U.S. patent number 3,737,217 [Application Number 05/159,857] was granted by the patent office on 1973-06-05 for visual examination apparatus.
This patent grant is currently assigned to The United States of America as represented by the Administrator of the. Invention is credited to James W. Fitzgerald, Richard F. Haines, Salvadore A. Rositano.
United States Patent |
3,737,217 |
Haines , et al. |
June 5, 1973 |
VISUAL EXAMINATION APPARATUS
Abstract
An automated visual examination apparatus for measuring visual
sensitivity and mapping blind spot location including a projection
system for displaying to a patient a series of visual stimuli, a
response switch enabling him to indicate his reaction to the
stimuli, and a recording system responsive to both the visual
stimuli per se and the patient's responses, the recording system
thereby providing a correlated permanent record of both stimuli and
response from which a substantive and readily apparent visual
evaluation can be made.
Inventors: |
Haines; Richard F. (Palo Alto,
CA), Fitzgerald; James W. (Atascadero, CA), Rositano;
Salvadore A. (San Jose, CA) |
Assignee: |
The United States of America as
represented by the Administrator of the (Washington,
DC)
|
Family
ID: |
22574381 |
Appl.
No.: |
05/159,857 |
Filed: |
July 6, 1971 |
Current U.S.
Class: |
351/224; 351/237;
351/243; 600/558 |
Current CPC
Class: |
A61B
3/06 (20130101); A61B 3/024 (20130101) |
Current International
Class: |
A61B
3/06 (20060101); A61B 3/02 (20060101); A61B
3/024 (20060101); A61b 003/02 (); A61b 003/06 ();
A61b 005/00 () |
Field of
Search: |
;351/23,24,30,36
;128/2.1B,2.1R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wibert; Ronald L.
Assistant Examiner: Sacher; Paul A.
Claims
What is claimed is:
1. Visual examination apparatus, comprising:
light receiving means including, a display screen for displaying
visual stimuli to a patient, and photosensitive means responsive to
light and operative to generate binary coded decimal signals which
control the meridian location and direction of the stimulous
image;
light projecting means for projecting stimulus images onto said
signal display screen, and for projecting control images
commensurate with said stimulus images onto said photosensitive
means;
said light projecting means including means for projecting light
through a filmstrip containing said stimulus images and said
control images and onto said light receiving means;
patient response means for developing response signals commensurate
with said visual stimuli as perceived by said patient;
means responsive to said stimuli signals and said response signals
and operative to develop recorder control signals; and
a recorder responsive to said recorder control signals and
operative to provide a comparable record of said visual stimuli and
the patient response corresponding thereto.
2. Visual examination apparatus as recited in claim 1 and further
comprising means for projecting one or more fixed position fixation
images onto said display screen.
3. Visual examination apparatus as recited in claim 1 wherein said
means responsive to said signals includes electronic control
circuitry responsive to said stimuli signals and said response
signals and operative to develop a first set of said recorder
control signals, said control circuitry being further responsive to
said stimuli signals to develop a second set of said recorder
control signals.
4. Visual examination apparatus as recited in claim 3 wherein said
recorder includes a pair of trace developing means responsive to
said first set of control signals, and positioning means responsive
to said second set of control signals and operative to position
said trace developing means.
5. Visual examination apparatus as recited in claim 1 wherein said
light projecting means includes a cathode ray tube and programmable
means for driving said cathode ray tube in accordance with a test
program.
Description
The invention described herein was made by employees of the United
States Government and may be manufactured and used by or for the
Government for governmental purposes without the payment of any
royalties thereon or therefor.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to visual examination
apparatus and, more particularly, to an automated visual
sensitivity tester for examining the eyes of a human being to
determine visual field sensitivity and blind spot size, shape, and
position.
2. Description of the Prior Art
Because of the rather substantial dependence of an astronaut on his
visual perception and the high degree of likelihood that such
perception might change without notice during long term space
flight, it is important that vision testing means be provided for
enabling him to periodically test and evaluate his visual
capabilities.
A test of visual sensitivity during long durations of space flight
is important because of the possibility of the occurrence of
changes in the transparency of the eye's optic media due to the
impingement of various ionizing radiations, foreign matter, or
cataract development; changes in the neural, biochemical and/or
photochemical processes which underlie visual sensitivity; and
changes in the visual perception due to a wide range of retinal and
central nervous system dysfunctions which effect sensitivity. In
addition, mapping the size, shape, and location of the blind spot
is of value not only in determining the state of retinal (thus
visual) function near the perimeter of the blind spot, but in
providing an indication of changes in intraocular pressure. It is
well-known that an intraocular pressure change may indicate such
things as the presence of ocular inflammmation, changes in blood
pressure, elasticity of retinal vessels, body temperature,
alkalinity, and osmotic pressure of the cardiovascular system,
closure or clogging of the anterior ocular chamber, or variation of
the volume of any of the intraocular areas.
Presently, no fully automated visual field testing or blind spot
mapping apparatus is commercially available. Although there are
available of number of hand-operated visual "perimeters," such as
the Goldmann Perimeter and the Ferree-Rand B & L Semi-Automatic
Recording Perimeter, these devices require that an operator slowly
manually move the visual stimulus over the patient's visual field.
Furthermore, these devices are difficult to use; require a
moderate-to-high degree of operator training in the use of the
tester; are relatively expensive; and produce relatively poor
correspondence between the test spot's location and its final
recorded position in the patient's visual field.
Among the performance criteria for such a vision tester are:
adequate sensitivity to changes in visual performance that
accompany the various stresses encountered in space flight;
sufficient comprehensiveness to detect the possibility of changes
in visual functions other than those expected; and adequate
diagnostic value--the tester should not only detect a dysfunction,
but should provide an indication of the extent of its
development.
SUMMARY OF THE PRESENT INVENTION
It is therefore an object of the present invention to provide a
convenient and practical means for automatically measuring the
visual sensitivity of the patient's eyes, and for accurately
delineating the size and shape of the blind spots of the patient's
eyes.
In accordance with the present invention, an automated visual
examination apparatus is provided which includes a movie projector
for presenting dynamic visual stimuli, an infinity collimating
lens, a head positioning support, a response button, an electronic
control unit, and a two-pen XYY' response plotter. In the preferred
embodiment, a 10-arc-minute diameter dim white spot of light is
made to travel across a viewing screen along each of 12 meridians
which are separated by 30.degree. arcs in the patient's frontal
plane and to randomly disappear and reappear during its traverse.
The patient is instructed to press the response button each time
the spot disappears, and to release the button when the spot
reappears so that his responses can be recorded by one of the two
pens of the plotter. The second pen records the on-off status and
movements of the visual stimulus. Various dysfunctions can then be
assessed by comparing the plotted stimulus and response traces.
The present invention is sensitive to the presence of such
dysfunctions as scotomata, glaucoma, and changes in retinal
sensitivity which are of such magnitude as to make the dynamic
visual stimuli invisible, and can be used to perform other visual
examinations by the preparation of other stimulus films, such as
glare recovery (using a strobe flash tube addition), motion
perception thresholds, visual tracking ability (using an eye
tracking monitor addition), visual acuity (using an appropriate
stimulus pattern on the film), critical fusion frequency
measurements, and color perceptibility.
Among the advantages of the present invention are that all
experimental randomizations, light level controls, and other
necessary and critical visual characteristics of the stimulus are
automatically controlled; use of the device does not require or
involve any verbal patient responses; all electronic components are
responsive to the stimulus display and patient response button; use
of specially prepared test films makes it possible to randomize the
presentation order of the visual stimuli; and the device makes it
possible to easily and accurately locate and stabilize the
patient's head and eyes during the testing period.
In addition to the space travel applications, an automated visual
sensitivity tester having the characteristics described above would
also have valuable clinical application in ophthalmological and
optometric practice due to its ease of operation, high reliability,
and completely automated nature.
IN THE DRAWINGS
FIG. 1 is a schematic diagram illustrating the basic operative
functions of a preferred embodiment of the present invention.
FIG. 2 is a diagram further illustrating the stimulus display
screen of FIG. 1.
FIG. 3 schematically illustrates an alternative embodiment of the
present invention.
FIG. 4 illustrates an automated visual sensitivity testing system
in accordance with the present invention.
FIG. 4a further illustrates the X-Y coordinate selector shown in
FIG. 4.
FIG. 5 illustrates the results of a visual sensitivity test for a
normal eye using the apparatus of the present invention.
FIG. 6 illustrates the results of a blind spot mapping of a normal
eye using apparatus in accordance with the present invention.
FIG. 7 illustrates the results of a visual sensitivity test for a
glaucomatous eye using the apparatus of the present invention.
FIG. 8 illustrates the results of a blind spot mapping of a
glaucomatous eye using apparatus of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1 of the drawings which is a schematic
illustration (from the top) of a visual sensitivity tester in
accordance with the present invention, it will be noted that the
apparatus includes a projection system 10 having a suitable housing
(not shown), a signal conditioning unit 12 jointly responsive to
stimulus signals generated by projection system 10 and response
signals input by a patient via the response switch 14, a control
unit 16, and a multiple pen X-Y recorder 18.
Projection system 10 is comprised of a vertically mounted panel 20
having a circular aperture 21 in its midportion to which a
semi-transparent, semi-diffuse display screen 22 is affixed. In
addition, a pair of photocells 24 are disposed in each of the upper
and lower corners of panel 20 outside the bounds of screen 22.
Affixed to the front side of panel 20 is a shroud 26 for shielding
that side of screen 22 from external light. Shroud 26 also serves
as a support for a viewing lens 28 and filter unit 29 through which
an eye 27 under test views screen 22. A mirror 30 and three visual
fixation cross projectors 32, 34, and 36 are disposed opposite the
rear side of panel 20. The fixation projectors may either be
positioned above and behind mirror 30, as indicated, or may be
suitably positioned on the front side of mirror 30 with their light
beams being reflected by mirror 30 onto screen 22. A motion picture
projector 40 including a light source 42, condensing lens 44 and
projection lens 46 is also provided for projecting images from a
movie filmstrip 48 onto the rear side of panel 20 via reflection
from mirror 30.
In accordance with the present invention, the image projected from
filmstrip 48 includes a stimulus image, in the form of a moving
white spot of light, and a plurality of small coded spots of light
disposed at fixed positions outside of the field falling on screen
22. The moving white spot is caused to sequentially move in a
predetermined manner over 12 meridians lying within that portion of
the image which is projected onto screen 22, while the coded spots
of light are projected outside of screen 22 to fall on the
photocells 24. The coded light spots cause photocells 24 to
generate binary coded decimal signals corresponding to the stimulus
image's meridian location, direction along each meridian, and
on-off status.
In operation, the patient is instructed to fix his gaze upon a
fixation cross at, for example, the point 50 (as projected by
projector 34) on screen 22, and is further told to press button 15
of response switch 14 during the times that he does not see a white
dot moving across screen 22, and to release button 15 during times
that he is able to see the moving white dot. As depicted in FIG. 2,
the moving white dot 52 is projected onto screen 22 by projector 40
and is caused to move first along one meridian and then another
toward, or away from, fixation cross 50. During the time that the
spot generating beam 54 (FIG. 1) is swung over the angle .alpha.
(causing spot 52 to sweep over a single meridian), it will be
caused to momentarily disappear during random portions of its sweep
transverse. As spot 52 is swept slowly over each of the 12
meridians, spot presence and location data in the form of binary
pulses are generated by photocells 24, and this data is input to
signal conditioner 12. Switch 14 supplies the patient response
input signals to signal conditioner 12. The conditioned signals
developed by conditioner 12 are then fed into control unit 16 which
in turn develops appropriate control signals for energizing the ink
pens of recorder 18 so that both the white spot path and the
response thereto are recorded for evaluation.
As an alternative to the motion picture projecting embodiment of
FIG. 1, it will be appreciated that a cathode ray tube 60 can
likewise be used to generate similar dynamic test images similar to
those projected in the previous embodiment. In this embodiment, a
program source 62, such as a digital computer, a video tape player,
a punched paper tape player, or some other suitable source of
stimulus signals, is provided for converting a prerecorded test
program into input signals suitable for driving the CRT control
electronics 64 which, in turn, cause CRT 60 to develop the desired
test display. The program source 62 functions to replace the
conditioned photocell signals from signal conditioner 12. The
vertical (Y) and horizontal (X) inputs of the CRT control
electronics 64 are connected in parallel with the X-Y recorder
inputs. This results in the simultaneous X-Y control of the CRT dot
and the pens of the X-Y recorder. The CRT dot and pens move in
synchronism to provide the test image and record the results,
respectively.
In FIG. 4 of the drawings, there is shown a more detailed preferred
embodiment of an automated visual sensitivity tester in accordance
with the present invention which includes a rear projection,
cartridge loaded, super 8mm movie projection unit 110, a control
unit 112, and a response plotter 114. Projection unit 110 includes
a display panel 116 having a transparent, semi-diffuse projection
screen 118 and eight photocells 120 mounted two in each corner as
schematically illustrated in FIG. 1. Beneath display panel 116 and
to the right side of the instrument cabinet 121, a film cartridge
insertion slot 122 is located for receiving a film cartridge or
cassette 124.
At the front of the cabinet beneath slot 122, a slanted control
panel 126 is provided which includes an ON lever 128 for turning
the projector ON, an OFF button 130 for turning the projector OFF,
a visual fixation projector control toggle 132 which allows the
visual fixation projectors to be turned ON independently of the
projector, a visual fixation cross selector knob 134 which is a
three-positioned switch for individually turning on each of three
visual fixation projectors, a cable plug 136 for connecting the
hand-held response switch 138 to the apparatus, an image focus knob
140, and a movie projector framing control knob 142 for adjusting
the stimulus' vertical screen position. Directly beneath control
panel 126 four shelves 144 are provided for storing extra film
cartridges.
An aluminum mask, or shroud 146 is mounted over display panel 116
on the patient's side of screen 118. Although shroud 146 extends
outside the locus of photocells 24, the viewing lens 28 limits the
field of view to a 60.degree. arc-diameter including screen 118.
The eight photocells 120, which may for example, be of the Clairex
type CL-905-L are located outside of this field of view on the
patient's side of panel 116. Mounted rigidly to the front of shroud
146 is a viewing lens and filter mount 148 through which the
patient 150 views screen 118. In order to insure that the patient's
head is properly centered behind the viewing aperture (lens) 152,
an adjustable dental impression bite board 154 and adjustable
forehead rest 156 are provided. However, as an alternative, a chin
rest and a curved padded support at the temples could also be
used.
Within cabinet 121 are included film projecting components such as
the lamp 160, condensing lens (not shown), projecting lens 162, a
small-sized reflector 164, a medium-sized reflector 166, a
large-sized reflector 168, and suitable film drive apparatus (not
shown). Note that when cassette 124 is included in the projector,
the small reflector 164 is positioned behind film 170 for
reflecting the light passing through film 170 up to projection lens
162. The projector is capable of projecting images from both color
and black-and-white movie filmstrips onto screen 118. Since the
film 170 contained within cassette 124 is a continuous loop, no
threading is required and the film can be stopped and the cartridge
removed from the tester at any time. Three visual fixation cross
projectors 172 are also provided within cabinet 121 and are mounted
in such a position that they will project into mirror 168.
Projectors 172 project red crosses of 10 minute-arc bar length upon
viewing screen 118, at its middle and about 15.degree. arc to the
left and right of the middle cross, respectively. The projectors
172 may, for example, include a 6.3 volt lamp, opal glass diffuser,
photographic negative of a cross, focusable achromatic lens, and a
red No. 24 Wratten filter. Lamp luminance is controlled by
adjustable resistors (not shown).
Projection unit 110 also includes signal conditioning circuitry
(not shown) which converts the output of photocells 120 into binary
signals including: four binary coded bits denoting one of 12 preset
stimulus meridians; two binary coded bits denoting stimulus
direction of travel (IN or OUT along a given meridian) and a HOLD
or RESET command; one binary coded bit denoting stimulus condition
(light ON or OFF); and a sync bit which indicates whether the lamp
160 is ON or OFF. In addition to the photocell input, the patient's
response signals are also input to the signal conditioning
circuitry.
The conditioned signals are then fed into the programming circuitry
180 of control unit 112 which includes a relay interface 182, a
decode matrix 184, and a number of reed relays 186. Relay interface
182 develops a stimulus signal on line 188, a patient response
signal on line 190, and binary coded control information which is
coupled into the decode matrix 184 on line 192. The decode matrix
unit 184 develops OUT, IN, HOLD, and RESET signals on the lines
194, 196, 198, and 200, respectively, as well as actuating signals
for the reed relays 186. Lines 194 and 196 out of decode matrix 184
are coupled into the OUT and IN terminals, respectively, of a
voltage regulator 202 of the output circuitry 204 which, in
addition, includes an integrator 206, buffer amplifiers 108 and
210, and an X-Y coordinate selection unit 212. The HOLD and RESET
signals on lines 198 and 200, respectively, are coupled into
integrator 206 and the decoded stimulus information is used to
drive relays 186 which perform a channel selection function for X-Y
coordinate selection unit 212. Unit 212 develops an X-axis output
on line 214 and a Y-axis output on line 216 which respectively
energize the X- and Y-axis drive units of plotter 114.
More specifically, the binary coded stimulus information is decoded
by matrix 184 and used to drive reed relays 186 to control an
analog voltage for input to unit 212. The stimulus direction of
travel (IN or OUT) signals allow a plus or minus regulated voltage
from regulator 202 to drive the output of integrator 206 toward a
first voltage (+5 volts) or back to a second voltage (0 volts). If
the first command is OUT, the output of integrator 206 will
initially move toward +5 volts. This command will then be followed
by a HOLD command and then by an IN command. The ramp output
voltage will then move toward 0 volts. If the sequence is reversed
(an IN command followed by a HOLD, followed by an OUT command), the
output of integrator 206 will move from 0 volts toward -5 volts
followed by a HOLD condition then back toward 0 volts. The result
of using both of these sequences is to provide 24 unique radial pen
excursions, along the 12 preprogrammed meridians.
The "ramp" output voltage developed by integrator 206 on line 207
is buffered by the two amplifiers 208 and 210 to develop plus and
minus ramp voltages on lines 209 and 211. The plus and minus ramp
voltages are fed into X-Y coordinate selector 212 which, as better
illustrated in FIG. 4a, includes two potentiometers 213 per
meridian that are used to preset each of the X and Y coordinates of
pen travel. Toggle switches 215 are used to select the sign of the
sine or consine functions for locating the meridian within any of
the four projection screen 118 quadrants. For example, if the pens
of response plotter 114 are supposed to move along the 30.degree.
meridian (all meridians are measured from the 12 o'clock position
in the clockwise direction) the X-channel potentiometer is set for
+0.866 and the Y potentiometer for +0.500. These values represent
the cosine and sine of 30.degree., respectively. An OUT command
will then cause the pens to move out from the center of the data
recording sheet along the 30.degree. meridian. If, however, an IN
command is initiated first, the pen will travel along a 210.degree.
meridian (i.e., 180.degree. from the 30.degree. meridian). Although
the response plotter's pens are driven in parallel, the patient's
response switch 138 and the stimulus OFF/ON information cause the
pens to drop onto the paper independently.
In operation, an eye positioning plate (not shown) is inserted into
a slot just behind the viewing lens 152, and the visual fixation
cross selector knob 134 is turned to the top left position, if the
blind spot of the right eye is to be tested; to the middle
position, if the visual sensitivity of either eye is to be tested;
and to the top right position, if the blind spot of the left eye is
to be tested. The patient is then instructed to bite onto bite
board 154 (or place his chin into a chin rest) and to loosen the
horizontal and vertical adjustment knobs 155. He then slides bite
board 154 horizontally and vertically until the fixation cross is
seen through a small hole in the eye positioning plate, whereupon
he tightens the adjustment knobs 155 finger tight and then adjusts
the forehead rest 156. The eye positioning plate is then removed,
and the test film is turned on to begin the test.
The patient is then told to hold the response switch 138 in his
preferred hand, resting his thumb on the button, and to maintain
his gaze directly upon the red cross and note the small white spot
of light which will travel slowly across the field of view in
various directions, and which will, from time to time, disappear.
It is also pointed out that to make these visual tests valid, it is
important that visual fixation (i.e., direction of gaze) be
maintained on the small fixation cross projector on the screen
throughout the test. The patient is to merely press his finger
button as soon as the white light disappears and to release the
finger button the instant the white light reappears.
In accordance with one visual sensitivity testing scheme, the spot
traverses radially outwardly or inwardly from the screen center
point to make interrupted traces such as those illustrated in FIG.
2 (see also FIGS. 5 and 7). The outer portions of the program film
170 simultaneously project the coded light spots onto the several
photocells 120 which generate signals that, when fed into control
unit 112, actuate the stimulus recording pen of plotter 114. If the
patient sees the spot disappear and properly depresses the button
of switch 138, patient's response signals will also be generated
for actuating the second pen of plotter 114 so as to inscribe a
parallel mark (shown dashed in FIGS. 5 and 7) next to the stimulus
marks. However, when the patient sees the spot reappear on screen
118, he will, of course, release the control button. The
correspondence between the two parallel marks on the plot will
indicate his visual deficiency.
The visual sensitivity of a patient having a glaucomatous
dysfunction is illustrated in FIG. 7 of the drawings which
indicates a large scotoma in the upper right-hand visual field
along 30.degree., 60.degree., and 90.degree. meridians from the
foveal boundary out to a 30.degree. arc radius limit. This may be
compared with the test results of a patient having normal visual
sensitivity and reaction times to the disappearance and
reappearance of the moving white spot of light as shown in FIG.
5.
In administering the blind spot mapping test (see FIGS. 6 and 8),
the patient is told to position his head as before, to fix his gaze
upon the small cross on the screen, and to press the finger button
whenever the moving white spot disappears and release the finger
button when the spot reappears. In this case, however, the moving
white spot of light is never turned off as it traverses the
patient's field of view. It disappears only when its image falls
upon the blind spot or other areas of retinal insensitivity. By
using one of the visual fixation crosses located to one side of the
center of the viewing screen and by causing the moving white spot
to traverse along each of the 12 meridians centered upon the
viewing screen (where the blind spot is also imaged), the image of
the white spot of light will traverse the blind spot's boundary.
This produces a polar coordinate graphic plot of the boundary of
his blind spot. Because the white spot of light moves both OUT and
IN along each meridian (thereby plotting the blind spot boundary
from each direction in 12 locations), an experimenter makes a small
vertical mark when the response plotter's pen indicates that the
patient has pressed his response button for the IN direction of
travel. The actual blind spot boundary is taken as the average of
the OUT and the IN pen marks. In FIG. 6, test results for a normal
right eye are illustrated, while in FIG. 8 the results are shown
for an individual (the same patient as in FIG. 7) having a
glaucomatous dysfunction.
Since the recorded data provided by the present invention is in the
form of stimulus traces and associated response traces, it will be
appreciated that the test results need not necessarily be recorded
in polar coordinate form, but could likewise be recorded in strip
chart form, or the like, where a switch means of reference is
provided. For example, if in the case of visual sensitivity
examination, the pen traces are made by fixed position pens which
record on a moving strip of paper and some type of marker is
provided to indicate which traces are included in each stimuli
meridian and their respective radial positions in a given meridian
or other portion of a focal field, the data would be just as
interpretable as in the illustrated polar type of graph.
From these examples, the utility of the present invention will be
readily appreciated by those skilled in the art and certain
modifications and improvements thereof will no doubt become
apparent. It is therefore to be understood that the above
disclosure is by way of illustration only and is not intended to be
limiting. Accordingly, the appended claims are intended to cover
all such modifications and improvements as fall within the true
spirit and scope of the invention.
* * * * *