion of
strong eye responses may equal one minus the proportion of weak eye
responses. A test of a participant may determine the proportion of
weak eye responses as a function of interocular contrast ratio. In
some example embodiments, the resulting data may be fit to a
Weibull function to derive a balance point yielding 50%
identification for each eye. See, for example, the black dashed
line 140 in FIG. 1B. Curves 142 and 144 represent proportions of
weak eye responses as a function of interocular contrast ratio for
different participants. Curve 142 represents data from a normally
sighted patient/participant whose binocular vision is well
balanced. As such, their balance point (x-axis value in FIG. 1B) is
close to a value of 0.5 at 142A. In some example embodiments, the
balance point may correspond to an interocular contrast ratio
(x-axis in FIG. 1B) that corresponds to 50% of responses (y-axis in
FIG. 1B) from the patient's weak eye. Curve 144 corresponds to a
participant whose weak eye is suppressed, resulting in a balance
point that is higher than 0.5. For example, FIG. 1B at 144A shows a
participant with a balance point of approximately 0.7.
[0040] In some example embodiments, data containing a participant's
letter recognition at varying contrast ratios may be collected in
accordance with the foregoing. A balance point may be determined
from the data by fitting the psychometric function to the data.
Psychometric functions of percent correct versus interocular
contrast ratio of the weak eye may be created by fitting the data
with Weibull functions as shown in FIG. 1B. A curve fit may be
determined for a participant using a search method. For example, a
simplex search method may be used to minimize the weighted residual
sum of squares. Other searches may also be used. In some example
embodiments, the reciprocal of the variance of each data point
(1/.sigma..sup.2) may be used to weight in the curve fit. The
balance point may be based on the estimated 50% correct point on
the psychometric function for each spatial frequency. For example,
the balance point of 0.5 may indicate 50% contrast in the weak eye
matches 50% contrast in the strong eye (FIG. 1B at 142, 142A),
suggesting that both eyes are well balanced. On the other hand, a
balance point of 0.8 means that 80% contrast in the weak eye
matches 20% contrast in the strong eye. Thus, the larger the
balance point depicted in a rightward shift of the psychometric
function, the more attenuated or suppressed the input signal of the
weak eye may be. For example, a shift from curve 142 to curve 144
as shown in FIG. 1B.
[0041] FIG. 2 depicts a block diagram of an example of a process
200 for measuring suppression in the binocular vision of a patient.
At the start of assessment for suppression, a clinician fits a
patient with a computer-controlled stimuli presentation device, as
in 205. As mentioned above, the computer-controlled stimuli
presentation device may be 3D stereo shutter glasses, anaglyph
glasses, polarized lenses, Wheatsone stereogram, head mounted
displays, lenticular screens, or any other device or method that
suitably presents different images to each eye. Once the patient is
properly fitted, the clinician, in 210, presents slightly different
stimuli to each eye of patient using computer-controlled stimuli
presentation device. Then, in 215, the clinician asks the patient
to report the stimulus observed. The patient reports what he or she
observed using his or her binocular vision. These observations
(e.g., reports) are provided to the controller so that an adaptive
algorithm that is executed on the computer-controller may adjust
the stimulus to present to the patient, and new stimuli are
presented iteratively, in 220. The adaptive algorithm adjusts the
stimulus, in 225, in response to the patient's observations until
an estimate of the degree of suppression can be made by the
clinician or computer-controller. The number of iterations is about
10 iterations of adjusting the stimulus until suppression can be
assessed by the controller or the clinician.
[0042] FIG. 3 depicts an example of a system 300 for measuring
suppression in the binocular vision of patient. The system 300 is
similar to that shown in FIG. 1A with a stimuli presentation device
110 that is placed before the patient's eyes 105, and a controller
115 that determines what is presented to the patient. The stimulus
presented to the left eye 320 and to the right eye 330, includes
Sloan letters in which the combined contrast of both letters is
fixed and controlled by a computer associated with the controller.
The difference is that the system shown in FIG. 3 measures regional
suppression across the patient's visual field. The letters are
arranged across the visual field to test suppression at different
visual field locations. The visual field areas may be informed by
extrinsic information, such as suspected diagnosis, retinal imaging
data, subjective patient reports or questionnaires, and the like.
Visual field areas can include about 10, 24, or 30 degrees
diameter, which are similar to about 10-2, 24-2, or 30-2 Humphrey
Visual Fields.
[0043] The patient reports to the clinician or the controller the
letter identified as he or she reads from left to right, starting
at the top row. The patient reads the letters while fixating the
central letter 340A, 340B. Fixation is confirmed by eye-tracking
technology. The inter-ocular contrasts across each position of the
chart serve to sample different ratios to determine which eye
perceives the letter at each ratio. As the controller presents
charts in response to the patient's reports via a stimulus
generating component and the stimuli presentation device 110, the
inter-ocular contrast ratio of each letter is adaptively updated to
determine the ratio at which the letter in each eye is reported
with equal probability at each location. Thus, suppression is
measured separately for each retinal location. To measure visual
field suppression at different spatial frequency scales, the
stimulus chart can be reproduced with bandpass filtered letters but
at a different spatial frequency, and low (e.g., 0.5 c/deg) to high
(12 c/deg) spatial frequencies, following the contrast sensitivity
function.
[0044] FIG. 4 depicts an example of a system 400 for measuring both
visual-field and spatial-frequency dependent suppression in the
binocular vision of a patient. As with the systems of FIG. 1A and
FIG. 3, the system 400 of FIG. 4 has a stimuli presentation device
110 that is placed before the patient's eyes 105, and a controller
115 that determines what is presented to the patient. The system of
FIG. 4 may assess both visual-field and spatial frequency dependent
suppression. In FIG. 4, the stimuli 420, 430 includes wide-field
sinusoidal gratings with spatial-frequencies with diameters and
spatial frequencies that may vary for each patient. Values for the
diameter can include about 30 degrees (e.g., about 30-2 Humphrey
Visual Field) and low (0.5 c/deg) to high (10 c/deg) spatial
frequencies, following the contrast sensitivity function.
[0045] Each of the patient's eyes 105 is presented with an
identical wide-field grating via the stimuli presentation device
that is a pair of stereo-shutter glasses. Each iteration of stimuli
presentation includes a localized contrast increment 445 that is
applied to one of the eyes. In FIG. 4, the localized contrast
increment 445, or test patch, is shown applied to the stimulus of
the right eye 430. The size of the test patch 445 may vary
according to the test location, the disease diagnosis, or upon
extrinsic data such as retinal images or patient's answers to one
or more questionnaires. Each test patch 445 is assessed in a random
order. The patient's eyes 105 are fixated on central points 440A,
440B while he or she describes the presence of the test patch 445.
Fixation of the patient's eyes 105 is confirmed by eye-tracking
technology. The patient's descriptions are recorded by the
clinician on a computer associated with the controller 115 or
recorded directly by the controller 115, and inter-ocular threshold
differences are accumulated across multiple iterations to determine
spatial-frequency and visual-field dependent suppression
thresholds.
[0046] In some example embodiments, an identical or nearly
identical vertical grating, subtending 28 degrees of visual angle
may be presented to the weak and strong eyes of an participant via
3D shutter glasses. The target patch may include a contrast
increment (.DELTA.C) at 445 that may be presented to one of the
eyes in random order. On a given trial, the target patch may appear
in one of the two eyes and at one of 28 locations in the visual
field in random order. Contrast-increment thresholds may be
measured with a method of adjustment. The participant may be
instructed to fixate on a central dot. The contrast may be
increased until the central dot becomes distinguishable form the
background. In some example embodiments, the contrast may be
adjusted by the participant by using the up and down arrow keys on
a computer keyboard or by using another computer input device.
[0047] In some example embodiments, the test stimulus may be a
vertical sinusoidal grating (subtending 28 degrees of visual angle)
with spatial frequency lying within a particular range. For
example, the spatial frequency may be between 0.5 and 5 cycles per
degree (cpd) at a viewing distance of 57 cm. The base contrast of
the stimulus may be fixed at, for example, 30% while a contrast
increment (.DELTA.C) may be applied to a circular patch (target
patch). The target patch may be presented in one of 28 locations in
the grating. An example target location is shown in FIG. 4 at 445.
In some example embodiments, the size of the target patch may be
2.degree. (.ltoreq.4.5.degree. eccentricity), 2.5.degree.
(4.5.degree.<x.ltoreq.8.25.degree. eccentricity) and/or
3.degree. (8.25.degree.<x.ltoreq.13.degree. eccentricity) in
diameter depending on the eccentricity of the target location in
the visual field with respect to the fovea, indicated by the black
fixation dot 440A/440B in FIG. 4.
[0048] In some example embodiments, suppression may be defined as a
difference in contrast-increment thresholds between the two eyes
when a contrast increment (.DELTA.C) is presented to one of the
eyes while an identical stimulus with a pedestal contrast (C) was
presented to both eyes. In the example of FIG. 4, an identical
vertical pedestal grating may be presented to the weak and strong
eyes of an observer via the 3D shutter glasses while a target patch
containing a contrast increment (.DELTA.C) may be presented only to
one eye. For a given trial, the target patch may appear in one of
the two eyes and at one of 28 locations in the visual field. The
arrangement of the target locations may be circular and symmetric
with respect to the origin. In some example embodiments, there may
be 12 locations for the target patch in the visual field where
eccentricity is equal to or less than 4.5.degree., and 16 locations
of which eccentricity is greater than 4.5.degree. and equal to or
less than 13.degree.. The target locations may be approximately
evenly distributed across the visual field and adjusted in size, to
respect cortical magnification. The presentation sequence of the
target in each eye and visual field location may be randomized
across trials. In this way, the participant may not know which eye
or test location for the next target. Data for the two spatial
frequencies (0.5 and 5 c/deg) may be collected in different runs,
in random order across participants. Other spatial frequencies,
target patch shapes, target patch locations, target patch angular
range, and/or target patch sizes may also be used.
[0049] FIGS. 5 and 6 depict systems for measuring suppression in
patients who may not be able to identify letters in stimuli. FIG. 5
depicts an example of a system 500 for measuring scale dependent
suppression in the binocular vision of patient that employs stimuli
520, 530 with bandpass filtered numbers 523, 527, 533, 537. In FIG.
5 the interocular ratio of contrast is adjusted by the controller
115 based on the reports of the patient. In this manner, the system
500 finds the effective level that causes the patient to report the
number in each eye with equal frequency.
[0050] FIG. 6 depicts an example of a system 600 for measuring
scale dependent suppression in the binocular vision of patient that
employs stimuli 620, 630 with colored targets 624, 634. Although
FIG. 6 shows targets 624, 634 as shaded gray, the targets may be
colored. For example, targets 624 may be green, and/or targets 634
may be red. Targets 624, 634 may also be any other color as well.
Each spot of color in the stimuli 620, 630 of the system 600 shown
in FIG. 6 is adjusted by the controller 115 until the patient
reports the color of each eye with equal frequency.
[0051] FIG. 7 depicts example responses consistent with reliance on
the weaker eye ("weak eye responses") that are plotted against
interocular contrast ratio. Each row in FIG. 7 shows data from an
individual participant. Each graph in FIG. 7 shows a proportion of
weak eye responses as a function of interocular contrast ratio.
Each graph corresponds to a spatial frequency with the graphs
arranged from lower spatial frequency to higher spatial frequency
for each row from left to right. The top row 710 corresponds to a
participant with normal vision and the bottom three rows 720A,
720B, 720C correspond to three participants with amblyopia. Each
column corresponds to a different spatial frequency from 0.5, 1.5,
2.5 and 5 c/deg. In some example embodiments, the balance point may
be determined by fitting the data using a Weibull function and
finding the contrast ratio corresponding to 0.5 proportion of weak
eye responses. In some example embodiments, the above described
model may fit with r2 values of 0.989 to 0.999 (mean
0.994.+-.0.003), indicating that about 99% of variance is accounted
for by the model.
[0052] In the example of FIG. 7, the solid lines in each graph in
rows 710, 720A-C show the best fit of the data to the forgoing
process. The dotted arrow lines indicate the determined balance
points. Row 710 corresponds to a participant with normal vision.
Row 720A corresponds to a participant with strabismic amblyopia.
Row 720B corresponds to a participant with anisometropic amblyopia.
Row 710 corresponds to a participant with anisometropic
amblyopia.
[0053] In some example embodiments, the balance points of
participants with amblyopia may increase with increasing spatial
frequency. For example, the balance point may increase with
increasing frequency as represented by a rightward shift of the
psychometric function. For example, the balance point of the weak
eye at row 720A increased from 0.69 at 0.5 c/deg. to 0.92 at 5
c/deg. This may indicate, for example, that for a low spatial
frequency, 69% contrast is required for the weak eye to match 31%
contrast in the strong eye while for a high spatial frequency 92%
of contrast is needed for the weak eye to match 8% contrast in the
strong eye. This substantially higher balance point may be observed
in participants with amblyopia suggesting that input from the weak
eye is attenuated or suppressed by the strong eye under conditions
of suprathreshold perception. The suppression may be more
pronounced at higher spatial frequencies. The balance points of
normally sighted observers may be close to a value of 0.5,
indicating that the input signals from the two eyes may be treated
approximately equally and in a manner that is largely independent
of spatial frequency.
[0054] In accordance with some example embodiments, FIG. 8 depicts
mean balance points as a function of spatial frequency for
participants with amblyopia 820 and normal vision 810. The dotted
line 830 indicates a proportion of weak-eye responses equal to 0.5,
indicating balanced contrast perception between the two eyes, i.e.
no interocular suppression. Consistent with individual data (see,
for example, FIG. 7), across spatial frequencies the balance points
for the amblyopic group (0.80.+-.0.02) may be higher than for the
normal control group (0.55.+-.0.01). Error bars in FIG. 8 represent
.+-.1 Standard Errors of the Mean (SEM).
[0055] Although some of the drawings show examples of results,
other results may be obtained as well.
[0056] A two-way repeated measures ANOVA may support a significant
main effect of subject group (F.sub.(3, 30)=3.48, p=0.028) on
balance point. Balance points of an amblyopia group may differ
across different spatial frequencies (F.sub.(3, 12)=6.26, p=0.008)
while that of a normal group may remain constant across different
spatial frequencies (F.sub.(3, 18)=0.62, p=0.601). Tukey's HSD
pairwise comparison test may further reveal that the balance point
of the spatial frequency of 0.5 c/deg. may be different from either
that of 2.5 or 5 c/deg. (all p<0.01), which may suggest that the
balance point increases with spatial frequency in amblyopic
observers. The average balance point of the normal control group
(0.55.+-.0.01) may be significantly different from a value of 0.5
(t.sub.(6)=5.93, p=0.001), which may indicate mild eye dominance in
normally-sighted individuals.
[0057] The subject matter described herein may be embodied in
systems, apparatus, methods, and/or articles depending on the
desired configuration. For example, the controllers of a system for
quantifying inter-ocular suppression in binocular vision impairment
(or one or more components therein) and/or the processes described
herein can be implemented using one or more of the following: a
processor executing program code, an application-specific
integrated circuit (ASIC), a digital signal processor (DSP), an
embedded processor, a field programmable gate array (FPGA), and/or
combinations thereof. These various implementations may include
implementation in one or more computer programs that are executable
and/or interpretable on a programmable system including at least
one programmable processor, which may be special or general
purpose, coupled to receive data and instructions from, and to
transmit data and instructions to, a storage system, at least one
input device, and at least one output device. These computer
programs (also known as programs, software, software applications,
applications, components, program code, or code) include machine
instructions for a programmable processor, and may be implemented
in a high-level procedural and/or object-oriented programming
language, and/or in assembly/machine language. As used herein, the
phrase "machine-readable medium" refers to any computer program
product, computer-readable medium, apparatus and/or device (e.g.,
magnetic discs, optical disks, memory, Programmable Logic Devices
(PLDs)) used to provide machine instructions and/or data to a
programmable processor, including a machine-readable medium that
receives machine instructions. Similarly, systems are also
described herein that may include a processor and a memory coupled
to the processor. The memory may include one or more programs that
cause the processor to perform one or more of the operations
described herein.
[0058] Although a few variations have been described in detail
above, other modifications or additions are possible. In
particular, further features and/or variations may be provided in
addition to those set forth herein. For example, the
implementations described above may be directed to various
combinations and subcombinations of the disclosed features and/or
combinations and subcombinations of several further features
disclosed above. In addition, the logic flow depicted in the
accompanying figures and/or described herein does not require the
particular order shown, or sequential order, to achieve desirable
results. In various example implementations, the methods (or
processes) can be accomplished on mobile station/mobile device side
or on the server side or in any shared way between server and user
equipment/mobile device with actions being performed on both sides.
The phrases "based on" and "based on at least" are used
interchangeably herein. Other implementations may be within the
scope of the following claims.
* * * * *