Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SYSTEMS AND METHODS FOR MAPPING AND EVALUATING VISUAL
DISTORTIONS
Technical Field
[0001] The present disclosure relates to systems and methods for mapping and
evaluating
visual distortions, and in particular to systems and methods for mapping and
evaluating visual
distortions caused by metamorphopsia.
Background
[0002] Visual perception is a complex process in which light passes through
the cornea, lens,
and various humours of the eye before being received by the retina where it is
detected by
photoreceptors. Nervous signals generated by these photoreceptors are
processed by the
brain, and more particularly by the visual cortex. A substantial portion of
what we perceive as
vision is provided by the cognitive processing of the visual cortex. This
cognitive processing
is not fully developed at birth and must be "learned" during the developmental
stages of the
visual system (i.e. in the early years of sight). Such cognitive processing
includes, for
example, mapping stimuli received at particular points of the retina into
points of a coherent
image. For instance, after cognitive processing, the images of both eyes are
perceived as
being in registration, inverted images on the retina are perceived as being
non-inverted,
straight lines are perceived as straight rather than curved (despite the
retina itself being
curved), and so on.
[0003] Metamorphopsia is a condition in which a portion of the retina is
displaced relative to
its original placement (i.e. its placement during the developmental stages of
the visual
system). The associated cognitive processing does not generally fully adapt to
this
displacement, resulting in distortions in the visual perception of images
received by the
retina. For example, images perceived by a subject with metamorphopsia may be
skewed, of
a different size, in a different location, or otherwise different than the
same images perceived
by a subject with a normal retina.
[0004] Metamorphopsia has a variety of causes, the most common of which is age-
related
macular degeneration (AMD). Although there is not currently a cure for AMD,
there are a
variety of treatments which can slow (or even temporarily reverse) its
progression. Such
treatments include photodynamic therapy, ocular injections of anti-vascular
endothelial
growth factor, and nutritional supplements such as lutein, meso-zeaxanthin and
zeaxanthin.
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Accordingly, there is a general desire to detect metamorphopsia in subjects at
an early stage.
Further, there is a general desire to evaluate the severity of particular
cases of
metamorphopsia in order to assess the efficacy of a particular treatment.
[0005] The quality of life of a subject may be severely and adversely impacted
by
metamorphopsia (e.g. by a progressively worsening inability to perform daily
tasks such as
driving, reading, recognizing faces, etc.). Accordingly, it is particularly
advantageous in
many circumstances to determine the severity of the visual distortions
perceived by the
subject. The severity of visual distortions may often not be directly
determinable from the
severity of the physiological displacement of the affected portion of the
retina (e.g. as
measured via optical coherence tomography), due to the complexities of the
cognitive
processes discussed above.
100061 Detection of metamorphopsia and the subsequent measurement of the
efficacy of
treatments are commonly performed by presenting subjects with an Amsler grid,
such as the
example Amsler grid 100 shown in Figure 1. Subjects fixate one eye on fixation
target 102
and provide anecdotal feedback on, among other things, the size and location
of distortions in
grid lines 104. This approach can present challenges in ensuring that results
are comparable
between assessments, since even small variations in the subject's viewing
distance, the
subject's fixation point, and/or other viewing conditions may significantly
impact the
perceived size and location of distortions. Further, measurement by
conventional Amsler grid
may be relatively imprecise.
100071 There have been several recent attempts to collect more precise
measurements of
visual distortions for the purpose of quantifying, mapping, and (ultimately)
correcting the
distortions. Some such developments are disclosed, for example, in US Patent
Nos.
5,589,897, 5,892,570, and 8,708,495. Such attempts generally involve providing
a pattern
which is adjustable by the subject. The subject may then adjust the pattern
until it appears
"correct" (e.g. until the grid lines of Amsler grid 100 appear straight).
100081 Due to the complexity of the visual system, existing methods may still
be prone to
inaccuracies, inefficiencies, and/or imprecision in certain circumstances.
Accordingly, there
is a general desire for systems and methods for mapping and evaluating visual
distortions
caused by metamorphopsia which ameliorate at least some of the deficiencies
discussed
above and/or other deficiencies.
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100091 The foregoing examples of the related art and limitations related
thereto are intended
to be illustrative and not exclusive. Other limitations of the related art
will become apparent
to those of skill in the art upon a reading of the specification and a study
of the drawings.
Summary
[0010] The following embodiments and aspects thereof are described and
illustrated in
conjunction with systems, tools and methods which are meant to be exemplary
and
illustrative, not limiting in scope. In various embodiments, one or more of
the above-
described problems have been reduced or eliminated, while other embodiments
are directed
to other improvements.
[0011] An aspect of the present disclosure provides a method for mapping
visual distortions
perceived by a subject. The method may be performed by a processor in
communication with
a display. The method includes displaying, at the display, a fixation target
to the subject. The
method includes receiving, at the processor, an indication corresponding to an
identification
of a distortion region by the subject. The distortion region has a location
determined relative
to the fixation target. The method includes displaying, at the display, an
adjustable reference
pattern to the subject. The adjustable reference pattern is at least partially
within the
distortion region and the adjustable reference pattern is adjustable within
the distortion region
and fixed outside the distortion region. The method includes receiving, at the
processor, an
indication corresponding to an adjustment by the subject of the adjustable
reference pattern
within the distortion region. The adjustment is at least partially
complementary to visual
distortion perceived by the subject in the distortion region. The method
includes determining,
at the processor, a fixed reference pattern based on the adjustment of the
adjustable reference
pattern.
100121 The method further includes displaying, at the display, one or more
adjustable
patterns to the subject. Each of the one or more adjustable patterns is at
least partially within
the distortion region, and each of the one or more adjustable patterns is
adjustable within the
distortion region and fixed outside the distortion region. The method further
includes
receiving, at the processor, one or more indications corresponding to one or
more adjustments
by the subject of the one or more adjustable patterns within the distortion
region. The one or
more adjustments are at least partially complementary to visual distortion
perceived by the
subject in the distortion region. The method further includes determining, at
the processor, a
distortion map based on the one or more adjustments of the one or more
adjustable patterns.
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[0013] An aspect of the present disclosure provides systems for performing the
methods
described above. Systems according to particular embodiments may comprise a
processor
configured to perform one or more of the methods described herein. Non-
transitory
computer-readable media may be provided with instructions, which (when
executed by a
suitably configured processor), cause the processor to perform one or more of
the methods
described herein.
[0014] According to another aspect of the invention, the methods described
herein are
encoded on computer readable media and which contain instructions executable
by a
processor to cause the processor to perform one or more of the methods
described herein.
[0015] According to another aspect of the invention, systems are provided
wherein
processors are configured to perform one or more of the methods described
herein.
[0016] Further aspects of the invention and features of example embodiments
are illustrated
in the accompanying drawings and/or described in the following description.
Brief Description of the Drawings
[0017] The accompanying drawings illustrate non-limiting example embodiments
of the
invention.
[0018] Figure 1 is an example of a prior art Amsler grid.
[0019] Figure 2A is a schematic cross-sectional illustration of an eye.
[0020] Figure 2B is a graph of visual acuity (on the vertical axis) against
retinal eccentricity
(on the horizontal axis).
[0021] Figure 2C is a photograph of a portion of the macular region of an
example retina.
[0022] Figure 2D is a photograph of a portion of the peripheral region of an
example retina.
[0023] Figure 3A is an illustration of an example image received on an example
normal
retina.
[0024] Figure 3B is an illustration of an example perception of the image of
Figure 3A by an
example subject with a normal retina.
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[0025] Figure 4A is an illustration of an example image received on an example
retina with
metamorphopsia.
[0026] Figure 4B is an illustration of an example perception of the image of
Figure 4A by an
example subject with a retina with metamorphopsia.
[0027] Figure 5A is an illustration of an example perception of an example
image which has
been corrected to account for the subject's reported visual distortions,
wherein the perception
comprises double vision.
[0028] Figure 5B is an illustration of an example perception of an example
image which has
been corrected to account for the subject's reported visual distortions,
wherein the perception
comprises an uncorrected portion.
[0029] Figure 5C is an illustration of an example perception of an example
image which has
been corrected to account for the subject's reported visual distortions,
wherein the perception
is skewed.
[0030] Figure 6A is an illustration of an example corrected image received on
the example
retina of Figure 4A.
[0031] Figure 6B is an illustration of an example perception of the image of
Figure 6A by the
example subject of Figure 4B.
[0032] Figure 7 is a block diagram illustrating an example method for mapping
visual
distortions.
[0033] Figure 8A is a schematic side elevation view of an example system for
mapping
visual distortions.
[0034] Figure 8B is a schematic plan view of the system of Figure 8A.
[0035] Figure 9A is an example calibration display prior to a subject's
placement of
boundary lines.
100361 Figure 9B is the example perception of a calibration display of Figure
9A during the
subject's placement of an example first boundary line.
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[0037] Figure 9C is the example calibration display of Figure 9A after the
subject's
placement of example first and second boundary lines.
[0038] Figure 9D is the example perception of a calibration display of Figure
9A during the
subject's placement of an example third boundary line.
[0039] Figure 9E is the example calibration display of Figure 9A after the
subject's
placement of example third and fourth boundary lines.
[0040] Figure 9F is the example perception of a calibration display of Figure
9A during the
subject's placement of an example fifth boundary line.
[0041] Figure 9G is the example calibration display of Figure 9A after the
subject's
placement of example fifth and sixth boundary lines.
[0042] Figure 9H is the example perception of a calibration display of Figure
9A during the
subject's placement of an example seventh boundary line.
[0043] Figure 91 is the example calibration display of Figure 9A after the
subject's placement
of example seventh and eighth boundary lines.
[0044] Figure 9J is the example calibration display of Figure 9A after
placement of eight
example boundary lines and depicting an example region defined therebetween.
[0045] Figure 9K is the example calibration display of Figure 9A after
placement of eight
example boundary lines and depicting another example region defined
therebetween.
[0046] Figure 9L is the example calibration display of Figure 9A after a
subject's
identification of a distortion region according to an alternative embodiment.
[0047] Figure 10A is a grid illustrating various example resolution regions
according to an
example embodiment.
[0048] Figure 10B depicts various example adjustment rows according to the
resolution
regions of Figure 10A.
[0049] Figure 11A is an example adjustment display prior to a subject's
adjustment of an
example adjustment row.
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[0050] Figure 11B is the example adjustment display of Figure 11A after
adjustment of the
example adjustment row of Figure 11A.
[0051] Figure 11C is the example adjustment display of Figure 11A prior to a
subject's
adjustment of an example adjustment column.
[0052] Figure 11D is the example adjustment display of Figure 11A after
adjustment of the
example adjustment column of Figure 11C.
[0053] Figure 11E is an example display of an example visual reference based
on the
adjustment row of Figure 11B and adjustment column of Figure 11C.
[0054] Figure 11F is an illustration of an example perception of the display
of Figure 11E by
an example subject with a retina with metamorphopsia.
[0055] Figure 12A is an example adjustment display comprising the example
visual reference
of Figure 11E prior to a subject's adjustment of a further example adjustment
row.
[0056] Figure 12B is an example adjustment display comprising the example
visual reference
of Figure 11E after the subject's adjustment of the further example adjustment
row of Figure
12A.
[0057] Figure 13A is an example verification pattern according to an example
embodiment.
[0058] Figure 13B is the example verification pattern of Figure 13A rotated by
approximately 450
.
[0059] Figure 14A is an example selection display showing a user selection of
a distorted
region.
[0060] Figure 14B is an example refinement display showing a constrained
region for further
adjustment based on the user selection of Figure 14A.
100611 Figure 14C is an example perception of the example refinement display
of Figure
14B.
[0062] Figure 15A is an example perception map or distortion map illustrated
with distorted
gridlines in an example distortion region.
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[0063] Figure 15B is an expanded view of a portion of the example map of
Figure 15A
illustrating an example method for determining a severity of displacement
based on an area
displaced.
[0064] Figure 15C is an expanded view of a portion of the example map of
Figure 15A
illustrating an example method for determining a severity of displacement
based on the
displacement of a point from its original (pre-distortion) position.
[0065] Figure 15D is an expanded view of a portion of the example map of
Figure 15A
illustrating an example method for determining a severity of displacement
based on the local
change in displacement of a point.
Detailed Description
[0066] Throughout the following description, specific details are set forth in
order to provide
a more thorough understanding of the invention. However, the invention may be
practiced
without these particulars. In other instances, well known elements have not
been shown or
described in detail to avoid unnecessarily obscuring the invention.
Accordingly, the
specification and drawings are to be regarded in an illustrative, rather than
a restrictive sense.
[0067] Methods described herein are implemented by suitably configured
computers and/or
suitably configured processors. Throughout the disclosure where a processor,
computer or
computer readable medium is referenced such a reference may include one or
more
processors, computers or computer readable media in communication with each
other through
one or more networks or communication mediums. The one or more processors
and/or
computers may comprise any suitable processing device, such as, for example,
application
specific circuits, programmable logic controllers, field programmable gate
arrays,
microcontrollers, microprocessors, computers, virtual machines and/or
electronic circuits.
The one or more computer readable media may comprise any suitable memory
devices, such
as, for example, random access memory, flash memory, read only memory, hard
disc drives,
optical drives and optical drive media, or flash drives. Further, where a
communication to a
device or a direction of a device is referenced it may be communicated over
any suitable
electronic communication medium and in any suitable format, such as, for
example, wired or
wireless mediums, compressed or uncompressed formats, encrypted or unencrypted
formats.
[0068] One or more processors and/or computers in communication with each
other through
one or more networks or communication mediums may be collectively or
individually
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referred to herein as a "computer system". Actions performed by a computer
system may be
understood to be performed by one or more processors, and/or may be understood
to be
performed by other components of one or more computers in the computer system
(e.g. at an
input device such as a keyboard, touch screen, computer mouse, etc.; at an
output device such
as a display, an audio speaker, a haptic feedback motor, etc.; and/or at other
components).
[0069] Aspects of the present disclosure provide systems and methods for
mapping and
evaluating visual distortions caused by metamorphopsia. The methods involve
showing a
subject initial patterns which may be adjusted to appear non-distorted to the
subject. A
reference pattern within the subject's region of distorted vision is generated
from the initial
patterns and is used to promote suitable head position and eye fixation
throughout the
subsequent steps of the methods. Further patterns within the distorted region
are shown to the
subject and are adjusted to appear non-distorted to the subject. Patterns may
be non-
adjustable outside of the distorted region. The adjusted patterns may be used
to define a
distortion map which allows images to be distorted in a complementary way so
that the
images appear non-distorted to the subject. The distortion map may undergo
interpolation to
add detail to the information provided by the adjusted patterns.
[0070] Systems according to particular embodiments may comprise a processor
configured to
perform such methods using a display. Non-transitory computer-readable media
may be
provided with instructions, which (when executed by a suitably configured
processor), cause
the processor to perform such methods.
[0071] In order to fully appreciate certain aspects of the present disclosure,
particular features
of the typical human eye should be brought to mind. Figure 2A is a schematic
cross-sectional
illustration of an example eye 200. The depicted portion of eye 200 is
substantially covered
by an example retina 202 (and thus substantially opposes the portion of the
eye housing the
iris, lens, cornea, etc.). Retina 202 comprises several regions, including the
macula 204, the
fovea 206, and the foveola 208. Retina 202 is partially obstructed by the
optic disc 212,
which overlays the optic nerve (not shown).
[0072] Retina 202 is an arrangement of photoreceptors, which are divided into
cones
(smaller, densely-packed photoreceptors which provide higher resolution vision
as well as
colour sensitivity) and rods (larger photoreceptors which provide low light
vision and other
functions). These photoreceptors are not distributed uniformly or in regular
geometric array.
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In general, cones tend to be more concentrated towards the center of retina
202 (particularly
within macula 204), and rods are primarily found further from the center of
retina 202. For
instance, Figure 2C is a photograph of a macular region 260 (i.e. located
within macula 204
of example retina 202) which primarily comprises cones 262. Figure 2D is a
photograph of a
peripheral region 270 (i.e. located outside of macula 204) which comprises a
much greater
proportion of rods 272.
100731 Due to the greater proportion of cones 262 in macula 204, visual acuity
tends to be
much greater within macula 204 than outside macula 204. Macula 204 typically
has a
diameter of approximately 6 mm (i.e. an angular diameter of approximately 18
). Cones 262
are even more densely packed within fovea 206, which typically has a diameter
of
approximately 1.5 mm (i.e. an angular diameter of approximately 5 ). Foveola
208 typically
comprises only cone photoreceptors, and provides the greatest visual acuity of
any region of
retina 202 in a typical eye. Foveola 208 typically has a diameter of
approximately 0.35 mm
(i.e. an angular diameter of approximately 1.2 ) Nerve endings are also more
densely
concentrated in fovea 206 and foveola 208, resulting in much more visual
information being
transmitted from these areas.
[0074] The relative visual acuity of each region of example retina 202 is
depicted in chart
230 of Figure 2B. Axis 242 represents visual acuity, and ranges from 0
(corresponding to no
vision) to 1 (corresponding to peak visual acuity, found in the center of
foveola 208). Axis
244 represents the angular position of each point in the retina relative to
the center of foveola
208. Line 232 depicts the visual acuity of various portions of the retina. For
example, point
238 corresponds to the visual acuity of foveola 208 at its center. The portion
of line 232
within range 236 corresponds to the visual acuity of fovea 206. The portion of
line 232 within
range 234 corresponds to the visual acuity of macula 204. Region 240
corresponds to the
blind spot coinciding with optical disk 212.
[0075] As shown in Figure 2B, visual acuity drops off sharply outside of
foveola 208.
Threshold 246 corresponds to maximal visual acuity (e.g. 20/20 vision), which
is only
achieved in the depicted example at point 238. Threshold 248 corresponds to
50% of the
visual acuity at threshold 246, (e.g. 20/40 vision), and is only achieved in
the depicted
example within approximately 0.75 mm (i.e. within an angular distance of
approximately
2.5 ) of the center of foveola 208.
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[0076] Figure 3A shows an example image 300A received on an example normal
retina. The
image comprises, in this example, a straight line 302. Gridlines 304 represent
the
arrangement of a normal retina without displacement (i.e. without
metamorphopsia). Axes
306 and 308 are provided for reference, and correspond to nominal positions on
the retina.
Line 302 lies substantially straight on the retina (curvature of line 302 due
to the shape of
curvature of the eye is omitted for the sake of example), which is reflected
by the registration
of line 302 with gridlines 304. Figure 3B shows a corresponding perception
300B of image
300A by a subject with a normal retina. Perceived line 312 corresponds to line
302. Perceived
line 312 is perceived as straight, as indicated by the registration of line
312 with gridlines
314. Axes 316 and 318 substantially correspond to axes 306 and 308,
respectively, although
axes 316 and 318 correspond to positions in perceived space (rather than
positions on the
retina). As would be expected, Figures 3A and 3B illustrate an accurate
perception of a
straight line by a normal eye.
[0077] It will be appreciated that, in the above and following examples,
straight lines (such as
line 302) are used for the simplicity of illustration. Other patterns,
including geometric shapes
(e.g. squares, rectangles, circles, ellipses, parallelograms, triangles,
etc.), irregular shapes
(e.g. inkblots, outlines of arbitrary shapes, etc.), photographs, and/or any
other suitable visual
indicia may be used.
[0078] Figure 4A shows an example image 400A received on an example retina
with
metamorphopsia. Gridlines 404 are distorted to reflect the displacement of
portions of the
retina. The same straight line 302 is projected onto the metamorphopsia-
affected retina in the
same location as in Figure 3A, although (due to the displacement of a portion
of the retina) it
is sensed by different photoreceptors. Figure 48 shows a corresponding
perception 400B of
image 400A by a subject with the example metamorphopsia-affected retina of
Figure 4A.
Due to the displacement of a portion of the retina, perceived line 412 is
perceived as being
non-straight within the perceived space indicated by gridlines 414. This
distortion is due to
the physiological displacement of a portion of the retina as well as
subsequent cognitive
processing which interprets the stimuli received by the retina and transmitted
to the brain.
[0079] The present disclosure provide systems and methods for mapping the
distortions
perceived by a subject, thereby generating a distortion map which maps points
in an image
(such as image 400A) to points in a perceived space (such as in perception
400B). A
distortion map, once generated, may be used to "correct" images shown to the
subject so that
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the images are perceived by the subject without distortion. This may be done
by distorting
images in a manner complementary to the distortions represented by the
distortion map. Such
corrective distortions (e.g. as represented by a perception map complementary
to the
distortion map) may be used for diagnostic purposes, to produce corrective
optical and/or
electronic devices, and/or for other purposes.
[0080] A variety of issues can arise when generating a distortion map and/or
when correcting
images. In particular, Figures 5A, 5B, and 5C show examples of some potential
issues.
[0081] For example, if the subject's eye is permitted to move during testing,
the position of
the image on the retina may shift. Such movement is relatively common, since
involuntary
ocular tremors, ocular drift, and micro saccades may cause the eye to move
during the course
of testing. In such circumstances, the distortion map may reflect a
translational distortion in
one eye which is not truly present (or is present to a lesser or greater
extent). The same
translational distortion may not be determined during testing of the other
eye, which may lead
to double vision, as shown in perception 500A of Figure 5A. Rather than
perceiving a single
straight line 502 corresponding to line 302, the subject may experience double
vision, e.g. by
perceiving a displaced line 504 in one eye which is out of registration with
line 502 in the
other eye. Accordingly, in addition to addressing localized distortions (e.g.
in addition to
straightening a distorted line), it is desirable to ensure that the subject's
eye remains fixed on
a particular point in the image (e.g. image 400A) during generation of the
distortion map so
that the corrected image will be properly aligned in both eyes.
[0082] Figure 5B depicts an alternative example perception 500B resulting from
a subject's
example eye movement. In this case, rather than introducing a translational
error, the
distortion map may incorrectly reflect a perceived distortion in a portion of
the image (e.g.
image 400A). For example, a subject may be presented with image 400A (which,
as depicted,
is perceived as distorted in the range from -2 to 2 along axis 306), and the
subject may over-
or under-report distortion in a particular location (e.g. in the vicinity of
row 0 on axis 306)
due to microsaccades, a shift in the subject's fixation point, and/or due to
other eye
movement resulting in image 400A falling on a different area of the subject's
retina. Such
eye-movement-induced error may result in an under- or over-correction of the
corrected
image, resulting in distorted perceptions such as perception 500B.
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10083] Figure 5C depicts an example perception 500C resulting from a subject
adjusting
portions of a distortion map corresponding to portions of a retina which are
not displaced (i.e.
portions where there is no true distortion). For example, a subject may adjust
distorted
portions of an image along the periphery of the image and subsequently adjust
remaining
portions of the image so as to ensure that the lines remain straight. It is
generally more
difficult to determine whether lines are parallel, horizontal, vertical or
otherwise spatially
oriented than it is to determine whether they are straight. This can give rise
to a straight
perceived line 508 which is out of registration with the perceived space
indicated by gridlines
414.
100841 Figure 6A depicts an example image 600A comprising a corrected line
604. Gridlines
404 correspond to the same metamorphopsia-affected retina as shown in Figure
4A. In this
example, corrected line 604 is perceived as straight line 612, as shown in
perception 600B of
Figure 6B. Notably, in this example, corrected line 604 is not merely the
geometric inverse of
perceived line 412 of Figure 4B. This helps to demonstrate that the
relationship between how
a subject may perceive a particular "normal" pattern and its corresponding
corrected pattern
may be more complex, in some circumstances, than merely finding the inverse of
the
distorted perception of the pattern. Accordingly, it may be advantageous in
some
circumstances to generate a perception map from the distortion map, and to
generate
approximations of images as perceived by the subject based on the perception
map.
100851 Figure 7 depicts an example method 700 for generating a perception map.
Method
700 may be considered to comprise several sub-methods, namely a calibration
method 710, a
reference pattern generation method 730, a distortion mapping method 750, and
a perception
map generation method 770.
100861 Calibration method 710 comprises block 712 which involves calibrating a
system for
mapping distortions to present images so that they are received at the
subject's retina in a
consistent way between mappings. Such a system may, for example, comprise
system 800, as
shown in Figures 8A and 8B. For the purpose of the following disclosure,
reference will
generally be made to system 800 and its components with the understanding that
the methods
described herein may be performed by other suitably-configured systems. System
800
comprises an ophthalmic forehead and chin rest, and particularly comprises a
support 804 for
receiving the head of a subject 802 (subject 802 is not a component of system
800, but is
shown for the purpose of better illustrating the functionality of support
804). Support 804
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may comprise a chin rest 808 and/or a head rest 806. The head and chin of
subject 802 may
be secured to chin rest 808 and/or head rest 806 in order to limit head
movement (particularly
movement towards and/or away from a display 810).
[00871 Display 810 is provided facing support 804. Display 810 may be in
communication
with a computer system 811 (for the purposes of this disclosure, "in
communication with"
includes being integrated with display 810), which may control display 810 to
display
graphical indicia such as pattern 814 to subject 802. In some embodiments,
display 810 has
sufficient resolution to display graphical indicia without significant
pixelation, aliasing,
and/or other visual artifacts. Display 810 is preferably sufficiently large
and positioned
sufficiently near to support 804 to accommodate a field of view 820 which
includes the
subject's distorted areas of vision. In some embodiments, display 810
accommodates a field
of view of at least 25 (i.e. having angles 818 and/or 828 of at least 25 )
along at least one
axis (e.g. along horizontal axis 308). In some embodiments, the center of
display 810 is
directly in front of the eye 803 of user 802; that is, the surface of display
810 may be
perpendicular to the line of sight of user 802.
[0088] Further, display 810 is preferably calibrated to provide an accurate
image; that is,
display 810 is preferably calibrated to display images centered in the screen
and
geometrically true (i.e. without stretching, compressing, or cropping the
image). Display 810
may display images with uniform linear scaling. In some embodiments, display
810 displays
images which are adjusted so as to be geometrically true when received at the
retina, even
though such adjustment may result in the images being deformed at the surface
of display
810. For example, a flat display 810 positioned close to a subject may result
in an image
which is displayed geometrically truly at the surface of display 810 to not be
geometrically
true at the subject's retina, since the center of display 810 may be closer to
the subject's
retina than the edges of the display. System 800 may be provided with the
distance from the
subject's eye to display 800 (e.g. as measured relative to the center of
display 810) as well as
the size of the display and/or the physical or angular size of the image to be
displayed. On the
basis of this or other information, system 800 may cause adjusted images 810
to be displayed
to the subject which account for angular distortions caused by varying
distances between the
surface of display 810 and the subject's retina. In some embodiments, if
display 810 is known
to introduce one or more inaccuracies to displayed images, system 800 may be
calibrated to
take into account (e.g. counteract) such inaccuracies.
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[0089] System 800 may be configured to present images to subject 802 with
consistent
angular sizes. However, displays 810 generally display images based on a
linear size (e.g.
expressed in pixels, inches, or the like). Therefore, in order to provide
consistently-sized
images to the retina of subject 802, the physical dimensions of at least a
part of system 800
must be known. In some embodiments, distance m indicated by line 812 between
eye 803 (or
support 804) and display 810 may be predetermined, measured, and/or otherwise
determined.
For example, distance m may be measured manually and input into computer
system 811,
and/or computer system 811 may control the position of display 810 and/or
support 814 to
enforce a particular distance m. In some embodiments, where a range of
acceptable distances
m are available, display 810 is positioned at the maximum acceptable distance
from support
804 (e.g. the largest distance available which provides at least a 25 field
of view at display
810).
[0090] Once the distance m has been determined, the linear size L of an image
displayed on
display 810 may be determined according to the following equation:
A
L = 2m tan.
where A is the angular size of the image to be displayed on display 810.
Although angular
measurements are generally presented herein in degrees, they may alternatively
or
additionally be presented in radians. For example, the above equation is
expressed in radians.
[0091] Correspondingly, the angular size A of an image having a known linear
size L (such
as a test image displayed during calibration) may be determined according to
the following
equation:
A = 2 tan-1-2m
where A, L and m have the meaning discussed above.
[0092] In some embodiments, system 811 may display images based on retinal
image sizes -
that is, the size of an image as received on the retina of subject 802. Based
on the angular size
A, system 811 may determine the retinal size R of an image according to the
following
equation:
CA 02880856 2015-02-03
R = L ¨
m
where L and m have the meaning discussed above and d is the distance from the
lens to the
retina of eye 803 of subject 802. The retinal image size R provides a common
basis of
measure that may be used across different implementations and different
subjects. Retinal
image sizes may, in some circumstances, be used in conjunction with distances
of retinal
disturbances as measured using optical coherence tomography and/or other
techniques.
[0093] The dimensions I of display 810 and/or a portion of display 810 may be
used to drive
display 810 to display the image at the appropriate linear size (e.g. if L is
intended to be 10
centimeters wide and the width of display 810 is 20 centimeters, then display
810 may be
driven to display the image across 50% of the width of display 810). The
dimensions I may
be predetermined, measured, and/or otherwise determined. For example, a
pattern 814 may
be displayed on display 810 and measured. For instance, pattern 814 may
comprise a straight
line stretching diagonally across display 810 (assuming a rectangular display
810) between
two predetermined display coordinates. In some embodiments, pattern 814 may be
selected to
be as large as possible so as to reduce the proportionate magnitude of error
in measurement.
For instance, pattern 814 may comprise a line stretching from one corner of
display 810 to a
diagonally-opposing corner. Alternatively, or in addition, dimensions of
display 810 and/or a
portion thereof, such as vertical dimension 816 (I,) horizontal dimension 826
(/h), and/or a
diagonal dimension (not shown) may be predetermined or otherwise determined.
[0094] Computer system 811 may determine the maximum linear size required to
display
images in the subsequent tests. If that linear size exceeds the dimensions of
display 810, then
computer system 810 may reduce the viewing distance m between display 810 and
subject
802, display a scaled-down version of one, some, or all images during the
test, select a
different display 810 of a suitable (larger) size, and/or take other action.
Alternatively, or in
addition, computer system 811 may present provide direction to an operator to
perform one
or more of those options. Alternatively, or in addition, computer system 811
may prompt an
operator to choose between two or more such options.
[0095] At various times this disclosure will refer to subject 802 and/or an
operator of system
800 interacting with system 800. It will be understood that subject 802 and/or
an operator of
system 800 may interact with computer system 811 via input device 813 and/or
via any other
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suitable device (e.g. a computer terminal in communication with system 800, a
mobile
device, a computer mouse, a joystick, a rotary knob, and/or any other input
device known in
the art or later discovered). In some embodiments, subject 802 may also be an
operator of
system 800.
[0096] Returning to Figure 7, once the system (e.g. system 800, as described
above) has been
calibrated, method 700 may proceed to block 714 which involves determining a
distortion
region. By determining the region of the field of view 820 of subject 802
which is distorted,
method 700 and/or system 800 may prevent subject 802 from adjusting portions
of test
patterns which lie outside of the distortion region (and thereby avoid
introducing certain
errors to the distortion map). Figures 9A, 9B, 9C, 9D, 9E, 9F, 9G, 9H, 91, 9J,
9K and 9L
illustrate example methods of identifying a distortion region.
[0097] Figure 9A shows an example calibration display 902A (which may be
displayed to
subject 802 by display 810). Display 902A comprises a fixation target 906 for
subject 802 to
fixate eye 803 on. Fixation target 906 may comprise a dot, a crosshair
(sometimes referred to
by the inventor(s) as an "X"), and/or any other suitable shape. Fixation
target 906 may have a
visual angular size (e.g. an angular diameter) of approximately 0.5 . Fixation
targets 906
which are no larger than approximately 0.5 have been found to promote
fixation stability in
some circumstances.
[0098] In example display 902A, no boundary lines are shown. In some
embodiments,
display 902A is not shown to subject 802 (e.g. block 714 may begin with
display 902B,
discussed below). In some embodiments, display 902A comprises a test pattern
(such as an
Amsler grid, a multi-resolution grid as shown in Figure 10A, and/or some other
pattern) to
assist subject 802 in identifying general areas in field of view 820 where
distortions are
present. Subsequently, display 902B may be displayed to subject 802.
[0099] Figure 9B shows an example perception of calibration display 902B.
Display 902B
comprises a boundary line 910. In the depicted example, the perception of
boundary line 910
is distorted near to fixation target 906. Boundary line 910 is actually
straight, so it can be
determined that boundary line 910 passes through a distortion region which
happens to be
near fixation target 906. Subject 802 may move boundary line 910 until it lies
just outside of
the distortion region (i.e. until it appears straight). Subject 802 may be
constrained in the
movement of boundary lines such as boundary line 910 so that boundary lines
may only be
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CA 02880856 2015-02-03
moved orthogonally to the direction of the line. For example, since boundary
line 910 runs
horizontally, subject 802 may only be permitted to move boundary line 910
vertically.
Subsequently, display 902C may be displayed to subject 802.
[0100] Figure 9C shows an example calibration display 902C. Boundary lines 912
and 914
have been set by subject 802 to lie just outside of the distortion region;
boundary lines 912
and 914 lie on opposing sides of that region. For example, boundary line 912
may correspond
to boundary line 910 after boundary line 910 has been moved vertically upwards
to lie
outside of the distortion region. After confirming the location of boundary
line 912, subject
802 may similarly set the location of a parallel boundary line 914.
Subsequently, display
902D may be displayed to subject 802.
[0101] Figure 9D shows an example perception of a calibration display 902D.
Dashed lines
908 correspond to previously-set boundary lines (in this case, boundary lines
912, 914).
Dashed lines 908 may be displayed to subject 802 (and may or may not be
dashed) or may be
hidden from view. A new boundary line 920 is provided. As with boundary line
910, subject
802 may move boundary line 920 until it lies just outside of the distortion
region. Boundary
line 920 may run in any direction. In some embodiments, and in the depicted
example,
boundary line 920 runs in a direction orthogonal to previously-set boundary
lines 912, 914.
Subsequently, display 902E may be displayed to subject 802.
[0102] Figure 9E shows an example calibration display 902E. As with boundary
lines 910
and 914, boundary lines 922 and 924 have been set by subject 802 to lie just
outside of the
distortion region and on opposing sides thereof. Subsequently, display 902F
may optionally
be displayed to subject 802. Alternatively, the distortion region may be
defined based on the
area enclosed by lines 908, 922, 924 (see Figure 9K for an example of this,
discussed below).
[0103] Figure 9F shows an example perception of a calibration display 902F. A
new
boundary line 930 is provided. As with boundary lines 910 and 920, subject 802
may move
boundary line 930 until it lies just outside of the distortion region.
Boundary line 930 may run
in any direction. In some embodiments, and in the depicted example, boundary
line 930 runs
in a direction diagonal to one or more of the previously-set lines 908.
Subsequently, display
902G may be displayed to subject 802, as shown in Figure 9G. Boundary lines
932 and 934
have been set by subject 802 substantially as described above. Subsequently,
display 902H
may be displayed to subject 802.
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[0104] Figure 9H shows an example perception of a calibration display 902H. A
new
boundary line 940 is provided. Subject 802 may move boundary line 940
substantially as
described above. In some embodiments, and in the depicted example, boundary
line 940 runs
in a direction diagonal to one or more of the previously-set lines 908 and
orthogonal to
boundary line 930. Subsequently, display 9021 may be displayed to subject 802,
as shown in
Figure 91. Boundary lines 942 and 944 have been set by subject 802
substantially as
described above. Subsequently, display 902J may be displayed to subject 802.
[0105] Figure 9J shows an example calibration display 902J. Distortion region
950 is defined
between lines 908. In the depicted example, distortion region 950 is
determined to be the
intersection of the areas between previously-defined pairs of parallel
boundary lines 912 and
914, 922 and 924, 932 and 934, and 942 and 944.
[0106] Figure 9K shows an example calibration display 902K. An alternative
example
distortion region 960 is defined between lines 908 (which correspond to the
boundary lines
908, 922, and 924 of Figure 9E). In the depicted example, distortion region
960 is determined
to be an ellipse defined between lines 908. In an alternative embodiment, a
distortion region
may be determined to be the intersection of the areas between previously-
defined pairs of
parallel boundary lines 912 and 914 as well as 922 and 924 (which, in this
example, would
result in a rectangular distortion region), substantially as described above
with reference to
Figure 9J.
[0107] Figure 9L shows an example calibration display 902L. An alternative
example
distortion region 970 is shown. In the depicted example, it is not necessary
for boundary lines
908 to have been defined. Distortion region 970 may be defined by a subject
802 selecting a
location, size, and/or shape for distortion region 970 (e.g. via input device
813).
[0108] It is not necessary that distortion regions 950, 960, 970 exactly
correspond to the
distortion perceived by subject 802. Indeed, in most circumstances, distortion
regions 950,
960, 970 will be slightly larger than the distortion perceived by subject 802.
However, it is
generally advantageous for distortion region 950, 960, 970 to fully enclose
the distortion
perceived by subject 802, and to include relatively little of the surrounding
non-distorted
area.
[0109] If subject 802 perceives multiple distortion regions, the above-
described process of
block 714 may be repeated until all distortion regions of interest have been
identified. For the
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CA 02880856 2015-02-03
sake of simplicity, the union of all such identified distortion regions will
be referred to simply
as "the distortion region" in the following disclosure.
101101 Returning to Figure 7, method 700 (and, more particularly, calibration
method 710)
may continue to block 716 which involves selecting a representation for
patterns to be
displayed to subject 802. As is discussed in greater detail below, patterns
may be presented to
subject 802 during method 700 at various times (including, in some
embodiments, during the
process of block 716). In some embodiments, these patterns comprise arrays of
indicia (such
as circles, squares, other geometric shapes, irregular shapes, images, and/or
other indicia)
which may be connected by a line. One such pattern is shown in Figure 10B,
which provides
variously-sized indicia 1014, 1024, and 1034 (in this example, represented as
dots) connected
by variously-sized lines 1016, 1026, and 1036. Although in some circumstances
providing
lines is advantageous, in some embodiments indicia are provided without lines,
or with other
connecting features. In some embodiments, indicia have an angular size in the
range of 0.10
to 0.5 , with larger sizes within that range generally being selected for
patients with less
visual acuity. In some embodiments, connecting lines have a thickness in the
range of 0.05
and 0.10. In some embodiments, connecting lines have a thickness in the range
of 5% to 15%
the angular size of their corresponding indicia. In some embodiments,
connecting lines have a
thickness that is not based on the angular size of their corresponding
indicia.
[0111] The extent and severity of metamorphopsia may vary from subject to
subject, as can
relative visual acuity. Indicia of different sizes, shapes, and colors may
appear to a particular
subject to be more or less distorted than other indicia. Different size ratios
between indicia
and their corresponding lines may also, or alternatively, impact a subject's
perception of
distortion. Accordingly, subject 802 may be presented with several patterns,
simultaneously
and/or sequentially. Subject 802 may be prompted to select a pattern from the
patterns
presented. Computer system 811 may store the selection and subsequently
present patterns
according to the subject's selection. The patterns may be presented at least
partially within
the distortion region to assist subject 802 to determine the extent of
distortion without having
to shift the fixation of eye 803.
[0112] In some embodiments, subject 802 may be able to vary aspects of
patterns directly;
for example, subject 802 may select a line thickness and/or an indicia size
(and/or shape,
color, and/or other aspects of a pattern) via input device 813. In some
embodiments, patterns
are predetermined and/or dynamically generated and presented to subject 802
for selection. In
CA 02880856 2015-02-03
some embodiments, subject 802 may provide a selection to an operator of
computer system
811 and the operator may input the selection into computer system 811.
[0113] As noted above, various patterns are presented to subject 802 during
method 700,
including during calibration method 710, reference pattern generation method
730, and/or
distortion mapping method 750. Patterns may be displayed differently depending
on the part
of the retina by which they are likely to be perceived. For example, indicia
may be presented
in smaller sizes in higher-resolution areas of the visual field (the varying
acuity of the retina
is discussed above, with reference to Figures 2A, 2B and 2C). It is generally
preferable for
the granularity (i.e. resolution) of the pattern in a given location to
generally correspond to
the acuity of the corresponding portion of the retina (i.e. the portion of the
retina on which the
image of the pattern falls). The pattern may be presented as a grid divided
into a plurality of
portions with different resolutions generally corresponding to the acuity of
the corresponding
portions of the retina. Any number of different portions (and therefore
different resolutions)
may be provided. In some embodiments, three portions are provided, as
discussed further
below in reference to Figure 10A.
[0114] Figure 10A shows an example multi-resolution grid 1000A. Multi-
resolution grid
1000A comprises a low-resolution portion 1010 (indicated by sparse grid lines
1012) on the
periphery, a medium-resolution portion 1020 (indicated by relatively more
dense grid lines
1022), and a high-resolution portion 1030 (indicated by significantly more
dense grid lines
1032). In the depicted example, portions 1010, 1020, 1030 are concentric and
centered on
fixation target 1004. Each portion 1010, 1020, 1030 may comprise a plurality
of points (e.g.
located at the intersections of grid lines 1012, 1022, and 1032). As will be
discussed in
greater detail below, subject 802 may adjust patterns based on these points.
[0115] Grid lines 1012, 1022, and 1032 are provided to better understand multi-
resolution
grid 1000A, and are not necessarily displayed to subject 802. Each
intersection of grid lines
1012, 1022, and 1032 may correspond to a point in a distortion map. Thus, the
distortion map
is of higher resolution near to the center of vision of subject 802 (which has
greater visual
acuity, as illustrated in Figure 2B), and lower resolution towards the
periphery (which has
lesser visual acuity, as illustrated in Figure 2B). In some embodiments,
portions 1010, 1020,
and/or 1030 are sized to correspond to be angular sizes of macula 204, the
fovea 206, and
foveola 208, respectively. For example, portion 1030 may have an angular
diameter (or, more
particularly in the case of the depicted square portion 1030, an angular side-
length) of
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approximately 1 , portion 1020 may have an angular diameter of approximately 6
, and
portion 1010 may have an angular diameter in excess of 20 .
[0116] In some embodiments, portions 1010, 1020, and/or 1030 may be
differently sized
and/or differently shaped. For example, portions 1020 and/or 1030 may be
circular, elliptical,
or otherwise shaped. In general, the preferred size of a particular portion
will depend on the
acuity of the corresponding part of the retina and on the size of the portion.
A portion of the
pattern which is much higher-resolution than its corresponding portion of the
retina may
impose a burden on the subject (since the excess resolution is "wasted" and
requires
additional and unnecessary attention from the subject), whereas a portion of
the patter which
is much lower-resolution than its corresponding portion of the retina may
result in small
distortions (e.g. located entirely between grid lines 1012) remaining
undetected and thus
uncorrected.
[0117] Figure 10B shows an example multi-resolution grid 1000B with
substantially the
same features as multi-resolution grid 1000A and patterns overlaid thereon. In
particular, a
low-resolution pattern 1018 (comprising large indicia 1014 and corresponding
line 1016) is
overlaid on low-resolution portion 1010, a medium-resolution pattern 1028
(comprising
medium indicia 1024 and corresponding line 1026) is at least partially
overlaid on medium-
resolution portion 1020, and a high-resolution pattern 1038 (comprising small
indicia 1034
and corresponding line 1036) is at least partially overlaid on high-resolution
portion 1030.
[0118] As depicted, each portion 1010, 1020, 1030 has an associated
representation for
indicia and/or lines therein. In some embodiments, including the depicted
embodiment,
patterns passing through high-resolution portion 1030 may be represented
according to the
representation associated with high-resolution portion 1030 even outside of
high-resolution
portion 1030. Patterns passing through medium-resolution portion 1020 and not
high-
resolution portion 1030 may be represented according to the representation
associated with
medium-resolution portion 1020. In some alternative embodiments, a particular
pattern may
be represented according to multiple representations; for example, a pattern
may comprise
small indicia 1036 within high-resolution portion 1030 and medium indicia 1026
within
medium resolution portion 1020.
[0119] In some embodiments, including the depicted embodiment, patterns 1018,
1028, 1038
comprise lines 1016, 1026, 1036, respectively. Lines 1016, 1026, 1036 may
assist subject 802
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in assessing the straightness of the associated array of indicia 1014, 1044,
1034. In some
embodiments, lines 1016, 1026, 1036 are thin relative to their associated
indicia 1014, 1024,
1034. For example, each line 1016, 1026, 1036 may comprise a thickness not
exceeding 20%
of a diameter of the associated indicia 1014, 1024, 1034. Lines 1016, 1026,
1036 may
visually connect their associated indicia 1014, 1024, 1034, e.g. by running
through the
centers of their associated indicia 1014, 1024, 1034. In some embodiments,
lines 1016, 1026,
1036 are a different color than their associated indicia 1014, 1024, 1034.
101201 Returning to Figure 7, block 718 involves selecting a type of temporal
variation for
the selected patterns. Peripheral indicia (i.e. indicia perceived in the
periphery of subject
802's retina) may appear to fade over time due to a phenomenon known as the
Troxler effect.
It is desirable to prevent or delay the fading of peripheral indicia in order
to enable subject
802 to use peripheral indicia as reference points. Causing peripheral indicia
to move or
otherwise vary in appearance over time may prevent or delay the fading of
peripheral indicia.
The particular style of variation most suitable to ameliorating the Troxler
effect without being
unduly distracting may vary from subject to subject. Accordingly, subject 802
may be
presented with several styles of variation, simultaneously and/or
sequentially. Subject 802
may be prompted to select a style of variation from those presented. Computer
system 811
may store the selection and subsequently present patterns with the selected
style of variation.
[0121] In some embodiments, only indicia which are at least 70 removed from
the fixation
target (i.e. indicia positioned at at least 7 retinal eccentricity) are made
to vary in appearance
in the selected manner. In some embodiments, indicia must also, or
alternatively, be outside
of the displacement region in order to vary in appearance in the selected
manner. For
example, in some embodiments, only indicia which are at least 7 removed from
the fixation
target and which are also at least 7 removed from the boundary of the
displacement region
may be made to vary in appearance in the selected manner.
101221 A variety of variations are possible. A particular variation type which
the inventors
have found to give good results in some circumstances is movement of indicia
(such as
indicia 1014 in Figure 10B) in the direction of their associated line (e.g.
along line 1016 in
Figure 10B) once roughly every 5 seconds, alternating between movement in one
direction
(e.g. left) and the opposing direction (e.g. right). The indicia may move by,
for example, half
the distance between indicia. Movement may be substantially instantaneous
(i.e. indicia may
be stationary for 5 seconds, change location between frames and/or between
refresh cycles of
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display 810, and remain stationary for another 5 second before changing
location again).
Alternatively, or in addition, movement may be animated over a period of time.
[0123] Other types of variation are possible. For example, indicia may shift,
bounce, stretch,
rotate, pulse, grow, shrink, change color, and/or otherwise change their
location or
appearance. Indicia may move along a path other than (or in addition to) their
associated
lines, or may move in place (e.g. via rotation).
[0124] Calibration method 710 may comprise some or all of the above-identified
blocks 712,
714, 716, 718. In some embodiments, certain steps may be omitted or performed
in a
different order. For example, the block 718 selection of a pattern variation
may not be
performed, or may be performed before or in parallel with the block 716
selection of a pattern
representation. Similarly, the block 716 selection of a pattern presentation
may not be
performed in some embodiments (e.g. the pattern representation may be
predetermined) or
may be performed before or in parallel with one or more of block 712 and 714.
[0125] Once calibration method 710 is complete, method 700 may continue to
reference
pattern generation method 730. Block 732 involves generating an initial
reference pattern.
The initial reference pattern passes through the distortion region and is
adjusted by subject
802 so that the perception by subject 802 of the reference pattern is non-
distorted. The initial
reference pattern will appear distorted to an observer with a normal retina.
The process of
block 732 is illustrated in Figures 11A, 11B, 11C, 11D, 11D, and 11F
(collectively and
individually, Figure 11).
[0126] Figure 11A shows an example adjustment display 1102A having a fixation
target
1104 and a distortion region 1106 (distortion region 1106 may be, but is not
necessarily,
displayed to subject 802). A pattern 1110 passes through distortion region
1106; pattern 1110
comprises indicia and a line substantially as described above.
[0127] Pattern 1110 passes through a point 1108. Indicia is displayed at point
1108. In some
embodiments, including in the depicted embodiment, point 1108 is the point
within distortion
region 1106 which is nearest to (is among the points nearest to) fixation
target 1104. Pattern
1110 passes through point 1108 in a particular direction (e.g. horizontally).
Note that point
1108 may be, but is not necessarily, on the boundary of distortion region
1106. In
circumstances where fixation target 1104 is located inside distortion region
1106, point 1108
may be located at fixation target 1104. In such circumstances, fixation target
1104 may be
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represented by indicia which differ from the indicia of pattern 1110; for
example, where
pattern 1110 comprises several dots, fixation target 1104 may be represented
by a crosshair
(and/or an "X").
[0128] Portions of pattern 1110 lying within distortion region 1106 may appear
distorted to
subject 802. Subject 802 may select particular indicia of pattern 1110 and
move the indicia
until pattern 1110 appears non-distorted. In the case of a pattern 1110 which
comprises a
straight line, subject 802 may move the indicia of pattern 1110 until the
resulting pattern
appear straight. Subject 802 may move the indicia by providing inputs to input
device 813,
substantially as described above. In some embodiments, computer system 811
allows subject
802 to move indicia within distortion region 1106 but does not permit subject
802 to move
indicia outside of distortion region 1106. This restriction may, in some
circumstances,
prevent subject 802 from introducing certain errors into the distortion map as
illustrated, for
example, in Figures 5A, 5B, and 5C. Subject 802 may be further restricted to
moving indicia
in a direction orthogonal to pattern 1110 (e.g. vertically).
[0129] Figure 11B shows an example adjustment display 1102B having an adjusted
pattern
1120. Adjusted pattern 1120 corresponds to pattern 1110 after subject 802 has
moved indicia
so as to cause pattern 1120 to be perceived as straight while eye 803 of
subject 802 is fixed at
fixation target 1104. For example, the indicia formerly at point 1108 is now
located at
position 1118 (which may or may not be located at a point defined by the multi-
resolution
grid). As noted above, pattern 1110 (and, therefore, pattern 1120) may be
placed near to
fixation target 1104; in some circumstances, such a placement may cause
subject 802 to be
less likely to break fixation with fixation target 1104.
[0130] Figure 11C shows an example adjustment display 1102C having a pattern
1130
orthogonal to pattern 1110 (in this example, vertically). Pattern 1130 passes
through point
1118. In some embodiments, any adjustment to point 1108 (resulting in point
1118) may be
reflected in pattern 1130; for example, as depicted, point 1118 is slightly
displaced, as in
Figure 11B. As described above, subject 802 may adjust indicia in pattern 1130
within
distortion region 1106 to make pattern 1130 appear non-distorted (in this
example, straight),
thereby generating adjusted pattern 1140 shown in Figure 11D. Adjusted pattern
1140
comprises a point 1128 corresponding to point 1118 after adjustment by subject
802. Subject
802 may be restricted when making adjustments as described above with
reference to
adjusted pattern 1120.
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[0131] Once patterns 1120 and 1140 have been determined, an initial reference
pattern may
be generated. Figure 11E shows an example display 1102E having an example
initial
reference pattern 1150 based on adjusted patterns 1120 and 1140. Initial
reference pattern
1150 comprises a reference pattern segment 1150A which conforms to the shape
of adjusted
pattern 1120 (e.g. segment 1150A is coincident with the centers of each of the
indicia of
adjusted pattern 1120), and a reference pattern segment 1150B which conforms
to the shape
of adjusted pattern 1140 (e.g. segment 1150B may be coincident with the
centers of each of
the indicia of adjusted pattern 1140).
[0132] Although initial reference pattern 1150 may appear distorted to a
person with normal
vision, metamorphopsia-affected subject 802 may have perception 1102F as shown
in Figure
11F. That is, subject 802 may perceive initial reference pattern 1150 as a non-
distorted
perceived pattern 1160. In the depicted example, perceived pattern 1160
comprises segments
1160A and 1160B corresponding to segments 1150A and 1150B, respectively, each
of which
appears straight to subject 802 when eye 803 of subject 802 is fixed on
fixation target 1104,
provided that subject 802's head is similarly in registration with display
810.
[0133] In some embodiments, segments 1150A and 1150B comprise distorted lines
which
have different thicknesses than the lines of patterns 1120 and 1140. For
example, segments
1150A and 1150B may be approximately 50% thicker than segments 1150A and
1150B. A
thickness may be selected based on the subject's preference; for example, a
thickness which
the subject reports to be relatively less distracting may be selected. By
changing the thickness
of segments 1150A and 1150B relative to patterns 1120 and 1140, pattern 1150
is made
visually distinct from subsequently-displayed patterns (discussed further
below).
[0134] Although it is possible to provide as many indicia as there are
photoreceptors along a
given pattern 1120 or 1140, this is rarely practical (since subject 820 would
need to adjust
potentially tens of millions of indicia). Accordingly, it is generally
advantageous to provide a
smaller number of indicia in each pattern 1120 and 1140, e.g. in the range
from 40 to 60
indicia. A larger number of indicia may be provided when appropriate in the
circumstances,
such as where greater granularity is required for research purposes, where the
distortion
region is located around or near to the fovea, where the results of the
distortion mapping are
intended for use in the calibration of a corrective device with greater
granularity, or in other
circumstances. For example, the number of indicia may be selected by subject
802 and/or an
operator of system 800. The number of indicia may be determined according to
the resolution
26
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region on which the representation of patterns 1120 and 1140 are based ¨ for
example,
patterns displayed based on the representation associated with the low-
resolution region 1010
may have fewer indicia than those displayed based on the representation
associated with the
low-resolution regions 1020 and 1030 (as shown, for example, in Figure 10).
[0135] Accordingly, it is generally necessary to derive the locations of
portions of segments
1150A and 1150B which are located between the coordinates of the indicia of
patterns 1120
and 1140. This derivation may be performed by interpolation. Any suitable
interpolation
algorithm may be used for this derivation. In some embodiments, Bezier curves
and/or
splines are used to interpolate the locations of segments 1120 and 1140
between the
coordinates provided by the indicia of patterns 1120 and 1140 within
distortion region 1106.
[0136] Returning to Figure 7, once initial reference pattern 1150 has been
generated, it may
be tested at block 734. Such testing may comprise displaying pattern 1150 to
subject 802 and
confirming whether the pattern appears non-distorted (e.g. as shown in
perception 1102F of
Figure 11F) when subject 802 fixes eye 803 on fixation target 1104 and has
his/her head in
registration with display 810. Computer system 811 may provide a prompt for
such
confirmation to subject 802 via display 810, via another device, or via an
operator of system
811 (e.g. system 811 may prompt the operator to ask subject 811). Subject 802
and/or an
operator may provide an input to computer system 811 to indicate whether
perceived pattern
1160 appears non-distorted or not.
[0137] It may not be necessary, in some circumstances, for subject 802 to
perceive pattern
1150 as completely non-distorted. It may be sufficient for perceived pattern
1160 to
sufficiently approximate a non-distorted pattern. Accordingly, computer system
811 does not
require any particular level of perceived distortion (and, in any event, would
likely not be
capable of enforcing such a requirement using present technology), but rather
receives an
indication that the reference pattern either passes or fails to pass the test
of block 734.
[0138] If computer system 811 receives input which corresponds to a pass (e.g.
indicating a
substantially non-distorted pattern 1160), method 700 may proceed to block 752
of distortion
mapping method 750. Otherwise, if computer system 811 receives input which
corresponds
to a fail (e.g. indicating a distorted pattern 1160), method 700 may proceed
to block 736 of
reference pattern generation method 730.
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[0139] Block 736 involves displaying one or both of adjusted patterns 1120 and
1140 to
subject 802 and permitting subject 802 to further adjust patterns 1120 and
1140 substantially
as described above. Adjusted patterns 1120 and 1140 may be displayed
sequentially and/or
simultaneously. If adjusted patterns 1120 and 1140 are displayed
simultaneously, subject 802
may be permitted to adjust their point of commonality (i.e. point 1128) in any
permitted
direction, but adjustments to other points may continue to be restricted as
discussed above.
Method 700 (and thus method 730) returns to block 734 to repeat the testing of
the resulting
reference pattern, as described above.
[0140] As discussed above, there may be various points within distortion
region 1106 (e.g
corresponding to intersections of grid lines 1012, 1024, 1034 on multi-
resolution grid 1000A
of Figure 10A), some of which correspond to points on pre-adjustment patterns
1110 and
1130. Method 750 involves generating adjusted patterns for each point in the
distortion
region (e.g. distortion region 1106) so that each point is associated with
each required type of
adjusted pattern. For example, computer system 811 may require that each point
be
associated with a first linear pattern in a given direction and a second
linear pattern in an
orthogonal direction. For instance, in the depicted examples both horizontal
and vertical
patterns are used, so method 750 may involve generating horizontal and/or
vertical adjusted
patterns for each point in region 1106 which is not yet associated with
horizontal and/or
vertical adjusted patterns. Other types of adjusted patterns may
alternatively, or additionally,
be used; for example, method 750 may also, or alternatively, require that each
point be
associated with a diagonal linear pattern, with a non-linear (e.g. circular or
elliptical) pattern,
or with any other suitable type of pattern.
[0141] In the depicted example of Figure 11, point 1128 is the only point
which has
corresponding vertical and horizontal adjusted patterns. Other points along
adjusted pattern
1120 have only a corresponding horizontal adjusted pattern, so method 750 may
involve
generating vertical adjusted patterns for each of those points (and similarly
generating
horizontal adjusted patterns for each of the points other than point 1128
along adjusted
pattern 1140). Method 750 may involve generating both vertical and horizontal
adjusted
patterns for each remaining point in distortion region 1106 which is not
located along either
of adjusted patterns 1120 or 1140 (or their pre-adjustment counterparts,
patterns 1110 and
1130).
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[0142] Accordingly, block 752 involves determining whether additional patterns
remain to be
displayed to (and adjusted by) subject 802 in distortion region 1106. In some
embodiments,
including the depicted example, this determination comprises determining
whether any points
within distortion region 1106 do not yet have corresponding adjusted patterns
of a required
type (e.g horizontal or vertical). For example, Figure 12A shows an example
point 1204
which is already associated with horizontal adjusted pattern 1140, but is not
yet associated
with a vertical pattern (which, in this example, is required). Figure 12A is
discussed in greater
detail below.
[0143] Having identified a point which requires an additional adjusted
pattern, method 700
(and therefore method 750) may proceed to block 754. Block 754 involves
displaying further
patterns to subject 802, similar in some respects to the display of patterns
discussed above
(e.g. shown in Figure 11). An example of such a display 1202A is shown in
Figure 12A.
Display 1202A has a point 1204 and an additional pattern 1202 which includes
point 1204.
Note that point 1204 may be positioned according to previous adjustments which
have
included it, and not necessarily along gridlines 1012, 1022, or 1032. Subject
802 may adjust
indicia along pattern 1202 to generate adjusted pattern 1206, as shown in
display 1202B of
Figure 12B. This adjustment may be performed similarly to (and subject to the
same
constraints as) the adjustment of patterns 1110 and 1130, as discussed above.
[0144] In the example depicted, point 1204 only requires pattern 1202; in some
circumstances, a given point may require multiple additional patterns, each of
which may be
generated by block 754 substantially as described above (e.g. with reference
to block 732).
That is, block 754 may generate multiple patterns corresponding to the given
point
sequentially and/or in parallel. In some alternative embodiments, block 754
may generate
only one pattern for a given point, and may generate additional patterns for
the given point (if
necessary) on subsequent iterations.
[0145] In addition to pattern 1202, display 1202A (and/or display 1202B) may
also include
reference pattern 1140. Reference pattern 1150 may assist subject 802 in
ensuring that the
head of subject 802 remains in registration with display 810. As described
above, if subject
802 fixates eye 803 on fixation point 1104 and keeps his or her head in
registration with
display 810, reference pattern 1150 should appear substantially non-distorted.
Effectively,
reference pattern 1150 may provide a mechanism by which subject 802's visual
distortions
may be used to assist in avoiding common errors in the distortion mapping
process, since
29
CA 02880856 2015-02-03
movements of subject 802's head or eye 802 may result in reference pattern
1150 appearing
distorted.
[0146] Method 700 (and therefore method 750) may proceed to block 756, which
involves
testing adjusted pattern 1206 to determine whether adjusted pattern 1206
appears non-
distorted (or substantially non-distorted) to subject 802. Such testing may
comprise
displaying adjusted pattern 1206 to subject 802 and confirming whether the
pattern appears
non-distorted, as described above with reference to block 736 of method 730.
However, block
756 may also involve displaying reference pattern 1150 to subject 802 and
confirming that
both reference pattern 1150 and adjusted pattern 1206 appear non-distorted. If
adjusted
pattern 1206 appears non-distorted but reference pattern 1150 appears
distorted, it can be
concluded that subject 802's eye 803 or head is out of registration with
display 810 or
fixation target 1104 and that the block 756 test should be repeated (or simply
continued, since
an input to computer system 811 may not be necessary until a pass or fail has
been
determined).
[0147] If computer system 811 receives input which corresponds to a pass (e.g.
indicating a
substantially non-distorted pattern 1206 and reference pattern 1150), method
700 may
proceed to block 752 of distortion mapping method 750. Otherwise, if computer
system 811
receives input which corresponds to a fail (e.g. indicating a distorted
pattern 1206 while
reference pattern 1150 appears non-distorted), method 700 may proceed to block
758.
[0148] Block 758 involves displaying one or more of the adjusted patterns
generated by
block 754 (e.g. adjusted pattern 1206) to subject 802 and permitting subject
802 to further
adjust the pattern(s) substantially as described above with reference to block
736. As with
block 754, reference pattern 1150 may be displayed during the further
adjustment of the
pattern(s). Method 700 (and thus method 750) returns to block 756 to repeat
the testing of the
resulting adjusted patterns, as described above.
[0149] Once all of the points in distortion region 1106 have corresponding
adjusted patterns
of the required types, method 700 may proceed to perception map generation
method 770,
and in particular to block 772. Block 772 involves generating a distortion map
from the
adjusted patterns generated by methods 730 and/or 750 (such as reference
pattern 1150 and
adjusted pattern 1206). The union of the adjusted patterns may provide a grid
with distorted
lines which, when viewed by subject 810 while fixating eye 803 on fixation
target 1104 and
CA 02880856 2015-02-03
with the head of subject 802 in registration with display 810, appears
substantially non-
distorted. These grid lines provide a map from "normal" visual space to
"corrected" visual
space. For example, if point 1128 corresponds to point 1108 prior to subject
802's
adjustments, then the coordinates of point 1108 may be mapped to the
coordinates of point
1128.
[0150] For example, if point 1108 has coordinates of (100, 100) relative to
fixation target
1104 (in (X,Y) coordinate format), and if point 1128 has coordinates of (110,
105) in the
same format, then an image may be mapped from "normal" visual space to
"corrected" visual
space by mapping elements (e.g. pixels) of an image located at (100, 100) to
the new location
(110, 105). If all elements along pre-adjustment patterns 1110, 1130, 1202,
etc. (including
elements along the lines thereof) are mapped to the corresponding coordinates
along adjusted
patterns 1120, 1140, 1206, etc. (based on the above-described interpolated
lines), then the
"corrected" image may appear non-distorted to subject 802 along at least the
perceived areas
corresponding to adjusted patterns 1120, 1140, 1206, etc. (although those
areas may still
appear distorted if neighbouring areas are distorted, due to the complexities
of cognitive
processing).
[0151] Accordingly, a partial distortion map may be generated by mapping
coordinates of all
pre-adjustment patterns (such as patterns 1110, 1130, 1202, etc.) to the
corresponding
coordinates along adjusted patterns 1120, 1140, 1206, etc. However, in many
circumstances
it is desirable to generate a more detailed distortion map which also maps
locations not on
patterns 1110, 1130, 1202, etc. to locations not on adjusted patterns 1120,
1140, 1206, etc.
[0152] Method 770 (and in particular block 772) may involve mapping such
coordinates by
interpolation. For example, coordinates within distortion grid 1106 may be
mapped from
"normal" visual space to "corrected" visual space by applying bicubic
interpolation based on
the partial distortion map. Thus, each coordinate in "normal" visual space not
already
mapped to a coordinate in "corrected" visual space by the partial distortion
map may be
mapped to such a coordinate based on the mappings of the surrounding
coordinates (in
"normal" visual space). The mapped coordinates may be included in the
generated distortion
map. Other types of interpolation may be used. Preferably, two-dimensional
interpolation
methods may be used, such as bilinear interpolation, bicubic interpolation,
Bezier surfaces,
and/or other interpolation methods.
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[0153] Once a distortion map has been generated, method 700 (and therefore
method 770)
may optionally proceed to block 774, which involves validating the distortion
map generated
at block 772 to confirm that the generated distortion map is sufficiently
accurate; that is, to
confirm that images mapped from "normal" space to "corrected" space by
applying the
distortion map are perceived by subject 802 as substantially non-distorted.
This validation
may comprise displaying a validation pattern.
[0154] Figure 13A shows an example validation pattern 1300A having a fixation
target 1304
and grid lines 1302. Grid lines 1302 do not necessarily correspond to grid
lines 1012, 1022,
1032 of grid 1000A. An area 1306 has been distorted according to the
distortion map so that
all grid lines 1302 should be perceived as straight by subject 802. For
instance, validation
pattern 1300A may comprise a conventional Amsler grid which has been distorted
according
to the distortion map. Alternatively, or in addition, other validation
patterns such as other
patterns, photographs, or other images may be displayed to subject 802.
[0155] Block 774 may comprise varying the displayed validation patterns. For
example,
block 774 may comprise rotating the validation pattern, updating the distorted
area 1306 to
reflect any movement or other change in the underlying pattern. For example,
the Amsler grid
of Figure 13A may be rotated about fixation point 1304 through 90 . Figure 13B
shows an
example validation pattern 1300B which corresponds to the Amsler grid of
Figure 13A
rotated 45 , with the distortion map applied in area 1306 to distort the grid
lines of the rotated
grid according to the distortion map (which is not rotated with the validation
pattern). Other
validation patterns, such as those with a different degree of rotational
symmetry, may be
rotated more or less ¨ for instance, a validation pattern without rotational
symmetry may be
rotated through a full 360 . Reference pattern 1150 may be displayed during
the display of
validation patterns 1300A, 1300B, as described above.
[0156] As with blocks 734 and 736, computer system 811 may receive an input
indicating
whether the validation passes or fails ¨ e.g. if subject 802 perceives a
distortion during the
rotation of validation patterns 1300A, 1300B, then computer system 811 may be
provided
with an input which indicates failure. In response to receiving an input
indicating that the
validation passes, method 700 (and therefore method 770) may proceed to block
776.
Otherwise, if the computer system 811 receives an input indicating that the
validation fails,
block 774 may involve further refinement of the distortion map, as described
below.
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101571 If a portion of a validation pattern is perceived by subject 802 to be
distorted, a failure
indication may be provided to computer system 811. Subject 802 may then select
a region of
the validation pattern which appears distorted and make further adjustments.
For example,
Figure 14A shows an example perception 1400A of a selection display showing a
perceived
portion 1402 of validation pattern 1300B. Portion 1402 generally corresponds
to area 1306.
Area 1404 has distorted according to the distortion map (and so should,
ideally, appear non-
distorted), but subject 802 nevertheless perceives area 1404 as distorted.
Subject 802 may
select a point where a distortion is perceived. In this example, subject 802
has selected (e.g.
via input device 813) point 1406 in area 1404. Reference pattern 1150 (not
shown) and/or
fixation target 1106 (not shown) may continue to be displayed as described
above.
101581 In some embodiments, a guide pattern 1408 may be displayed to subject
802 to assist
subject 802 in selecting a point. For example, guide pattern 1408 may comprise
a crosshair
which has been distorted according to the distortion map. Guide pattern 1408
may be
displayed instead of, or in addition to, a user interface element such as a
mouse cursor.
Subject 802 may move the intersection of the crosshair to point 1406 (or to
any other point in
the distortion region) and select point 1406 using input device 813 or any
other means. Guide
pattern 1408 may be easier for subject 802 to identify than non-distorted user
interface
elements in areas where the distortion map is accurate. In some embodiments
and in some
circumstances, guide pattern 1408 may assist subject 802 in identifying areas
where the
distortion map is inaccurate by essentially providing a dynamic reference
pattern in areas of
interest. For example, as shown in Figure 14A, guide pattern 1408 is perceived
as distorted in
area 1404.
101591 In some embodiments, guide pattern 1408 comprises lines which are
thinner than the
lines of patterns 1110 or 1130. For example, guide pattern 1408 may comprise
lines which
are less than half as thick as the lines of patterns 1110 or 1130. Guide
pattern 1408 may also,
or alternatively, be in a different colour than the lines of patterns 1110 or
1130 and/or
validation pattern 1402.
[0160] Once point 1406 has been selected, a refinement display 1400B may be
displayed to
subject 802, as shown in Figure 14B. Refinement display 1400B may include
point 1406
and/or interpolated pattern 1418. Interpolated pattern 1418 may be
substantially similar to
guide pattern 1408. For example, interpolated pattern 1418 may comprise a
crosshair which
has been distorted according to the distortion map. The distortion map may
comprise grid
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CA 02880856 2015-02-03
lines 1410, which are not necessarily shown to subject 802. Grid lines 1410
may comprise
adjusted patterns 1120, 1140, 1206, etc. Anchor points 1412 may be placed at
the points
where interpolated pattern 1418 intersects with grid lines 1410. Interpolated
pattern 1418
may be derived from the distortion map, the interpolation of which is
described above. In
some embodiments, multiple interpolated patterns 1418 may be displayed to the
subject; each
interpolated pattern 1418 may be generated using a different interpolation
algorithm. For
example, one interpolated pattern 1418 may be generated using bilinear
interpolation, another
using bicubic interpolation, another using Bezier surfaces, and so on. The
subject may select
any one of the presented interpolated patterns 1418 for use by system 800; the
selected
interpolated pattern 1418 may be further refined as discussed below.
[0161] Figure 14C shows an example perception 1400C of display 1400B by
subject 802.
Grid lines 1420 correspond to distorted grid lines 1410. Although grid lines
1420 are not
necessarily visible to subject 802, if they were visible they would likely be
perceived to be
straight (since they correspond to previously-tested adjusted patterns 1120,
1140, 1206, etc.).
Perceived pattern 1428 is subject 802's perception of interpolated pattern
1418. Subject 802
perceives a distortion in perceived pattern 1428, as is clearly visible in
Figure 14C.
[0162] Subject 802 may be permitted to adjust the position of point 1406 so
that interpolated
pattern 1418 appears substantially non-distorted at least in the area bounded
by anchor points
1412. Adjustment of the position of point 1406 may be performed substantially
as described
above with reference to blocks 736, 754 and points 1128 and 1204. Further
points along
interpolated pattern 1418 between point 1406 and anchor points 1412 may be
defined and
may be adjusted by subject 802. In response to an adjustment of the position
of point 1406
(and/or other points) by subject 802, computer system 811 may reinterpolate
portions of
pattern 1418. In some embodiments, only the portions of pattern 1418 which are
bounded by
anchor points 1412 are reinterpolated (i.e. the effects of adjustments may be
confined to the
cell defined by grid lines 1410 in which the adjustment occurs).
[0163] The resulting adjusted and/or reinterpolated pattern may, optionally,
be tested
substantially as described with reference to block 756 and, if computer system
811 receives
an input indicating that the test is passed, the reinterpolated pattern may be
incorporated into
the distortion map as if it were an adjusted pattern 1120, 1140, 1206, etc.
Coordinates
surrounding the reinterpolated and/or adjusted pattern may be used as a basis
for further
reinterpolation of the distortion map. For example, coordinates not on the
reinterpolated
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CA 02880856 2015-02-03
pattern but within the area bounded by grid lines 1410 on which anchor points
1412 are
defined may have their mappings reinterpolated.
[0164] Validation pattern 1402 need not necessarily displayed to subject 802
during
refinement of interpolated pattern 1418. Reference pattern 1150 (not shown)
and/or fixation
target 1106 (not shown) may continue to be displayed as described above.
[0165] Once generated (and optionally validated and/or refmed), a distortion
map may be
used for various purposes. For example, a distortion map may be used to
generate corrective
optics, such as shaped lenses, GRIN lenses, and the like. As another example,
distortion maps
may be used to generate corrective displays, such as HUDs with eye trackers,
adaptive vision
goggles, video displays, and the like. As a further example, distortion maps
may be used to
generate quantitative measures of the physical displacement of the retina of a
subject 802,
which may assist in researching and/or treating metamorphopsia.
[0166] In some embodiments, after generating a distortion map at block 772
(and/or,
optionally, after validating the distortion map at block 774), method 700
proceeds to block
776, which involves generating a perception map. Unlike a distortion map,
which allows for a
mapping of "normal" images to "corrected" images which are perceived as
substantially non-
distorted by subject 802, a perception map enables a person with normal vision
to perceive
distortions substantially as they are perceived by metamorphopsia-affected
subject 802.
[0167] As illustrated, for example, by Figures 4B and 6A, a perception map is
not necessarily
the same as the geometric inverse of a distortion map. For instance, at the 0
index along axis
306, perceived line 412 is offset from the position of line 302 by -1 unit,
but the geometric
inverse of line 604 at the same location would result in an offset of -2
units.
[0168] The block 776 generation of a perception map may involve finding a
functional
inverse of the distortion map. That is, given a distortion map D: N ¨> C,
where N is the
"normal" visual space and C is the "corrected" visual space which complements
the distortion
of subject 802, and given that D (I) for an arbitrary image I is perceived by
subject 802 as
substantially non-distorted, then the perception map P: C ¨> N can be defined
as P (I) =
D-1(1), so that P(D(1)) = I. In other words, given a coordinate pair (x,y)
such that
D ((x, y)) = (x', y'), the perception map can be defined as P((x' , y')) = (x,
y).
CA 02880856 2015-02-03
[0169] In some embodiments, computer system 811 stores the distortion map at
least
partially as a lookup table, and generates the perception map by performing a
reverse lookup
and/or by reversing the lookup table.
[0170] Once generated, a perception map may be used for various purposes. For
example, a
perception map may be used as a tool by those who work with metamorphopsia-
affected
individuals as part of a treatment, rehabilitation, and/or the like. As
another example, a
perception map may be used to determine a quantitative measure of the visual
distortions
perceived by a subject 802, which may be relevant to assessing the overall
quality of vision
(and/or quality of life) of a subject 802. Quantitative measures may also, or
alternatively, be
generated from distortion maps; although a perception map may better
approximate the
subjective distortions perceived by a subject 802, it may be convenient or
desirable in some
circumstances to generate quantitative measures from a distortion map. System
811 may
provide one or more quantitative measures of the visual distortions perceived
by subject 802.
Certain methods of determining quantitative measures are discussed below, with
example
methods illustrated in Figures 15A, 15B, 15C, and 15D.
[0171] In some embodiments, system 811 may determine a quantitative measure
based on an
area of the distortion region identified by subject 802 (e.g. distortion
region 950, 960, and/or
970 of Figures 9J, 9K, and 9L). Figure 15A shows an example map 1500 (which,
as
discussed above, may be a perception map or a distortion map). Grid lines 1502
are shown
for the sake of clarity, although, as discussed above, the distortion and
perception maps may
be interpolated to provide a mapping which includes points not located on grid
lines 1502.
Subject 802 has identified boundary lines 1504 which contain the distortion
region, as
described above. A quantitative measure Q may be determined based on the area
of the
distortion region, e.g. so that distortion regions with larger areas may
correspond to
quantitative measures reflecting more severe distortions.
[0172] Due to the physiological nature of metamorphopsia, the actual
distortion perceived by
subject 802 is unlikely to be bounded by straight lines. Most commonly
(although not
universally), the actual distortion perceived by subject 802 is likely to be
better-approximated
by an ellipse than by a linearly bounded distortion region. System 811 may
determine an
ellipse 1506 which approximates the distortion region, and may determine a
quantitative
measure based on the area of ellipse 1506. In some embodiments, ellipse 1506
may be
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bounded by the distortion region identified by subject 802. For example, a
quantitative
measure Q may be determined according to the formula:
Q=f(mxaxb)
where a is the radius of the major axis of the ellipse, b is the radius of the
minor axis of the
ellipse, and f is a function which takes the area of the ellipse as an input.
f may be the
identity function.
[0173] In some embodiments, system 811 may determine the quantitative measure
based on
the severity of displacement of all or part of the distorted region. Figures
15B, 15C and 15D
show an expanded view of a portion of example map 1500, namely the portion in
the vicinity
of the distortion region. In some embodiments, system 811 selects a line 1514
as displayed at
display 810 (i.e. prior to being perceived and distorted) passing through the
distortion region.
Line 1512 is the perception of line 1514 by subject 802; as shown, line 1512
is distorted so
that various points therein are displaced relative to line 1514. System 811
may determine a
quantitative measure based on the severity of the displacement caused by this
distortion.
[0174] In some embodiments, the severity of displacement may be determined
based on an
area displaced. Figure 15B illustrates an example method for determining a
severity of
displacement based on an area displaced. System 811 may determine the severity
(and thus
the quantitative measure Q) based on the area 1516 between original line 1514
and distorted
line 1512. Such an area may be approximated, for example, by summing the
displacement of
indicia along line 1512 relative to line 1514, by integrating along the curve
of line 1512 (e.g.
using numerical integration methods, such as Simpson's rule, and/or symbolic
integration
methods) to determine the approximate area between lines 1512 and 1514, and/or
by other
methods. For example, a quantitative measure Q may be determined according to
the
formula:
Q = f (I Ig(x)Idx)
a
where a and b are points which bound the distorted portion of the linear cross-
section (e.g. a
and b may be on opposing sides of the boundary of the distorted region, on
opposing sides of
display 1202B, or elsewhere), g(x) is the displacement of point x on the
linear cross-section,
37
CA 02880856 2015-02-03
and f is a function which takes the area of displacement as an input. f may be
the identity
function.
101751 As another example, system 811 may determine the severity of the
displacement
based on a linear displacement of a particular point. Figure 15C illustrates
an example
method for determining a severity of displacement based on the displacement of
a point 1522
from its original (pre-distortion) position 1524. For example, the severity of
displacement at
point 1522 may be determined based on the magnitude of the displacement
distance 1526
from original position 1524 to the current position of point 1522. For
example, a quantitative
measure Q may be determined according to the formula:
Q = f (Iga(x) ¨ gb(x)1)
where ga(x) is the position of a point x after applying the distortion map, g
b(x) is the
position of the same point x in the original image (i.e. before applying the
distortion map),
and f is a function which takes the displacement of a point as an input. f may
be the identity
function. '
101761 As yet another example, system 811 may determine the severity of the
displacement
at a particular point based on a local change in displacement. Figure 15D
illustrates an
example method for determining a severity of displacement based on the local
change in
displacement of point 1522. The change in displacement at a particular point
(e.g. point 1522)
in a distorted image relative to nearby points can be a reasonable predictor
of the severity of a
subject's perceived distortion. That is, even if a point is severely
displaced, if all surrounding
points are similarly displaced then the subject may perceived relatively less
distortion at that
point. System 811 may determine a gradient (and/or an approximation thereof)
over the
distortion region, for example using vector analysis and/or numerical analysis
methods. The
gradient at a particular point is the rate of change in the point's
displacement (as measured
above) relative to nearby points, and/or instantaneously at that point. A
quantitative measure
Q for a particular point 1522 may be determined based on the gradient.
[0177] It may be convenient or otherwise desirable to approximate the local
change in
distortion for a particular point without necessarily conducting vector
analysis on each point.
The rate of change in displacement at a particular point 1522 (i.e. the
approximated value of
the gradient at point 1522) may be approximated based on the displacement
distance 1526
(discussed above) and the inner distance 1536 between point 1522 and the
boundary of the
38
CA 02880856 2015-02-03
distortion region (e.g. at point 1532). Inner distance 1536 may be the
distance from original
position 1524 to boundary point 1532, the distance from the projection of
point 1522 onto
line 1514 to boundary point 1532, and/or some other distance which relates
point 1522 to the
boundary of the distortion region. Boundary point 1532 is the closest point to
point 1522 on
both the boundary of the distortion region and on line 1514 (or, equivalently
in this example,
line 1512). A quantitative measure may be determined by scaling the
displacement distance
1526 by inner distance 1536 so that, if the displacement distances of points
along line 1512
stay the same as their inner distances increase, the quantitative measure will
reflect
decreasing severity rather than uniform severity.
[0178] For example, a quantitative measure Q may be determined according to
the formula:
Q = f (Mx) ¨ gb(x),
d (x)
where g a (x) is the position of point x after applying the distortion map, g
b (x) is the position
of point x in the original image (i.e. before applying the distortion map), d
(x) is the distance
from the point x to the closest point on the boundary of the distortion region
(e.g. inner
distance 1536), and f is a function which takes the displacement of a point as
an input. f may
be the identity function.
[0179] In some embodiments, a quantitative measure Q may be based on the
severity of the
displacement of one or more points. For example, given a set of points P in
the distortion
region, the quantitative measure Q may be determined based on a statistical
measure of the
linear displacement and/or gradient of the points in P, such as (for example)
the mean,
median, mode, maximum, or other measure. Multiple quantitative measures Q may
be
determined by system 811; for instance, each point in P may be associated with
its own
quantitative measure, from which a "heat map" may be generated to assist in
assessment of
the severity of distortion in specific regions of the subject's vision.
Interpretation of Terms
[0180] Unless the context clearly requires otherwise, throughout the
description and the
claims:
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CA 02880856 2015-02-03
= "comprise", "comprising", and the like are to be construed in an
inclusive sense, as
opposed to an exclusive or exhaustive sense; that is to say, in the sense of
"including,
but not limited to";
= "connected", "coupled", or any variant thereof, means any connection or
coupling,
either direct or indirect, between two or more elements; the coupling or
connection
between the elements can be physical, logical, or a combination thereof;
= "herein", "above", "below", and words of similar import, when used to
describe this
specification, shall refer to this specification as a whole, and not to any
particular
portions of this specification;
= "or", in reference to a list of two or more items, covers all of the
following
interpretations of the word: any of the items in the list, all of the items in
the list, and
any combination of the items in the list;
= the singular forms "a", "an", and "the" also include the meaning of any
appropriate
plural forms.
[0181] Words that indicate directions such as "vertical", "transverse",
"horizontal",
"upward", "downward", "forward", "backward", "inward", "outward", "vertical",
"transverse", "left", "right", "front", "back", "top", "bottom", "below",
"above", "under",
and the like, used in this description and any accompanying claims (where
present), depend
on the specific orientation of the apparatus described and illustrated. The
subject matter
described herein may assume various alternative orientations. Accordingly,
these directional
terms are not strictly defined and should not be interpreted narrowly.
[0182] Specific examples of systems, methods and apparatus have been described
herein for
purposes of illustration. These are only examples. The technology provided
herein can be
applied to systems other than the example systems described above. Many
alterations,
modifications, additions, omissions, and permutations are possible within the
practice of this
invention. This invention includes variations on described embodiments that
would be
apparent to the skilled addressee, including variations obtained by: replacing
features,
elements and/or acts with equivalent features, elements and/or acts; mixing
and matching of
features, elements and/or acts from different embodiments; combining features,
elements
and/or acts from embodiments as described herein with features, elements
and/or acts of other
CA 02880856 2015-02-03
technology; and/or omitting combining features, elements and/or acts from
described
embodiments.
[0183] Computer system 811 and/or components thereof (including, for example,
one or
more processors) may comprise hardware, software, firmware or any combination
thereof.
Computer system 811 may comprise one or more microprocessors, digital signal
processors,
graphics processors, field programmable gate arrays, and/or the like.
Components of
computer system 811 may be combined or subdivided, and components of computer
system
811 may comprise sub-components shared with other components of computer
system 811.
Components of computer system 811 may be physically remote from one another.
[0184] Where a component is referred to above (e.g., a system, display,
processor, etc.),
unless otherwise indicated, reference to that component (including a reference
to a "means")
should be interpreted as including as equivalents of that component any
component which
performs the function of the described component (i.e., that is functionally
equivalent),
including components which are not structurally equivalent to the disclosed
structure which
performs the function in the illustrated exemplary embodiments of the
invention.
[0185] It is therefore intended that the following appended claims and claims
hereafter
introduced are interpreted to include all such modifications, permutations,
additions,
omissions, and sub-combinations as may reasonably be inferred. The scope of
the claims
should not be limited by the preferred embodiments set forth in the examples,
but should be
given the broadest interpretation consistent with the description as a whole.
41
