Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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PROCESS AND DEVICE FOR APPORTIONING THERAPEUTIC VISION
STIMULI
Technical Field
The present invention relates to focused vision therapy and, in particular, to
selectively apportioning light stimulation to different areas of a patient's
visual field.
Back2round
Stimulating the vision system of human subjects with vision impairment may
improve their visual performance. For example, as documented in US Patent No
lo 6,464,356, and US Published Patent Application No. 2005/0213033, presenting
visual
stimuli to areas of a human's visual system may allow improvement in the
user's vision.
NovaVision, of Boca Raton, Fl, produces VRT TM (Visual Restoration Therapy)
devices
for effecting optical stimulation of defined locations of a patient's retina.
During a course
of VRT, a finite number of stimulation events are available. Therefore, these
stimulation
events should be judiciously directed to the particular visual field regions
for which
treatment is desired. .
VRT may be used to treat neurological deficits of the visual system of a
patient.
Such deficits may result from retinal damage, damage to the optic nerve,
damage to the
visual cortex, such as may occur due to stroke or traumatic brain injury. For
example,
age related macular degeneration (AMD) may be treated with VRT.
Summary of the Invention
In accordance with an illustrative embodiment of the invention, there is a
method
for treating the visual system of a human. The method comprises situating the
human in
proximity to a computer-actuated light emitting array that has a set of
individually
actuable elements. A campimetric representation of the visual field is used to
select a
stimulus distribution that is biased toward the central visual field. An
actuable element
subset is selected from the set of individually actuable elements based on the
stimulus
distribution. The subset of elements is actuated to emit a light stimulus that
is directed to
a specified region of the human's visual field.
Various related embodiments are provided including optional or additional
features. For example, a fixation stimulus may be presented to the human. The
steps of
selecting and actuating the light stimulus may be repeated for a given number
of cycles.
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A further step of recording the human's response to the stimuli may be
included. The
steps of selecting the stimulus, actuating the stimulus, and recording the
human's response
may be repeated for a given number of cycles. A record of the human's response
to the
stimuli may be used to update the distribution. For example, a change in the
response
with time for a given visual field location may be used to update the
distribution. The
distribution may be automatically updated. These subset of actuable elements
may be a
single actuable element. The actuable elements may be pixels of a computer
display.
The retinal area targeted by the subset of the elements may be in increasing
relationship
with corresponding distance from the center of the human's visual field. For
example,
larger subsets may be selected to target peripheral visual field regions and
smaller subsets
to target central visual field regions.
In another embodiment of the invention, there is a method for treating the
visual
system of the human comprising using a campimetric representation of the
visual field to
define at least a primary zone, a secondary zone, and a remainder zone. The
remainder
zone comprises that portion of the visual field that is outside of the other
defined zones.
A human is situated in proximity to a computer-actuated light emitting array
that has a set
of actuable elements. An actuable element subset is selected from the set of
individually
actuable elements and the subset is actuated to emit light stimulus directed
to a specified
region of the human's visual field. The selection of the actuable elements
includes
administering an apportioning bias in favor of the primary zone.
Various related embodiments are provided including optional or additional
features. The steps of selecting an actuable element subset and actuating the
elements to
emit light stimulus may be repeated over a course of a therapeutic session so
as to present
a greater number of stimuli to the primary zone than to the secondary zone or
to the
remainder zone. The steps of selecting an actuable element subset and
actuating the
elements to emit light stimulus may be repeated over a course of a therapeutic
session so
as to present a greater number of stimuli to the primary zone than to the
secondary zone
or to the remainder zone, and a greater number of stimuli to the secondary
zone than to
the remainder zone. The number of the stimuli of presented to the remainder
zone may
be non-zero. A further step of recording the human is response to the stimuli
may be
included. A cycle of selecting a stimulus actuating the stimulus and recording
the
human's response may be repeated for a given number of cycles. The record of
the
human's response to the stimuli may be used to redefined the primary zone or
the
secondary zone. A change in the response with time for a given visual field
location may
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be used to redefine the zone. The redefinition may be done automatically.
These subset
of actuable elements may be a single actuable element. The retinal area
targeted by the
subset of elements may increase with corresponding distance from the center of
the
human's visual field. For example, larger subsets of elements may be selected
to target
peripheral visual field regions and smaller subsets selected to target central
visual field
regions.
In accordance with yet another embodiment of the invention, there is a method
for
treating the visual system of a human. The method includes using a campimetric
representation of the visual field to define a transition zone that is
bordered by a blind
zone and an intact zone. A human is situated in proximity to a computer-
actuated light
emitting array having a set of actuable elements. A subset of actuable
elements is
selected and actuated to a emit light stimulus directed to the transition zone
of the
human's visual field. The selecting and actuating steps are repeated to
effectuate a
course of therapy. The selection includes a bias for central visual field
regions.
Various related embodiments are provided including optional or additional
features. The method may include recording the human's response to the
stimuli. The
record of the human's response to the stimuli may be used to update the
definition of the
transition zone. Updating the transition zone may include using a change in
the response
with time for a given visual field location. The zone may be redefined
automatically.
In a further embodiment of the inventions, there is a system for treating the
visual
system of a patient. The system includes a display that has an array of
individually
actuable light emitting elements to present stimuli to a human during a course
of therapy.
The system also includes an apportioner that is adapted to accept a
campimetric
representation of the visual field and apportion a sequence of stimuli to
specified regions
of the visual field. The system also includes an actuator for actuating
display elements
according to the apportionment of the apportioner. The apportioner apportions
a greater
share of stimuli to those the visual field regions nearer the center of the
visual field.
Various related embodiments are provided including optional or additional
features. The actuator may present a fixation stimulus to the human. The
system may
include software and/or hardware for recording the human's response to the
stimuli, for
using the record of the human's response to the stimuli to allocate future
stimuli and/or
for using a change in the response with time for a given visual field location
to allocate
future stimuli. The system may include software and/or hardware for increasing
the
targeted retinal area of the presented stimulus increases with corresponding
distance from
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the center of the human's visual field. The retinal area may be targeted by
the subset of
elements in increasing relationship with corresponding distance from the
center of the
human's visual field by selecting larger stimuli to target peripheral visual
field regions
and smaller subsets to target central visual field regions.
In a further embodiment of the invention, there is a system for treating the
visual
system of a patient. The system includes a display having an array of
individually
actuable light emitting elements to present stimuli to a human during a course
of therapy
and an apportioner that is adapted to accept a campimetric representation of
the visual
field and apportion a sequence of stimuli to specified regions with the visual
field. The
system also includes an actuator for actuating display elements according to
the
apportionment of the apportioner. The apportioner apportions by using a
campimetric
representation of the visual field to define at least a primary zone, a
secondary zone, and a
remainder zone, the remainder zone comprising that portion of the visual field
that is
outside of the other defined zones.
Various related embodiments are provided including optional or additional
features. The system may include software and/or hardware for presenting a
greater
number of stimuli to the primary zone than to the secondary zone or to the
remainder
zone. The system may include software and/or hardware for presenting, over the
course
of therapy, a greater number of stimuli to the primary zone than to the
secondary zone or
to the remainder zone, and a greater number of stimuli to the secondary zone
than to the
remainder zone. The number of stimuli presented to the remainder zone may be
non-
zero. The system may include software and/or hardware for recording the
human's
response to the stimuli, for using the record of the human's response to the
stimuli to
allocate future stimuli and/or for using a change in the response with time
for a given
visual field location to allocate future stimuli. The system may include
software and/or
hardware for increasing the targeted retinal area of the presented stimulus
increases with
corresponding distance from the center of the human's visual field. The
retinal area may
be targeted by the subset of elements in increasing relationship with
corresponding
distance. The system may include software and/or hardware for using the record
of the
human's response to the stimuli to redefine one of the primary zone and the
secondary
zone. The system may usea change in the response with time for a given visual
field
location to redefine one of the primary zone and the secondary zone. The zone
may be
automatically redefined.
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In a further embodiment of the invention, there is a system for treating the
visual
system of a patient. The system includes a display having an array of
individually
actuable light emitting elements to present stimuli to a human during a course
of therapy
and an apportioner that is adapted to accept a campimetric representation of
the visual
field and apportion a sequence of stimuli to specified regions with the visual
field. The
system also includes an actuator for actuating display elements according to
the
apportionment of the apportioner. The apportioner apportions by using a
campimetric
representation of the visual field to define at a transition zone bordered by
a blind zone
and an intact zone and apportion stimuli to the transition zone with a bias
toward the
central visual field.
Various related embodiments are provided including optional or additional
features.
The system may include software and/or hardware for recording the human's
response to
the stimuli, for using the record of the human's response to the stimuli to
update the
transition zone, for updating the transition zone using a change in the
response with time
for a given visual field location, and for automatically redefining the
transition zone.
Brief Description of the Drawin2s
The foregoing features of the invention will be more readily understood by
reference to the following detailed description, taken with reference to the
accompanying
drawings, in which:
Fig. 1 shows a flow chart of a method of visual restoration therapy in
accordance
with an embodiment of the invention;
Fig. 2 shows an example of a training area having three (3) sub-areas;
Fig. 3 shows a visual field map with a blind zone, intact zone and transition
zones;
Fig. 4 shows a visual field map with a defined border zone and central visual
field;
Fig. 5 shows a visual field map with multiple defined apportionment zones;
Fig. 6 shows a visual field map before and after therapy;
Fig. 7 shows how a particular visual field location may improve with therapy.
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Detailed Description of Specific Embodiments
Definitions. As used in this description and the accompanying claims, the
following terms shall have the meanings indicated, unless the context
otherwise requires:
"VRT" shall mean visual restoration therapy, a therapeutic process for
selectively targeting and stimulating specific visual field regions;
An "light emitting array having a set of individually actuable elements"
shall mean any device capable of transmitting an illuminating pattern to the
retina of a
human including a cathode ray tube (CRT), liquid crystal display (LCD),
organic light
emitting diodes (OLED), or other such device which may be placed at various
distances
from a patient's eyes, and includes head mounted displays and image projection
methods
including the use of digital light processing (DLPTM)
In the context of visual restoration therapy, a "campimetric representation"
shall mean any data set that associates a set of visual field positions with
at least one
corresponding patient performance data set. The patient performance data may
include
patient response times, or threshold intensity required to observe a stimulus;
A "course of VRT" shall mean any temporally continuous or
discontinuous VRT session, which may span minutes, hours, days, weeks,
months, or years;
An "apportioner" shall mean any device including hardware, software or
both capable of apportioning a finite number of individual light stimuli
events between
specified visual field zones according to a particular bias. For example, the
apportioner
may be embodied in a computer with software for administering VRT. In the
context of an apportioner, a "bias" shall mean a skewing of stimulus
apportioning so as to
stimulate a particular zone to a greater degree than one or more other zones.
An "actuator" shall mean any device capable of switching array elements
so as to illuminate the retina of a patient with a given pattern and
distribution of stimuli
Aspects of the present invention may solve the problems outlined above by
apportioning or rationing stimuli over a course of VRT so as to optimize
stimulation to
obtain more significant clinical outcomes when using limited amounts of light
stimuli.
For a given length of therapy (e.g., a single session, or a course of therapy
over weeks or
months), a patient will receive a finite number of stimuli. For example, a
patient may
receive 500-600 stimuli in a 20 to 30 minute VRT session. A therapist may
desire to
stimulate multiple visual field zones (e.g., both functionally important
central areas and
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ARVs). However, a tradeoff must be made between the number of stimuli directed
at a
given zone and areal coverage. Illustrative embodiments of the present
invention may
solve some of these or other problems by dividing a therapy area into regions
and
applying different stimuli densities to each region. Unless otherwise
indicated, the
operations of the VRT systems described below may be fully automatic in the
sense that
the therapist need not intervene during a therapy session or even a multi-
session course of
therapy.
Fig. 1 shows a flow chart in accordance with an embodiment of the invention.
The flow chart represents a method that may be embodied in a VRT apparatus or
software module for use with a VRT apparatus. As is known in the art, a
patient is
situated in front of a display and instructed to fixate upon a fixation point
or stimulus.
The display may be a computer driven CRT, LCD, OLED, DLP, plasma display, or
other
such display including a head mounted display (e.g., goggles or helmet). The
display has
associated hardware for actuating subsets of individual elements of the
display from a set
(e.g. pixels or subsets of pixels) in order to target a specific area of the
patient's retina
and neuronal components of their visual field with a patterned illumination.
The patterned
illumination may be a single pixel, a contiguous subset of pixels that project
a particular
shape, or even a discontiguous subset of pixels. Targeting of the illumination
pattern
upon the retina may be accomplished by applying a specified offset from a
point upon
which the patient is instructed to fixate (i.e. a fixation point).
A campimetric representation of the patient's visual field (a "visual field
map") is
obtained (step 110). The representation may be manifested as a multi-
dimensional data
set or visual field map, either as an array in computer memory, or expressed
graphically.
The campimetric representation may be the result of a previous VRT session or
other
campimetric activity. For example, the campimetric representation may contain,
as a
function of position relative to the a fixation point, or in an array
corresponding to pixels
on a VRT display, response times, fraction of correct responses, or other data
related to
the sensitivity of the patient's visual field neurons to light stimuli.
Alternately, rather
than starting with the map, the map can be generated through subsequent steps
in the
process, such a those listed below.
The campimetric representation is then used to assign the potential for a
given
neuron or visual field area to respond to VRT (step 120). For example,
depending on the
type of therapy chosen by the therapist, regions of the visual field that are
partially
responding, or are in a transition zone between a blind zone and an intact
(i.e., seeing)
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zone may be indicative of a high recovery potential. Scores may be assigned
based on
potential. In an another example, a visual field location corresponding to a
pixel element
of a VRT may be assigned a low score if bounded on all sides by nonresponsive
locations
(i.e., blind regions), or bounded on all sides by intact regions, whereas
locations bounded
by both blind and intact locations, or one or more partially responding
locations, may be
awarded a higher scores. Trending data, i.e. improvements or decreases in
patient
responses in a given visual field areas may also be used to assign priorities;
e.g., stimuli
may be better invested in those areas showing an improvement with time. The
result of
step 120 may be used as a priority map, which may be used to distribute (i.e.,
apportion)
stimuli among multiple locations.
In a specific example of a scoring system, points are awarded to each element
in a
two dimensional array of VRT pixel locations as follows:
i) locations adjacent to 8 blind locations (locations include diagonal
locations) - 0
points;
ii) locations adjacent to 8 intact locations - 0 points;
iii) locations adjacent to one or more partially responding locations - 1
point for
each partially responding location;
iv) locations adjacent to both blind and intact locations - 5 points
Optionally, additional factors may be used to assign priorities (step 130).
Examples of additional factors include therapist intervention, or application
of additional
biases, which may be arrived at by using physiological or statistical factors.
In one
embodiment, a physiological bias is included that favors more central visual
field regions
over more peripheral regions so as to create a stimulus distribution that
effects
presentation of a larger fraction of the administered stimuli to more central
regions.
Thus, result may be desirable because more central regions of the visual field
(e.g., the
center 3-5 ) have more neuronal synapses and are thus critical in certain key
activities
such as reading. The stimuli distribution can be tuned to match approximately
the
number of neuronal synapses at a given location (i.e. the cortical
magnification factor) by
using population-derived visual field structures, or maps of the individual
patient's visual
field.
Stimuli are apportioned to the patient based on the assigned priorities by
actuating
the individual actuable light-emitting elements of a display device to target
a specified
region of the patient's visual field. Various techniques are available to
apportion the
stimuli, including:
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i) randomly assigning locations, and multiplying by a weighting factors based
on
a corresponding scores from those location obtained from the priority map; and
ii) populating a location table with a list of locations, the locations having
a
frequency that is proportional to priority scores. The sequence of location
presentations
may then be randomized. Additionally, the list may be further sorted to
temporal
clustering of stimuli presentations in a given area or zone.
After presenting a given stimuli, a patient response may be recorded; e.g.,
the by
detection of a button actuation by the patient. Response times may also be
recorded.
Patient responses may be used to update the visual field map "in real time,"
i.e., prior to
completion of a therapy session or course of therapy. In other words, the loop
is closed
by returning to step 110 and repeating the loop for the duration of therapy
(step 160). As
discussed above, derivative aspects of the patient response, including
temporal
improvements of the patient response accuracy, response time, or threshold
intensity
required for a patient to see a stimulus may be utilized in setting priorities
and assigning
the apportioning distribution. Alternately, the loop may be closed by
returning to step
140.
In accordance with another embodiment, the effectiveness of stimulus
allocation
is improved by varying the size of a stimulus according to the selected visual
field
location targeted by the stimulus. Because visual field resolution decreases
with distance
from the center of the visual field in a known way, stimulation of various
neurons can be
accomplished with different stimulus sizes (e.g., by altering the number of
adjacent
elements actuated). This approach may result in improved economies of
stimulation
allocation. For example, a computerized VRT apparatus may use an algorithm
that
randomly distributes stimuli, but avoids repetitive stimulation in the same
location; using
larger stimuli in peripheral regions of the visual field will result in a bias
in favor of the
central visual field. The larger stimuli are sized so as to illuminate a
larger area of the
patient's retina.
Fig. 2 shows a visual field map of a patient. Because the map would be
generated
using a VRT device, it is pixelated according to an array of actuable light
emitting
elements associated with a VRT apparatus. A fixation point 210 is used as a
reference.
The map has been divided into four zones: a primary zone 230, a secondary zone
220, a
tertiary zone 240, and remainder zone 250 (the area not defined as one of the
other
zones). Although shown as continuous zones, the zones may also be
discontinuous. The
zones may be defined automatically or manually according to campimetric data.
In an
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embodiment of the invention, a given, finite number of stimuli are apportioned
among
two or more zones. For example, 80% of the stimuli may be apportioned to the
primary
zone 230 and 20% to the secondary zone. Alternately, some fraction may be
reserved for
the tertiary zone, higher order zones, the remainder zone, or combinations
thereof
In a specific embodiment, the transition zone is defined as the primary zone
and
receives the majority of the stimuli, e.g., 70%. The remaining stimuli are
presented to a
border region secondary zone. The transition zone may be either continuous or
discontinuous. The border region may be sized to extend beyond the transition
zone into
both blind and intact zones by a certain amount. For example, approximately
two visual
field cells on either side of the transition zone may be targeted. The patient
response
record may be used, periodically or continuously, to update the transition
zone definition.
A central visual field bias may also be applied to the transition zone.
In a related embodiment, vision is more intensely stimulated in a given zone,
yet
patient response is tracked by stimulating outside the given zone with fewer
stimuli, and
optionally, at a lower frequency (i.e., stimuli per unit time) in order to
track patient
response across a larger visual field region or the entire visual field. In
this way, the
various cells in the visual field are reconnoitered for potential recruitment
into the set of
locations receiving the more intense or frequent therapy. For example, in this
way, a cell
may be discovered to be exhibiting a recovery trend and the therapy regimen is
adjusted
accordingly (either automatically, or manually)
Figs. 3-7 show a VRT process according to an embodiment of the present
invention. Fig 3 shows, in map format, a campimetric representation of a
patient's visual
field obtained using a VRT apparatus. A transition zone is defined by non-
contiguous
high-potential regions 330, portions of which lie within an intact zone 320, a
blind zone
310, or adjacent both the intact and blind zones. Fig. 4 shows a border region
410 and a
central field region 420 that may be used in assigning stimulus apportioning
priorities.
Accordingly, as shown in Fig. 5, multiple zones may be created. Thus, a
primary zone
510 is apportioned 70% of the stimuli, a secondary zone 520 is apportioned 20%
of the
stimuli, and a noncontiguous tertiary zone 530 is apportioned 10% of the
stimuli. Fig. 6
shows how, after a course of VRT treatment with the so-apportioned stimuli,
the zones
may be redefined to reflect changes in the patient's responsiveness
(improvement or
deterioration). Fig. 7 shows how a particular map element corresponding to a
particular
neuron may indicate improvement in responsiveness of the particular neuron
over a
course of stimulative therapy.
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In various embodiments, zones may be defined and redefined automatically.
However, tools may be provided to a therapist to define zones manually. For
example,
zones may be drawn on a computer screen so as to overlay a visual
representation of the
visual field (e.g., a campimetric map). For example, circles or ovals may be
drawn to
demark a zone for preferential stimulus apportionment.
In alternative embodiments, the disclosed methods for stimulative therapy may
be
implemented as a computer program product for use with a computer system. Such
implementations may include a series of computer instructions fixed either on
a tangible
medium, such as a computer readable medium (e.g., a diskette, CD-ROM, ROM, or
fixed
disk) or transmittable to a computer system, via a modem or other interface
device, such
as a communications adapter connected to a network over a medium. The medium
may
be either a tangible medium (e.g., optical or analog communications lines) or
a medium
implemented with wireless techniques (e.g., microwave, infrared or other
transmission
techniques). The series of computer instructions embodies all or part of the
functionality
previously described herein with respect to the system. Those skilled in the
art should
appreciate that such computer instructions can be written in a number of
programming
languages for use with many computer architectures or operating systems.
Furthermore, such instructions may be stored in any memory device, such as
semiconductor, magnetic, optical or other memory devices, and may be
transmitted using
any communications technology, such as optical, infrared, microwave, or other
transmission technologies. It is expected that such a computer program product
may be
distributed as a removable medium with accompanying printed or electronic
documentation (e.g., shrink wrapped software), preloaded with a computer
system (e.g.,
on system ROM or fixed disk), or distributed from a server or electronic
bulletin board
over the network (e.g., the Internet or World Wide Web). Of course, some
embodiments
of the invention may be implemented as a combination of both software (e.g., a
computer
program product) and hardware. Still other embodiments of the invention are
implemented as entirely hardware, or entirely software (e.g., a computer
program
product).
The described embodiments of the invention are intended to be merely exemplary
and numerous variations and modifications will be apparent to those skilled in
the art. All
such variations and modifications are intended to be within the scope of the
present
invention as defined in the appended claims.
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