U.S. patent application number 14/324629 was filed with the patent office on 2016-01-07 for system for measuring visual fixation disparity.
The applicant listed for this patent is eyeBrain Medical, Inc.. Invention is credited to John Merril Davis, III, Jeffrey P. Krall, Vance Thompson.
Application Number | 20160000317 14/324629 |
Document ID | / |
Family ID | 55016128 |
Filed Date | 2016-01-07 |
United States Patent
Application |
20160000317 |
Kind Code |
A1 |
Krall; Jeffrey P. ; et
al. |
January 7, 2016 |
SYSTEM FOR MEASURING VISUAL FIXATION DISPARITY
Abstract
There is disclosed herein a system for measuring visual fixation
disparity comprising a display apparatus for presenting
stereoscopic visual content to a patient. A sensing apparatus
tracks eye movement of the patient. A controller controls the
display apparatus to stereoscopically display a central image
target alternately to a left eye and a right eye of the patient and
tracking eye movement for a period of time as the central image
target is alternated between the left eye and the right eye, and
incrementally relocating the central image target left and right
images until the patient perceives the left and right images to be
physically coincident.
Inventors: |
Krall; Jeffrey P.;
(Mitchell, SD) ; Thompson; Vance; (Sioux Falls,
SD) ; Davis, III; John Merril; (Midlothian,
VA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
eyeBrain Medical, Inc. |
San Diego |
CA |
US |
|
|
Family ID: |
55016128 |
Appl. No.: |
14/324629 |
Filed: |
July 7, 2014 |
Current U.S.
Class: |
351/240 |
Current CPC
Class: |
G06F 3/013 20130101;
A61B 3/08 20130101; H04N 13/383 20180501; H04N 13/341 20180501;
A61B 3/113 20130101; G02B 30/24 20200101 |
International
Class: |
A61B 3/08 20060101
A61B003/08 |
Claims
1. A system for measuring visual fixation disparity comprising: a
display apparatus for presenting stereoscopic visual content to a
patient; a sensing apparatus for monitoring central vision of the
patient; a controller for controlling the display apparatus to
stereoscopically display a smoothly moving peripheral target with a
static central image target to isolate central vision from
peripheral vision of the patient and monitor the central vision of
the patient.
2. The system for measuring visual fixation disparity of claim 1
wherein the display apparatus comprises a stereo LCD display and
synchronously driven LCD shutters.
3. The system for measuring visual fixation disparity of claim 1
wherein the display apparatus comprises a polarized light stereo
display and matching polarized eye filters.
4. The system for measuring visual fixation disparity of claim 1
wherein the sensing apparatus comprises left and right image
capture devices for tracking pupil position of the patients left
and right eyes, respectively.
5. The system for measuring visual fixation disparity of claim 4
wherein the sensing apparatus is selectively adjustable to space
the left and right image capture devices corresponding to the
patient's pupillary distance.
6. The system for measuring visual fixation disparity of claim 1
wherein the controller controls the display apparatus to
stereoscopically display a central image target alternately to a
left eye and a right eye of the patient and tracking eye movement
for a period of time as the central image target is alternated
between the left eye and the right eye, and incrementally
relocating the central image target left and right images until the
patient perceives the left and right images to be physically
coincident.
7. The system for measuring visual fixation disparity of claim 1
wherein the peripheral target and the central image target are
stereoscopically consistent with each other.
8. The system for measuring visual fixation disparity of claim 1
wherein the peripheral target and the central image target are
intentionally stereoscopically inconsistent with each other.
9. The system for measuring visual fixation disparity of claim 1
wherein the controller controls the display apparatus to
stereoscopically display a plurality of smoothly moving peripheral
targets with the static central image target.
10. A system for measuring visual fixation disparity comprising: a
display apparatus for presenting stereoscopic visual content to a
patient; a sensing apparatus for tracking eye movement of the
patient; a controller for controlling the display apparatus to
stereoscopically display a central image target alternately to a
left eye and a right eye of the patient and tracking eye movement
for a period of time as the central image target is alternated
between the left eye and the right eye, and incrementally
relocating the central image target left and right images until the
patient perceives the left and right images to be physically
coincident.
11. The system for measuring visual fixation disparity of claim 10
wherein the display apparatus comprises a stereo LCD display and
synchronously driven LCD shutters.
12. The system for measuring visual fixation disparity of claim 10
wherein the sensing apparatus comprises left and right image
capture devices for tracking pupil position of the patients left
and right eyes, respectively.
13. The system for measuring visual fixation disparity of claim 12
wherein the sensing apparatus is selectively adjustable to space
the left and right image capture devices corresponding to the
patient's pupillary distance.
14. The system for measuring visual fixation disparity of claim 10
wherein the controller controls the display apparatus to
stereoscopically display a peripheral target stereoscopically
consistent with the static central image target to isolate central
vision from peripheral vision of the patient and monitor the
central vision of the patient.
15. The system for measuring visual fixation disparity of claim 10
wherein the controller controls the display apparatus to
stereoscopically display a moving peripheral target
stereoscopically consistent with the static central image target to
isolate central vision from peripheral vision of the patient and
monitor the central vision of the patient.
16. The system for measuring visual fixation disparity of claim 10
wherein the controller controls the display apparatus to
stereoscopically display a peripheral target intentionally
stereoscopically inconsistent with the static central image target
to isolate central vision from peripheral vision of the patient and
monitor the central vision of the patient.
17. The system for measuring visual fixation disparity of claim 10
wherein the controller controls the display apparatus to
stereoscopically display a moving peripheral target intentionally
stereoscopically inconsistent with the static central image target
to isolate central vision from peripheral vision of the patient and
monitor the central vision of the patient.
18. The system for measuring visual fixation disparity of claim 10
wherein the controller determines eye movement for each eye between
a time that the central image target is not visible to each eye and
a time that the central image target is visible to each eye.
19. The system for measuring visual fixation disparity of claim 18
wherein the controller relocates the central image target until eye
movement is less than a select amount.
20. The system for measuring visual fixation disparity of claim 18
wherein the controller relocates the central image target until
there is substantially no eye movement.
21. The system for measuring visual fixation disparity of claim 18
wherein the controller monitors rotation of the eyes when the
controller tracks eye movement.
22. The system for measuring visual fixation disparity of claim 18
wherein the controller compares eye tracking images at select
intervals to measure slow drifts of the eyes.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not Applicable.
FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable.
MICROFICHE/COPYRIGHT REFERENCE
[0003] Not Applicable.
FIELD
[0004] This application relates to vision correction and, more
particularly, to measuring fixation disparity of the visual
system.
BACKGROUND
[0005] The optical system of the human eye uses numerous muscles as
well as central and peripheral cues while focusing on targets both
near and far. There are many responses involved in changing focus
from distant to near as well as fixating on a target at a set
distance.
[0006] When our eyes are working together and are directed at a
target greater than twenty feet from our eyes they will appear to
be parallel with each other and we deem this binocularity. If both
eyes are looking at a target closer than twenty feet our eyes may
not look parallel but we a still have binocular vision as long as
the line of sight of each eye is pointing directly at the target of
regard. If binocularity is canceled by interrupting the vision of
one eye or the other the eyes often rotate along X, Y, &
Z-axis. The movement and rotation of the eye that is covered
compared to the movement of the eye that is uncovered may be
different, but measurable. In general terms the change in position
or movement of the eyes once vision is interrupted, ending
binocularity, is often deemed a heterophoria. It is also possible
to measure the torsional rotation and movement along the X, Y,
& Z axis of the eye by not interrupting one eye or disrupting
binocularity. This may be done by altering the position of
peripheral binocular targets located in a relationship to the
central binocular targets.
[0007] Our proprioceptive system, or what we often call our "sixth
sense", is the sensory feedback mechanism for motor control and
posture. It gives us unconscious feedback internally. Our
proprioceptive system is composed of sensory neurons located in our
inner ear and stretch receptors located in our muscles and
supporting ligaments.
[0008] In our skeletal muscles these proprioceptive receptors have
a load compensating mechanism. For example: imagine standing with
eyes closed and arms extended outward. Now imagine someone starting
to load one book after another on your hands. As you feel the
weight of the books increase, you exert more force in order to keep
the books from falling to the ground. When maximum effort is
reached the books will fall from your hands. You do not need your
eyes to sense the weight.
[0009] There are anatomically similar proprioceptive receptors in
our ocular muscles but these receptors do not have a load
compensating mechanism and do not mediate conscious eye position.
This is understandable because there is a constant mechanical load
on all the extraocular muscles and no load compensating mechanism
is required.
[0010] Our extraocular muscles have proprioceptive receptors that
constantly give feedback to the location of each eye. When we
choose to look at something our brain takes the image from each eye
and moves our extraocular muscles to exactly line up to the target.
If this did not happen you would have blurred vision one eye
pointing at one target and the other eye pointing at a different
target.
[0011] You can choose where you want to look but then your
autonomic nervous system takes the image from each eye and sends a
signal to your extraocular muscles to line each eye up perfectly at
that target. After the movement of each eye independently to line
up the target the proprioceptive receptors in your extraocular
muscles send the signal back to brain as to the position of where
each eyes has been moved to. This proprioceptive feedback is
necessary to close the loop between where the brain told the eyes
to move and where the eyes are currently located. The brain needs
to know the position of each eye so that when you decide to look at
the next target your brain knows how much to move each eye in order
to line up to the next target.
[0012] This proprioceptive feedback is critical for coordinating
the movements between our eyes, seeing a single clear image, along
with many other functions. We know that this proprioceptive
feedback from our extraocular muscles sends its signal via the
trigeminal nerve, which is a nerve in our head responsible for pain
sensation in our sinuses, extraocular muscle tissue, and jaw.
[0013] Many people who suffer from chronic headaches, asthenopia
associated with near work, asthenopia associated with viewing
distance targets, stiff neck and shoulder muscles, and dry eyes are
the consequence of the extra ocular muscles proprioceptive sensory
feedback mechanism stimulating the trigeminal nerve. From clinical
study with chronic headache patients we have learned that changing
this feedback loop can alter and often alleviate headache pain.
This can be done by measuring proprioceptive disparity or more
generally visual fixation disparity. Proprioceptive disparity is
the imbalance between where the eyes are consciously focused and
the nonvisual perception of where the object is located in space.
This often varies with distance.
[0014] Testing and synchronizing the proprioceptive feedback
between each extraocular muscle requires isolating our central
vision from our peripheral vision. Our central vision sustains less
than 1.degree. of arc and is responsible for detailed vision
located within the area of our retina called our fovea. Targets
seen in the fovea are controlled by slow smooth pursuits eye
movements. Targets outside of our fovea and in our peripheral
vision are controlled by quick saccadic eye movements. Anatomically
we know that pursuits and saccadic eye movements are coordinated in
our brain from different locations.
[0015] The use of electronic image capture devices to observe and
quantify the movement of the human eye is a mature technology known
as "eye tracking". Some applications of eye tracking include
military equipment for pilots, sophisticated 3-D virtual reality
environments, and medical analysis.
[0016] Good quality stereo 3-D display technology is relatively new
to consumer products, but has been available for professional
applications for many years. A variety of 3-D display technologies
have been developed which endeavor to provide the viewer with two
visual images, one for each eye, which differ slightly in their
content so as to present all targets in the visual field with their
mathematically correct parallax according to distance from the
viewer. The oldest movie technology used different glasses with
colored filters for each eye. This was crude and unrealistic.
Current technology for movies uses glasses with either passive
polarized filters or active-shutter electronics. New technologies
for single user displays are autostereoscopic (i.e., not requiring
glasses) and incorporate lenticular lenses or parallax barriers to
provide separate images for each eye.
[0017] This application is directed to improvements in testing
proprioceptive feedback.
SUMMARY
[0018] This application relates to a system for measuring visual
fixation disparity which uses a stereoscopic display in conjunction
with eye tracking.
[0019] There is disclosed in accordance with one aspect a system
for measuring visual fixation disparity comprising a display
apparatus for presenting stereoscopic visual content to a patient.
A sensing apparatus monitors central vision of the patient. A
controller controls the display apparatus to stereoscopically
display a smoothly moving peripheral target with a static central
image target to isolate central vision from peripheral vision of
the patient and monitor the central vision of the patient.
[0020] It is a feature that the display apparatus comprises a
stereo LCD display and synchronously driven LCD shutters.
[0021] It is another feature that the display apparatus comprises a
polarized light stereo display and matching polarized eye
filters.
[0022] It is a further feature that the sensing apparatus comprises
left and right image capture devices for tracking pupil position of
the patient's left and right eyes, respectively. The sensing
apparatus may be selectively adjustable to space the left and right
image capture devices corresponding to the patient's pupillary
distance.
[0023] It is still another feature that the controller controls the
display apparatus to stereoscopically display a central image
target alternately to a left eye and a right eye of the patient and
tracking eye movement for a period of time as the central image
target is alternated between the left eye and the right eye, and
incrementally relocating the central image target left and right
images until the patient perceives the left and right images to be
physically coincident.
[0024] It is still another feature that the peripheral target and
the central image target are stereoscopically consistent with each
other.
[0025] It is yet a further feature that the peripheral target and
the central image target are intentionally stereoscopically
inconsistent with each other.
[0026] It is still a further feature that the controller controls
the display apparatus to stereoscopically display a plurality of
smoothly moving peripheral targets with the static central image
target.
[0027] There is also disclosed herein a system for measuring visual
fixation disparity comprising a display apparatus for presenting
stereoscopic visual content to a patient. A sensing apparatus
tracks eye movement of the patient. A controller controls the
display apparatus to stereoscopically display a central image
target alternately to a left eye and a right eye of the patient and
tracking eye movement for a period of time as the central image
target is alternated between the left eye and the right eye, and
incrementally relocating the central image target left and right
images until the patient perceives the left and right images to be
physically coincident.
[0028] In one aspect the controller controls the display apparatus
to stereoscopically display a peripheral target stereoscopically
consistent with the static central image target to isolate central
vision from peripheral vision of the patient and monitor the
central vision of the patient.
[0029] In accordance with another aspect, the controller controls
the display apparatus to stereoscopically display a moving
peripheral target stereoscopically consistent with the static
central image target to isolate central vision from peripheral
vision of the patient and monitor the central vision of the
patient.
[0030] In yet another aspect, the controller controls the display
apparatus to stereoscopically display a peripheral target
intentionally stereoscopically inconsistent with the static central
image target to isolate central vision from peripheral vision of
the patient and monitor the central vision of the patient.
[0031] In yet another aspect, the controller controls the display
apparatus to stereoscopically display a moving peripheral target
intentionally stereoscopically inconsistent with the static central
image target to isolate central vision from peripheral vision of
the patient and monitor the central vision of the patient.
[0032] It is a feature that the controller determines eye movement
for each eye between a time that the central image target is not
visible to each eye and a time that the central image target is
visible to each eye. The controller may relocate the central image
target until eye movement is less than a select amount, or until
there is substantially no eye movement.
[0033] Other features and advantages will be apparent from a review
of the entire specification, including the appended claims and
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a perspective view of a system for measuring
visual fixation disparity;
[0035] FIG. 2 is a partial front elevation view of the system of
FIG. 1;
[0036] FIG. 3 is a view similar to FIG. 2 with an acrylic lens
removed;
[0037] FIG. 4 is a block diagram for the system of FIG. 1;
[0038] FIG. 5 is a block diagram for the image capture device of
FIG. 4;
[0039] FIG. 6 is a perspective view of the components of the system
of FIG. 1 illustrating visual aspects thereof;
[0040] FIG. 7 is a flow diagram illustrating operation of the
system of FIG. 1;
[0041] FIG. 8 is a flow diagram illustrating operation of a central
monocular test of FIG. 7;
[0042] FIGS. 9A and 9B illustrate initial alternating stereo
display images with the central monocular test of FIG. 8;
[0043] FIGS. 10A and 10B illustrate final alternating stereo
display images with the central monocular test of FIG. 8;
[0044] FIG. 11 is a graphic illustrating patient perception during
the central monocular test of FIG. 8;
[0045] FIG. 12 is a flow diagram illustrating operation of a
central peripheral test of FIG. 7;
[0046] FIGS. 13A and 13B illustrate initial alternating stereo
display images with the central peripheral test of FIG. 12;
[0047] FIGS. 14A and 14B illustrate final alternating stereo
display images with the central peripheral test of FIG. 12;
[0048] FIG. 15 is a graphic illustrating patient perception during
the central peripheral test of FIG. 12;
[0049] FIG. 16 is a flow diagram illustrating operation of an EXO
peripheral test of FIG. 7;
[0050] FIGS. 17A and 17B illustrate initial alternating stereo
display images with the EXO peripheral test of FIG. 16;
[0051] FIGS. 18A and 18B illustrate final alternating stereo
display images with the EXO peripheral test of FIG. 16;
[0052] FIG. 19 is a graphic illustrating patient perception during
the EXO peripheral test of FIG. 16;
[0053] FIG. 20 illustrates an alternative display for peripheral
targets with the central peripheral test;
[0054] FIG. 21 illustrates the patient's perspective with the
peripheral targets of FIG. 20 and illustrating movement of the
targets; and
[0055] FIG. 22 illustrates an alternative display for the EXO
peripheral test.
DETAILED DESCRIPTION
[0056] The measurement of visual fixation disparity, including
proprioceptive disparity, for diagnosis and subsequent refractive
lens treatment requires that the fixation disparity be measured
with a repeatable accuracy that is independent both of the
patient's subjective feedback and of the administering medical
practitioner's technique. Problems exist with prior methods and
systems for accomplishing appropriate measurement due to both of
these factors.
[0057] The systems and methodology described herein allow medical
professionals to accurately measure patient visual fixation
disparity. To this end, the measurements are made in a fully
automated process which requires the patient's cooperation, not the
patient's interpretation of the visual presentation. The
combination of the system and its automated functionality provides
unique solutions to this problem.
[0058] The system described herein presents stereoscopic visual
content to the patient. Continuous eye movement is a characteristic
of human vision. The brain must necessarily quickly correlate
fragments of moving images from both eyes to achieve a 3-D mental
model of the body and its position in movement relative to its
surroundings. At the same time, the patient's central vision must
be able to employ its superior acuity to recognize targets and
determine their position relative to the body. Catching a ball
while running is an extreme example of this human ability. The
achievement of neurological stereoscopic fusion in the brain of the
patient simultaneously of both peripheral and central images is
necessary as one part of the measurement process. In accordance
with one aspect, the system disclosed herein uses a synthesized
stereoscopic 3-D image incorporating a smoothly moving peripheral
image target combined with a static but central image target that
forms an effective visually compelling methodology to accomplish
this aspect.
[0059] In accordance with another aspect, eye tracking is used in
the context of the stereoscopic display of central and peripheral
images. In a portion of the measurement process, the peripheral
image is maintained while the left and right eye images of the
central vision target are precisely displaced from their
mathematically correct positions by an amount which may be
expressed in optical diopters of prism. The central image is
"flashed" to help "break" the fusion in the patient's brain and the
patient's eyes are closely watched for movement by image capture
devices. The presence of eye movement correlating with the
appearance of the central image target indicates when the patient
perceives two distinct targets rather than one. This allows for
interpreting the patient's degree of fusion of the central vision
target in the context of conflicting information from the patient's
fusion of the moving peripheral target.
[0060] A system is disclosed herein which implements the two novel
aspects described above. An illustrative hardware platform used to
implement the visual content consists of standard 3-D stereo
display technology in the form of a stereo-capable projector or
display monitor and video electronics capable of supporting a pair
of active-shutter glasses or a polarized light stereo display and
matching polarized eye filters. Without loss of generality, the
platform could also be equipment capable of autostereoscopy such as
those which incorporate lenticular lenses or a parallax barrier, or
combinations of two displays with half mirrors. A standard computer
with a 3-D stereo-capable video graphics card and display monitor
or projector, which are well known in the art, use conventional
software applications to create the simple stereo display images.
The software applications could be, for example, OpenGL or
DirectX.RTM. (a registered trademark of Microsoft Corporation). The
eye tracking function can be implemented with a pair of image
capture devices and conventional professional grade image capture
video hardware and image correlating software. Although other
implementations may be desirable, the particular implementation of
the hardware disclosed herein is not required for the invention as
defined by the claims herein.
[0061] Referring initially to FIG. 1, an image capture device 100
is illustrated forming part of a system 102 for measuring visual
fixation disparity, see FIG. 4. The image capture device 100
comprises a housing base 104 and housing cover 106 to define an
interior space 108. In the illustrated embodiment, the base 104 and
cover 106 define a parallelepiped shaped housing, although the
particular shape is not critical.
[0062] The cover 106 includes a front wall 110, see also FIG. 2,
including a patient positioning apparatus 112. The positioning
apparatus 112 comprises a chin support 114 which is selectively
movable up and down via a front wall slot 116 to appropriately
position the patient's eyes relative to a translucent black acrylic
lens 118 covering a front opening 120, see FIG. 3. Generally
rectangular side shields 122 and 124 extend outwardly from the
front wall 110 on either side of the opening 120. A forehead rest
126 extends outwardly from the front wall 110 between the side
plates 122 and 124. The shields 122 and 124 and the forehead rest
126 prevent ambient light from interfering with the operation. A
conventional lens holder 128 is optionally mounted to the front
wall 110 using apertures 130, see FIG. 3, for holding ophthalmic
lenses equivalent to a patient's eyeglass prescription.
[0063] Referring to FIG. 3, the front wall 110 is illustrated with
the acrylic lens 118, see FIG. 2, removed to show a printed circuit
board 132 mounted across the opening 120. The printed circuit board
132 includes a left LCD shutter 134L and a right LCD shutter 134R.
Each of the shutters 134L and 134R is surrounded by eight infrared
LEDs 136. As described below, the user's chin is rested on the chin
support 114 which is then raised or lowered to appropriately
position the patient so that the patient's left eye is looking
through the left LCD shutter 134L and the patient's right eye is
looking through the right LCD shutter 134R. The infrared LEDs 136
are illuminated to illuminate each eye for tracking eye movement,
as described below.
[0064] Referring to FIG. 4, a block diagram illustrates the
components of the system 102 for measuring visual fixation
disparity using the image capture device 100. The system uses a
conventional personal computer 140. The computer 140 includes a
programmed processor and memory storing programs and data for use
during the measurement of visual fixation disparity. The internal
components of the computer 140 are well-known and are therefore not
described in detail herein. The computer 140 may use any operating
system, as necessary or desired, running an application program for
the measurement of visual fixation disparity, as described
herein.
[0065] The computer 140 includes a stereo video card 142 including
DVI ports 144 for connection via cables 146 and 148 to an operator
LCD monitor 150 and the image capture device 100, respectively. A
3-D synch port 152 is provided for connection via a synch cable 154
to the image capture device 100. A conventional USB port 156 is
provided for connection via a USB cable 158 to the image capture
device. A keyboard 160 and mouse 162 are connected via respective
ports 164 and 166 to the computer 140. The image capture device 100
is also connected via a monitor AC cable 168 and a power supply AC
cable 170 to a 120 volt AC source (not shown). A power cable for
the computer 140 is not illustrated. Also, the computer 140 may be
connected via network cable or wirelessly to other computers or
servers, or the like, as necessary or desired.
[0066] The implementation of the hardware external to the image
capture device 100 and shown in FIG. 4 is by way of example only
and is not intended to be limiting. The computer 140 may take any
known form, as may the peripheral devices such as the monitor 150,
keyboard 160, and mouse 162. Other peripheral devices and memory
devices and the like, may also be used.
[0067] Referring to FIG. 5, a block diagram illustrates the
components in the housing forming the image capture device 100. A
microcontroller 172 is connected to the 3-D stereo synch cable 154
and the USB cable 158 as well as the AC power cable 170. The
microcontroller 172 comprises a programmed processor and related
memory for controlling operation of the image capture device 100
and communicates with the computer 140. As will be apparent, the
microcontroller functionality could be implemented in the computer
140, or vice versa. A patient stereo LCD monitor 174 is connected
to the DVI video cable 148 and the monitor AC power cord 168. A
multi-function electrical cable 176 connects the microcontroller
172 to the circuit board 132 for controlling the left LCD shutter
134L and the right LCD shutter 134R and the LEDs 136. A first
camera line 178L connects the microcontroller 172 to a left camera
180L and a right camera line 178R connects the microcontroller 172
to a right camera 180R. The microcontroller 172 is connected to a
left stepper motor 182L and a right stepper motor 182R and
associated limit switches 184L and 184R. Finally, the
microcontroller 172 is connected to a chin stepper motor 186 and an
associated upper limit switch 188 and lower limit switch 190. The
chin stepper motor 186 controls position of an actuator (not shown)
connected through the slot 116 to the chin support 114 for raising
and lowering the same.
[0068] FIG. 6 schematically illustrates the functional relationship
of the devices in the block diagram of FIG. 5, ignoring the
microcontroller 172 and related circuitry, within the housing space
108. Mounting structure for the various components is not shown and
does not itself form part of the invention. The stereo LCD monitor
174 is mounted parallel to the front wall 110 a select distance
therefrom. A left L bracket 192L and a right L bracket 192R are
movably mounted, in any known manner, to the base 104 between the
front wall 110 and the patient monitor 174. The left bracket 192L
includes a horizontal part 194L supporting the left camera 180L,
and an upstanding vertical part 196L supporting a lens 198L. The
left bracket 192L is movable from side to side under control of the
left stepper 182L. Similarly, the right bracket 192R includes a
horizontal part 194R supporting the right camera 180R and an
upstanding vertical part 196R supporting a right lens 198R. The
right bracket 192R is movable from side to side under control of
the right stepper 182R. A splitting mirror 200 is mounted at a
45.degree. angle above the cameras 180L and 180R and between the
front plate 110 and the LCD monitor 174. The patient monitor 174 is
mounted about one to two feet from the front wall 110. The lenses
198L and 198R have about 1/2 diopter power so that the images on
the patient monitor 174 appear to be about twenty feet from the
front wall 110.
[0069] With the illustrated hardware, the patient's left eye 202L
looks through the left LCD shutter 134L, via a line of sight 204L,
and then through the left lens 198L and the splitting mirror 200 to
the LCD display 174. Also, the splitting mirror 200 reflects the
image from the user's left eye 202L to the camera 180L. The left
eye 202L, being illuminated by the infrared LEDs 136 is visible to
the left camera 180L. Similarly, the patient's right eye 202R has a
line of sight 204R through the right LCD shutter 134R, the right
lens 198R, and the splitting mirror 200 which splits the line of
sight to the LCD monitor 174 and the right camera 180R. The right
eye 202R, being illuminated by the infrared LEDs 136 is visible to
the right camera 180R. As such, the eyes 202L and 202R see the
display on the LCD monitor 174, while the cameras 180L and 180R and
imaging software track movement of the pupils of the eyes 202L and
202R, respectively.
[0070] The system 102 measures the proprioceptive disparity, or
more generally fixation disparity, between where the eyes are
focused at compared to where they automatically want to converge
to. The image capture device 100 is used to automatically determine
the alignment between the line of sites of the right and left eye.
This system will also measure: high frequency tremors, pursuit eye
movements, saccadic eye movements, irregular movements, slow
drifts, optkinetic reflexes, torsional rotation of the eye and the
disparity between our sense of sight and our proprioceptive
feedback mechanism. This instrument can measure one eye at a time
and/or both eyes at the same time. Its enhanced technology isolates
separately the central foveal targets from the peripheral targets
and will align the central and peripheral targets together. This
system is intended to be used to detect a misalignment between the
right and left eye on any human whether they're wearing contacts,
glasses or have had surgery in either eye. It may be a
self-contained or a portable device either hand held, or table
mounted. The device will use a series of targets that simulate
optical infinity and/or near targets of various size shape and
color.
[0071] More particularly, the system 102 is used to measure visual
fixation disparity using proprioceptive feedback. This is done by
isolating the central vision from the peripheral vision of each eye
and using an eye tracking system to capture and monitor the
movements of each eye independently. The computer 140 calculates
the movements using data from the image capture device 100. This is
accomplished using one or more of five different tests. A first
test comprises a central monocular test which measures how the
central vision of each eye aligns when peripheral vision is not
stimulated. The second test is a central peripheral test which
measures how eyes are aligned when the peripheral vision and the
central vision of each eye are aligned with each other. The third
test is an EXO peripheral test which measures how the eyes are
aligned when the peripheral vision and the central vision of each
eye are uncoupled from each other independently. The fourth test
measures torsional rotation of each eye under monocular and
binocular conditions. The fifth test measures slow drifts as the
patient views targets.
[0072] The computer 140 synchronously controls the patient stereo
LCD monitor 174 and the LCD shutters 134L and 134R using
conventional stereoscopic techniques which are well known.
Particularly, the computer 140 uses separate stereo displays for
the left and right eyes, each including a distinct image. These
displays are alternated in synchronization with the shutters 134L
and 134R at 120 frames per second. As is known, the LCD shutters
134L and 134R are controlled to be "opened" in a clear state or
"closed" in an opaque state. When the left LCD shutter 134L is
open, the image intended for the left eye is displayed on the
monitor 174. When the right LCD shutter 134R is open, the image
intended for the right eye is displayed on the monitor 174.
[0073] Referring to FIG. 7, a flow diagram illustrates operation of
the system 102 for measuring fixation disparity using one the five
tests discussed above. The system starts at a node 300 and then
implements an initialization routine at a block 302. This sets up
communication with the microcontroller 172 and initiates operation
of the LEDs 136 and the cameras 180L and 180R. Prior to performing
the test it is necessary for the patient's eyes to be properly
positioned vertically relative to the shutters 134L and 134R and
for the cameras 180L and 180R to be aligned with the lines of sight
204L and 204R, respectively. The operator monitor 150 will display
the camera images of the patients eyes advantageously relative to a
reference grid which can be used by the operator to provide the
proper alignment. This is done beginning at a decision block 304
which determines if the eyes are vertically centered. If not, then
the chin stepper motor 186 is manually controlled by the operator
using any desired input commands at a block 306 to move the chin
support 114, see FIG. 2, up or down. The operator will use the
operator LCD monitor 150 to view the position of the eyes to
determine if they are vertically centered. Once the eyes are
vertically centered, then a decision block 308 determines if eye
spacing is correct. Eye spacing is correct if the spacing between
the lenses 198L and 198R, and thus also camera 180L and 180R,
corresponds to the patient's pupillary distance. If not, then the
left and right steppers 182L and 182R are manually controlled at a
block 310 until the eye spacing is correct. Again, the operator can
use the display on the monitor 150 to determine the correct
position.
[0074] Once the eye spacing is correct, then the operator can
implement any one or more of the central monocular tests at a block
312, the central peripheral test at a block 314, the EXO peripheral
test at a block 316, the torsional rotation test at a block 318,
and the slow drift test at a block 320. Once the operator has
completed any or all of the tests, then the operation ends at a
node 322.
[0075] With the central monocular test, a small central target is
viewed and alternated between the left and right eyes in a dark
environment while peripheral vision is kept isolated. A small
central target is seen only by the left eye for less than one
second, then alternated to the right eye for the same amount of
time. The movement of each eye is tracked for a period of time as
the small central target is alternated between the right and left
eyes. The computer 140 relocates the target for both right and left
eyes to match the position of each eye in order to measure fixation
disparity. Initially, the patient will notice that the target
appears to jump from side to side and possibly up and down. Once
the tracking system monitors the movement of each eye and relocates
the target, then the patient will notice very little movement
between the target seen with the right eye and then seen with the
left eye. In other words, the two targets appear to be physically
coincident.
[0076] Referring to FIG. 8, a flow diagram illustrates a software
routine implemented by the computer 140 for the central monocular
test 312. This test begins at a block 400 which sets initial target
spacing. The initial center target spacing represents ideal spacing
between left and right image targets according to the patient's
pupillary distance when viewing an object to focus at infinity. For
this test, the LCD monitor 174 displays a black background. The
central target comprises a small white circle with a small center
dot. As will be appreciated, other target shapes could be used.
FIG. 9A illustrates the display image for the left eye, while FIG.
9B illustrates the display image for the right eye. Thus, FIG. 9A
illustrates the left eye central target 402L and FIG. 9B
illustrates the right eye central target 402R. As is apparent, the
locations of the targets 402L and 402R on the display 174 are
physically spaced apart based on the initial center target spacing.
Once the initial center target spacing is set, then a block 404
builds left and right stereo displays. This comprises building the
static displays as shown in FIGS. 9A and 9B respectively, with the
positions of the targets 402L and 402R being adjustable under
control of the program.
[0077] The program then "flashes" the left target 402L at a block
406. This comprises showing the patient the left eye image shown in
FIG. 9A. The program waits a select flash time at a block 408. This
flash time may be on the order of 0.5 second to 1 second, as
necessary or desired. As described above, the stereo control is
separately determining which of the left or right eye is viewing
this image using a rate on the order of 120 frames per second. At
the end of the flash time, then the program measures the left and
right eye positions at a block 410. This is done using conventional
eye tracking software receiving images from the cameras 180L and
180R. The software determines the pupil position of the patient's
left and right eyes. The program then flashes the right target
402R, shown at FIG. 9B, at a block 412. This comprises showing the
patient the right eye image shown in FIG. 9B. The program waits the
select flash time at a block 414, and measures left and right eye
positions at a block 416 at the conclusion of the wait time. The
program then determines eye movement at a block 418. This compares
the eye positions measured at the blocks 410 and 416. This movement
can be side to side and/or up and down. This initially looks at the
relative movement of the left and right eyes in order to cancel any
head movement and then determines net movement. Based on this, the
computer determines a correction factor based on net eye movement
which seeks to converge the position of the central targets 402L
and 402R so that the patient perceives the left and right targets
402L and 402R to be physically coincident.
[0078] Particularly, a decision block 420 determines if the
determined eye movement is greater than a select amount X. The
amount X is selected to represent no eye movement or that there is
substantially no eye movement corresponding to the perceived images
being coincident with one another. If the eye movement is greater
than X, then the correction factor is determined at a block 422 and
new target spacing is set at a block 424 using the correction
factor. The program then moves the targets 402L and 402R to the
corrected positions and builds the resulting displays at the block
404. The process discussed above continues and is repeated until
eye movement is less than X, at which time the total measured
displacement, corresponding to the amount the central targets are
moved on the monitor 174 and representing fixation disparity, is
recorded at a block 426 and the routine ends.
[0079] As is apparent, the program may determine that the central
target has been moved to the left or to the right or up or down, as
necessary to make it appear that the targets 402L and 402R are in
the same position. As discussed above, FIGS. 9A and 9B illustrate
the initial target spacing. FIGS. 10A and 10B illustrate an example
of final target spacing at the conclusion of the test. In this
example the left eye central target 402L has been moved up and to
the right, while the right eye central target 402R has been moved
to the left and down. FIG. 11 successively illustrates the
patient's perspective of the targets 402L and 402R from the initial
spacing shown as no correction to the final position where the
targets are substantially coincident with one another. In this
example there are three steps of correction used to move from the
initial position to the final correction position. The displacement
recorded at the block 426 represents the amount of movement from
the no correction position to the final correction position, which
can be expressed, for example, in screen pixels or prism diopters,
or the like.
[0080] The procedure described above which iteratively repositions
a central target to measure fixation disparity is also used for the
central peripheral test and the EXO peripheral tests. These tests
otherwise differ in the use of additional peripheral targets and
provide comparative results which illustrate how the peripheral
targets affect the measured fixation disparity.
[0081] FIG. 12 illustrates a flow diagram for the central
peripheral test 314. This flow chart is generally similar to that
for the central monocular test 312, see FIG. 8, and the blocks are
similarly numbered except being in the 400's rather than the 300's.
This routine differs principally in the left and right stereo
displays built at a block 504 and adjusted at a block 524. With the
central monocular test, the patient's peripheral vision was not
stimulated. With the central peripheral test, the small central
target is viewed only one eye at a time and alternated between the
left and right eyes, while peripheral vision is viewing a constant
peripheral target that is geometrically aligned with the central
target and thus their central vision. This is illustrated in a
basic form in FIGS. 13A and 13B, which shows the left eye display
and the right eye display, respectively, corresponding to settings
for initial center target spacing, as noted above. For this test, a
black background is again used on the display monitor 174. The
peripheral target comprises a white circle 502PL and 502PR. The
central image target comprises a black dot 502CL and 502CR
selectively centered in the corresponding white circles. For this
test, the black dot center target is located in the center of the
peripheral target which moves with the center target. The left eye
display is shown in FIG. 13A in which both peripheral targets 502PL
and 502PR are displayed and the left center target 502CL comprises
a dot in the center of the left peripheral target 502PL. There is
no central target in the right peripheral target 502PR. FIG. 13B
illustrates the display for the right eye in which the left eye
peripheral target 502PL includes no central target, while the right
eye peripheral target 502PR includes the central target 502CR.
[0082] As with the central monocular test, the left eye image, as
shown in FIG. 13A, is flashed for the wait time and then
alternately the right eye image, as shown in FIG. 13B, is flashed
for the wait time with eye positions being measured and
subsequently eye movement determined at the block 518, as
above.
[0083] Thus, as described, a small central target 502CL or 502CR is
viewed only one eye at a time and alternated between the left and
right eyes while the peripheral vision is viewing the constant
targets 502PL and 502PR that are geometrically aligned with the
central targets 502CL and 502CR. The left central target 502CL is
seen for less than one second, then alternated to the right central
target 502CR for the same amount of time. The movement of each eye
is tracked for a period of time as the target is alternated. The
computer 140 relocates the target for both the eyes to match the
position of each eye, as discussed above. This is illustrated in
FIGS. 14A and 14B, which show the final position. FIG. 15 shows the
patient's perception at each step of correction from no correction,
based on the image in FIGS. 13A and 13B, to the final correction
based on the images shown in FIGS. 14A and 14B. The displacement of
the center targets 502CL and 502CR from the position shown in FIGS.
13A and 13B to that shown in FIGS. 14A and 14B, respectively, is
recorded at the block 526.
[0084] FIG. 16 illustrates a flow diagram for the EXO peripheral
test 316. During the EXO peripheral test, peripheral vision is
isolated from central vision and adjusted independently until
central vision and peripheral vision align with each other. With
this test, a small central target is viewed only one eye at a time
and alternated between the right and left eyes while peripheral
vision is viewing constant peripheral targets that are not
geometrically aligned with central vision. These peripheral targets
may be stationary, but often are set into motion in order to keep
peripheral vision stimulated and fused.
[0085] The flow diagram of FIG. 16 is generally similar to the flow
charts of FIGS. 6 and 11, and the blocks are similarly numbered
except being in the 600s. This routine differs principally in the
left and right stereo displays built at a block 604 and adjusted at
a block 624. This is generally illustrated in a basic form in FIGS.
17A and 17B, which illustrate the left eye image displays and right
eye image displays, respectively, which are built at the block 604.
For this test, a black background is again used on the display
monitor 174. The peripheral target comprises a white circle 602PL
and 602PR. The central image target comprises a black dot 602CL and
602CR selectively decentered in the corresponding white circles.
The two peripheral targets 602PL and 602PR are constant targets but
are not geometrically aligned with the central targets 602CL and
602CR. As with the tests above, the central targets 602CL and 602CR
are alternately flashed and eye movements measured as discussed
between the blocks 606 and 616 to determine movement at a block 618
and, if there is eye movement greater than the amount X at block
620, to determine a correction factor at block 622 and set new
center target spacing at a block 624. This proceeds until the
center target 602CL and 602CR appear generally coincident with one
another using the final correction, as shown in FIG. 19, based on
the positions of the display shown in FIGS. 18A and 18B. The
displacement of the center targets 602CL and 602CR from the
position shown in FIGS. 17A and 17B to that shown in FIGS. 18A and
18B, respectively, is recorded at the block 626.
[0086] Thus, with each of the central monocular test, central
peripheral test, and EXO peripheral test, a target is presented to
the left eye for less than a second, then simultaneously as the
target is turned off to the left eye it is turned on to the right
eye. This is alternated back and forth as the camera system tracks
the movement of the eyes. If the left eye is viewing the target,
the right eye goes to a position of rest. This happens for multiple
reasons. Initially, this is because there is no target for the
right eye to look at, and secondly because the left eye is looking
at the target and the patient can't discern which eye they are
looking with during the test. The patient often thinks that they
are looking at the target with both eyes instead of just one eye.
Also, there is no stimulus for the two eyes to work together due to
the shutter glass technology.
[0087] While the patient is viewing the target with the left eye,
the camera system takes a snapshot of the position of the right
eye. Then when the target is alternated to the right eye, the right
eye will move in order to pick up fixation to the central target.
Then another picture of the right eye is taken. The computer 140
calculates where the eye was before the target was presented then
where the eye moved to after the target is visible. After
alternating between the left and right eyes and taking pictures of
both eyes before it sees the target and after it is fixated on the
target, the system calculates the movement of each eye and
relocates the targets in order to minimize the movement of the eyes
as the eye goes from no target to seeing a target. The difference
in the peripheral tests is how the peripheral target is presented
in relation to the central target. During the central monocular
test there is no stimulus to the peripheral vision, since the
peripheral vision is looking at a black screen. In the central
peripheral test and EXO peripheral test, there is constant stimulus
to the peripheral vision of both eyes. The right eye and left eye
see separate, constant, and similar targets and the brain puts
these independent pictures from each eye together to make a
three-dimensional stereoscopic picture. Altering the location of
the peripheral images creates more or less three-dimensional depth.
Thus, the system allows the patient to have peripheral vision fused
together creating a three-dimensional image, while the central
vision is isolated from having binocular vision, as only one eye
can see one target at a time. This sets up a dynamic way to measure
the relationship how our brain fuses a peripheral target in
relationship to how it fuses the central target that is being
viewed.
[0088] As described above, a basic form of the methodology uses a
white circle as the peripheral target. Alternative peripheral
targets may be used for the central peripheral test and the EXO
peripheral test. FIG. 20 illustrates an alternative for the central
peripheral test in which a plurality of planets and stars are
illustrated as peripheral targets. In this illustration, there are
three planets and three stars. With respect to the stereoscopic
implementation of the planets, one is shown in solid line, which is
for the left eye image, while one is shown in dashed line, which is
for the right eye image. Similarly, each star includes two images,
one for the left eye and one for the right eye. These stars and
planets can be presented in 3-D with shadowing and different colors
and the like. Similarly, the planets and stars can be moving as
shown in FIG. 21, in which the planets rotate in an orbit around
the central targets. Moreover, the planets may spin while going
through the orbit. The stars may similarly rotate and spin. As is
apparent, additional planets and/or stars could be used, with some
planets orbiting in one direction and others in the opposition
direction, as with the stars. The rotation of any of these is at
the same angular rate, with some in one direction and others in the
opposition direction. The planets and the movement are continuous
and only the central target flashes. With any option, the
peripheral targets are always shown to the left eye and the right
eye using the stereoscopic control discussed above, while the
central target is alternated or flashed, so that only the left or
the right central target is shown at any given time, as discussed
above. While the peripheral vision wants to view the peripheral
targets, the objective of the test is for the patient to ignore the
peripheral targets.
[0089] FIG. 22 illustrates an alternative for the EXO peripheral
test in which the peripheral target is a single planet, shown
stereoscopically one for the left eye image and one for the right
eye image displaced from the central targets and not aligned. In
this case, the peripheral targets can be moved left and right,
opposite one another, independently of movement of the central
target.
[0090] With each of the central monocular test, central peripheral
test, and EXO peripheral test, the amount of displacement may vary.
The recorded displacement data can be used as warranted for
preparing prescription lenses to accommodate for the fixation
disparity which appropriately adjusts prism or the like for the
patient. The target of the test is to determine how the peripheral
images impact the central vision perception of the target.
[0091] As will be apparent, there are numerous options for how the
peripheral targets are displayed, it being understood that for the
peripheral tests both the left eye and right eye will always see
the left peripheral targets and right peripheral targets,
respectively, while the central targets will flash. The invention
is not intended to be limited to any form of the peripheral targets
or central targets.
[0092] With respect to the torsional rotation test, described at
the block 318 of FIG. 7, there are six independent muscles that
control movement of each eye. Depending on the neurological
intervention of each of these muscles, the location of the
patient's head in relation to where the patient is looking and the
position of the target, above or below, a combination of these
muscles are used to move the eyes up, down, left or right. Cranial
nerves III and IV and VI work together in order to reposition the
eye to different locations. When this happens there is often cyclic
rotation of the eye. This rotation can be measured and captured by
the computer 140. This is done by noting the rotation of the eyes
when the system changes the location of where the eyes are looking.
The rotation can be measured in the same fashion as the eye
movement is captured. A snapshot, or streaming video of the
location of the eye prior to the central target and again after the
target is turned off, using the cameras 180L and 180R.
[0093] The slow drifts test initiated at the block 320 can also use
the camera images. When fixating on a target with our central
vision, there is a natural oscillation or very fine eye movement
that constantly exists in order to help keep our eyes fixated on
the target being viewed. As one stares at a target, the eyes will
start to drift away from what is being viewed. These slow drifts
can be measured under monocular and binocular conditions. The
computer compares images at set intervals using setup parameters
with these intervals.
[0094] Thus, using the system for measuring visual fixation
disparity and the corresponding methodology, the system presents
stereoscopic visual content to the patient using central targets
and peripheral targets while measuring eye movement to determine
fixation disparity.
[0095] It will be appreciated by those skilled in the art that
there are many possible modifications to be made to the specific
forms of the features and components of the disclosed embodiments
while keeping within the spirit of the concepts disclosed herein.
Accordingly, no limitations to the specific forms of the
embodiments disclosed herein should be read into the claims unless
expressly recited in the claims. Although a few embodiments have
been described in detail above, other modifications are possible.
For example, the logic flows depicted in the figures do not require
the particular order shown, or sequential order, to achieve
desirable results. Other steps may be provided, or steps may be
eliminated, from the described flows, and other components may be
added to, or removed from, the described systems. Other embodiments
may be within the scope of the following claims.
* * * * *