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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to ophthalmological instruments
and, more particularly, to a computer-controlled electro-optical
instrument designed to automate and quantify clinical examination of
pupillary responses and extrinsic eye muscle balance. The invention is
specifically directed to an optical system for such an instrument which
simultaneously focuses images of a patient's left and right pupils on
different areas of a common photosensitive image plane of a video camera.
The two images are located close to one another and greatly magnified on a
display screen to allow the physician to better observe and analyze pupil
response to stimuli.
2. Description of the Prior Art
The iris of the eye is (in humans) a ring-shaped colored muscle. The hole
in the center of the iris, called the pupil, normally appears black
because the surfaces behind it reflect back to an observer much less light
than does the surrounding iris. When the eye is suddenly exposed to light,
certain of the muscle fibers in the iris contract, causing the pupil to
become smaller, or constrict. The pupils also constrict when a near object
is viewed, and their diameter is also determined continuously by certain
aspects of psychological state, for example, fear. Pupil diameter is also
affected by the actions of many drugs, both systemic drugs and those
applied directly to the eye.
The overall physiological system that controls pupil size includes many
components, and because the various components may be affected in various
ways by different diseases, toxins, tumors, and the like, disorders are
often reflected in abnormal pupillary responses. Therefore, examination of
the responses of the pupillary system is an important part of most
neurological and ophthalmological medical examinations. To perform an
examination of pupil responses, the physician dims the room lights,
illuminates one eye and then the other with a small light, and observes
the responses. This technique, even when performed by the most careful
observer, lacks much in accuracy and provides no quantitative or permanent
record of the results.
Various systems are known in the prior art which automate the examination
of pupil function and provide a quantitative result. For example, U.S Pat.
No. 3,036,568 to Stark shows a pupillometer which monitors the response of
an eye to light stimulus. An infrared light source is used to illuminate
the eye. A glow lamp provides a visible light stimulus and, as a result of
a constriction of the pupil, the light reflected from the iris to an
infrared sensitive device varies. The output of the infrared sensitive
device is supplied to a chart recorder. In U.S. Pat. Nos. 3,533,683 and
3,533,684, Stark et al. show a dynamic pupillometer using a television
camera system in which an infrared light source, a visual light stimulator
and a television camera system are all directed at the eye of a patient.
As in the previous Stark patent, the pupil contracts upon visual light
stimulation thus allowing the iris to reflect more infrared light, but in
this case the infrared light is detected by the camera. The instantaneous
pupil size is determined by counting television scan lines.
Other examples of automated pupil function examination systems are
disclosed in U.S. Pat. No. 3,966,310 to Larson which shows a hand held
pupillometer and U.S. Pat. No. 4,755,043 to Carter which shows a digital
portable scanning pupillometer.
It is also known to automate other eye examination procedures. For example,
U.S. Pat. No. 4,370,033 to Kani et al. discloses an eyeball examining
device which is used to analyze the eye retina. A visible light beam is
projected onto any area of the eye retina, and a magnified image of the
eye retina is displayed on an infrared television monitor. U.S. Pat. No.
4,618,230 to Ens et al. discloses a computer controlled visual stimulator
that obtains an electroretinogram by an automated process.
While there exist several systems that address the problem of automating
the examination of the pupil function, the scope of the examination is
relatively limited and requires a highly skilled person to operate the
system and analyze the results.
SUMMARY OF THE INVENTION
It is therefore a general object of the present invention to provide a
highly automated, multi-function system for the quantitative examination
of pupil function.
It is a more specific object of this invention to provide a binocular
optical system for pupil function analysis which measures both pupils and
extracts most clinically significant pupil system measures with a minimum
of tests.
It is yet another object of the invention to provide an optical system for
an automated pupil function analysis capable of partial stimulation and
comparison of responses among regions of the retina and measures and
analyzes afferent defect and swinging flashlight data automatically.
The pupil function analyzer has three major subsystems; an electro-optical
system, an electronic interface system and a computer/software system. The
electro-optical system can, in turn, be described in terms of three
subsystems; one that delivers controlled lights to the patient's eyes,
another that forms images of the two pupils on a television camera, and a
third that moves the optics to maintain alignment with the patient's eyes.
The electronic interface system converts signals from the television
camera into digital signals to be read by the computer and also responds
to the computer to energize LEDs for optical stimuli and to move motors
for the maintenance of optical alignment. The computer/software saves and
analyzes the signals sent by the electronic interface, controls the
alignment motors, and provides an operator interface, so that the operator
can select tests and examine the results.
The operator selects a desired test or set of tests from a menu displayed
on a display screen, such as a CRT. The patient then places his or her
head in a headrest, and an image of the region of one of the patient's
eyes appears on the display screen. The operator uses a control device,
such as a light pen which cooperates with the display screen, to move the
image of the eye until it is roughly centered on a cross-hair provided for
the purpose. The process is repeated for the other eye. The operator then
presses a start button, and the test proceeds automatically. During the
test, the instrument automatically aligns the optics precisely on both
eyes and maintains alignment even if the patient's eyes moves, introduces
lights into the eyes according to the sequence selected by the operator,
measures the diameters and the positions of both pupils, and saves all the
measurements. When the test is complete, a tone sounds indicating
completion of the test and that the patient may move away from the
instrument, and the operator selects the next step from a menu. This step
can be to display any or all results, to print the results, and/or save
the results on floppy disk for storage in the patient's file.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects, aspects and advantages will be better
understood from the following detailed description of a preferred
embodiment of the invention with reference to the drawings, in which:
FIGS. 1A and 1B are, respectively, a patient elevation view and a side view
of the basic pupil function analyzer according to the invention;
FIG. 2 is a perspective view of the pupil function analyzer showing an
attached operator display monitor and light pen;
FIG. 3 illustrates an initial display screen which is displayed when the
instrument is first turned on;
FIG. 4 illustrates a pull down menu which is displayed when the TEST
command is selected from the command bar;
FIG. 5 illustrates a data entry screen for entering a patient's age before
beginning a test;
FIG. 6 illustrates an initial screen showing the test which has been
selected;
FIG. 7 illustrates the screen of FIG. 6 in which the BEGIN command has been
selected;
FIG. 8 illustrates the video screen used to align the images of the
patient's eyes prior to the test being run;
FIG. 9 illustrates the video screen during the swinging impulse test;
FIG. 10 illustrates the video screen during the impulse test;
FIG. 11 illustrates the video screen during the perimetry pupil size test;
FIG. 12 illustrates the screener summary data screen;
FIG. 13 illustrates the first of two graphical data screens for the
swinging impulse test;
FIG. 14 illustrates the screen of FIG. 13 scrolled to the right;
FIG. 15 illustrates the second of the two graphical data screens for the
swinging impulse test;
FIG. 16 illustrates the first of three data screens for the impulse
response test;
FIG. 17 illustrates the screen of FIG. 16 scrolled to the right;
FIG. 18 illustrates the second of the three data screens for the impulse
response test;
FIG. 19 illustrates the third of the three data screens for the impulse
response test;
FIG. 20 illustrates the data screen for the perimetry pupil size test;
FIG. 21 illustrates the overlying pull down window which is displayed when
the TEST command is selected;
FIG. 22 illustrates the dialog box for configuring stimulus fields;
FIG. 23 illustrates the custom stimulus dialog box for configuring the
stimulus for the Hippus test;
FIG. 24 illustrates the initial screen for running the Hippus test;
FIG. 25 illustrates the selection of the BEGIN command for the Hippus test;
FIG. 26 illustrates the video screen used to align the images of the
patient's pupils on the video screen;
FIG. 27 illustrates the video screen during the Hippus test;
FIG. 28 illustrates the graphical data screen showing the results of the
Hippus test;
FIG. 29 illustrates the screen of FIG. 28 scrolled to the right;
FIG. 30 illustrates the pull down window which is displayed when the
LIBRARY command is selected;
FIG. 31 illustrates the dialog box which is displayed for entering the
patient's ID;
FIG. 32 illustrates the pull down window which is displayed when the
LIBRARY command is again selected for ending a session;
FIG. 33 is a schematic diagram showing the optical system viewed from the
top;
FIG. 33A is a plan view showing the arrangement of the lenses L.sub.1 and
L.sub.2 ;
FIG. 34 is a schematic diagram showing the optical system viewed from the
left side;
FIG. 35 is a perspective view of the overall mechanical assembly including
left and right actuators;
FIG. 36 is a perspective view of the left light box assembly;
FIG. 37 is an exploded view of the left scope assembly;
FIG. 37A is an exploded view of the left scope box assembly;
FIG. 37B is an exploded view of the left piston assembly;
FIG. 38 is an exploded view of the right scope assembly;
FIG. 38A is an exploded view of the right scope box assembly;
FIG. 38B is an exploded view of the right piston assembly;
FIG. 39 is an exploded view of the focusing mechanism for the left
actuator;
FIG. 40 is a perspective view of the left actuator;
FIG. 40A is a perspective view of the base assembly for the left actuator;
FIG. 40B is a perspective view of the base assembly of FIG. 40A with a
pivoted vertical plate added;
FIG. 40C is a perspective view of the base assembly of FIG. 40B with a
subframe added;
FIG. 40D is a perspective view looking into the subframe assembly shown in
FIG. 40C;
FIG. 41 is a block diagram showing the electronics of the system;
FIG. 42 is a detailed block diagram of a component of the interface
electronics shown in FIG. 41;
FIG. 43 is a graphical representation of the analog video signal produces
when a patient's pupils are scanned;
FIG. 43A is an enlarged graphical representation of a leading edge of the
video signal;
FIGS. 44, 45 and 46, taken together, are a flow diagram showing the logic
of the data acquisition and tracking software;
FIGS. 47 to 54 are the flow diagrams showing the logic of the software
which form the menu and dialog box interface for the system in which
FIG. 47 is the flow diagram for the startup procedure,
FIG. 48 is the flow diagram for the PATIENT command selected from the
command bar of the display,
FIG. 49 is the flow diagram showing the logic of the TEST command selected
from the command bar of the display,
FIG. 50 is the flow diagram showing the logic of the BEGIN command selected
from the command bar of the display,
FIG. 51 is the flow diagram showing the logic of the DISPLAY command
selected from the command bar of the display,
FIGS. 52A, 52B, 52C, and 52D are the flow diagrams showing the logic of the
LIBRARY command selected from the command bar of the display,
FIG. 53 is the flow diagram showing the logic of the HELP command selected
from the command bar of the display, and
FIG. 54 is the flow diagram showing the logic of the PAGE command selected
from the command bar of the display; and
FIGS. 55 to 64 are flow diagrams showing the logic for the several tests
performed in which
FIG. 55 is the flow diagram for the swinging flashlight test,
FIG. 56 is the flow diagram for the swinging impulse test,
FIG. 57 is the flow diagram for the hippus test,
FIG. 58 is the flow diagram for the perimetry test,
FIG. 59 is the flow diagram for the step response test,
FIG. 60 is the flow diagram for the impulse test,
FIGS. 61A and 61B, taken together, are the flow diagram for the relative
afferent defect test,
FIG. 62 is the flow diagram for the cover/uncover test,
FIG. 63 is the screener flow diagram, and
FIG. 64 is the demo flow diagram.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
Referring now to the drawings, and more particularly to FIGS. 1A and 1B,
there are shown, respectively, an elevation view on the patient's side of
the instrument and a side view on the operator's side of the instrument.
The basic instrument is housed in a compact case 10 having a small
footprint so that it may be placed on a desktop. On the patient's side,
FIG. 1A, there is a slight protrusion 12 with an aperture 14 into which
the patient is instructed to gaze. The patient's head is positioned by a
nose and brow piece 16 suspended within the aperture 14. On the operator's
side, FIG. 1B, there is an on-off switch 18 and a floppy diskette drive
20. While data for each patient will normally be printed on paper by a
printer (not shown) attached to the system, data may also be stored on a
diskette for storage in a patient's folder.
A separate display 22 and light pen 24, as shown in FIG. 2, is provided for
the operator of the system. The display may be any display compatible with
the NTSC television standard and capable of supporting overlaid computer
generated graphics. In a preferred embodiment, the display is a
conventional IBM Personal Computer compatible computer monitor supporting
both the color graphics adapter (CGA) and enhanced graphics adapter (EGA)
standards, the former being compatible with the NTSC television standard.
The display 22 is connected to the instrument by a cable 26 allowing the
display to be placed at a convenient location for use by the operator. It
will be understood, however, that the display 22 may be made integral with
the instrument. For example, the display could be incorporated into the
area 28 (shown in FIG. 1B) on the side of the case 10 or into the back of
the case as generally indicated by the reference numeral 30.
The light pen 24 is the operator's input device. The instrument software
generates screens or menus on the display 22 from which the operator can
select various choices or into which the operator can input data by means
of the light pen 24. For example, when numeric data, such as a patient's
identification number (ID), needs to be input, a numeric keypad is
displayed and the operator simply selects the numbers on the keypad using
the light pen. In the same manner, if it is desired to input alphabetic
data, a keyboard may be displayed. As will be described in more detail
hereinafter, the light pen is also used for moving images of the patient's
eyes so that those images are aligned with cross hairs on the display
screen.
It will be understood by those skilled in the art that various operator
input devices may be used in place of the light pen 24 and display 22. For
example, a hardware keyboard and keypad could be used to input
alphanumeric data. A hardware cursor positioning device such as a mouse, a
track ball or a joy stick could be used to position the images of the
patient's eyes on the cross hairs. While such hardware is conventional and
well known, the approach taken in the design of the preferred embodiment
of the invention is make the instrument as simple to use by an untrained
operator as possible. The light pen 24 has been found to be a very easy to
use input device which is easily mastered without intimidating the user.
Of course, the light pen itself could be replaced by the operator's finger
if the display 22 incorporates a touchscreen.
The approach taken in the design of the software for the instrument is to
provide a "point-and-shoot" graphical user interface (GUI) with dialog
boxes and pull down windows as pioneered by the Xerox.RTM. Star computer
and made popular by the Apple.RTM. Macintosh.TM. computer. This is best
illustrated by way of example.
When the instrument is first turned on, the screen shown in FIG. 3 is
displayed. It will be observed that this screen includes a command bar 32
along the top in which are displayed the commands which are currently
active in the system. This initial screen displays a dialog box 34 which
requests the operator to verify the computer clock data and time and
displays the date and time with two "buttons". These are a RESET button 36
and an OK button 38, either of which the operator can select with the
light pen 24. It is important to have the correct date and time because
patient data is date stamped.
Assuming the operator selects the OK button 38, the dialog box 34 will
disappear. The operator may next want to test a patient, and this is done
by selecting TEST in the command bar 32 causing a pull down window 40 to
be displayed as shown in FIG. 4. This pull down window provides a menu of
several tests from which the operator may choose. In the case illustrated
in FIG. 4 the screener test as been selected, as indicated by the reverse
highlight, by sliding the light pen 24 down to that part of the pull down
window and releasing the select button on the light pen. As will described
in more detail, the screener test is actually a plurality of tests
selected to generate a variety of data from a patient. In the preferred
embodiment, the screener test may include, for example, an impulse test, a
swinging impulse test, a perimetry pupil size test, and a cover/uncover
test. It is, of course, possible for the physician who uses the instrument
to specify a different combination of tests for the screener test.
When the screener test has been selected, the dialog box 42 is displayed as
shown in FIG. 5. This dialog box requests the operator to enter the
patient's age and displays a numeric keypad for that purpose. In the case
illustrated, the operator has used the light pen 24 to select the numbers
"2" and "4", and the age "24" is displayed at the top of the keypad. If an
error has been made, the operator can select the CANCEL button 44, but in
this case, the OK button 46 has been selected as indicated by the reverse
highlight.
Once the patient's age has been entered, the screen shown in FIG. 6 is
displayed. This screen indicates that for this particular screener test,
the swinging impulse test, the impulse response test, the perimetry pupil
size test, step response test, and the cover/uncover test are performed.
FIG. 7 is similar to FIG. 6 except that the operator has now selected the
BEGIN command from the command bar 32, as indicated by the reverse
highlight. This causes the screen in FIG. 8 to be displayed. This screen
includes a pair of cross hairs 48 and 50. Below the cross hairs are a pair
of cursor pads 52 and 54, respectively, and between the cursor pads there
is displayed an ALIGNED button 56.
While not immediately apparent from the screens shown in FIGS. 7 and 8, the
protocol of the display changes when switching from the screen of FIG. 7
to the screen of FIG. 8. Up through the screen shown in FIG. 7, the
display is in enhanced graphics (EGA) mode, but the screen in FIG. 8 is in
color graphics (CGA) mode. EGA mode is a higher resolution mode and is
preferred for displaying text and graphics data. CGA mode is a lower
resolution mode, as may be observed by comparing the resolution of the
text in the command bars 32 in FIGS. 7 and 8, but its line and field
frequencies are compatible with the NTSC television standard. This mode is
required for displaying images of the patient's eyes, and particularly the
pupils. It will of course be understood that other high resolution display
protocols, such as video graphics array (VGA) or one of its higher
resolution variants, can be used for the display of text and graphics data
rather than the EGA standard. If a lower resolution display can be
tolerated, it is possible to use the CGA standard for all displays. It
will also be understood that the NTSC standard, which is the standard in
the United States, may be replaced by the PAL standard, which is the
standard from much of Europe, or another video standard. Of course, it is
understood that the display 22 used should be compatible with the
protocol(s) adopted and this is readily accomplished with one of the many
multi-sync monitors currently on the market.
Using the screen shown in FIG. 8, the operator first uses the cursor pads
52 and 54 to align the images of the patient's pupils on the cross hairs
48 and 50. Thus, if the image of the patient's right eye (left eye in the
display) needs to be moved to the right to center it on the cross hairs
48, the operator selects the right pointing arrow in the cursor pad 52
with the light pen 24. Left and up and down motions of the images are
accomplished in a similar manner. Once the images are roughly centered on
the cross hairs 48 and 52, the operator selects the ALIGNED button 56, and
at that point the instrument begins to automatically track the patient's
eyes, holding their images centered in the cross hairs 48 and 50. In
addition, when the ALIGNED button 56 is selected, the button 56, the cross
hairs 48 and 50 and the two cursor pads 52 and 54 are removed from the
display screen as they are no longer needed.
In FIG. 8, the patient's pupils 58 and 60 are indicated in dotted line as
centered on the cross hairs 48 and 50, respectively. At this point, it
should be observed that the pupils are magnified many times their actual
size and displaced close to one another, occupying a large portion of the
display screen. This allows the operator to observe with considerable
precision the reactions of the pupils to various stimuli during a test. If
the operator is a physician, this observed behavior will be of
considerable value, providing a useful supplement to the data later
displayed on the screen and printed.
Beginning in FIG. 9, the instrument automatically begins the test(s) which
have been selected. In FIG. 9, a message bar 62 is superposed above the
command bar 32 and informs the operator that the swinging impulse test is
in progress. The command bar includes only one command that the operator
can select, and that is the HALT command. The images of the patient's
pupils are shown in dotted line 58 and 60, and above them there are two
circles 64 and 66 divided into four quadrants each. These two circles are
used to indicate to the operator the nature of the stimulus being provided
to each of the patient's eyes. For example, in the swinging impulse test,
the circles would alternately flash, simulating a swinging light.
The next test is the impulse response test as indicated by the message bar
62 in the screen illustrated in FIG. 10. In this case the two circles 64
and 66 would flash simultaneously.
The next test in the example being described is the perimetry pupil size
test as indicated by the message bar 62 in the screen illustrated in FIG.
11. In this test, all four quadrants of the circles 64 and 66 are on. This
is indicated by the bright squares superimposed on the circles 64 and 66.
This also illustrates how the circles 64 and 66 appear in the previous two
tests except that the bright squares flash in a prescribed manner rather
than being on for the duration of the test. In addition, it should be
understood that the squares are themselves composed of four quadrants, and
it is possible to design the tests so that only one or less than all four
quadrants of each eye are stimulated. In that event, only the quadrant(s)
that is(are) stimulated are indicated by a bright square in the
corresponding quadrant of the circles 62 and 64.
Testing continues until the tests of the screener are completed. These
include the step response test, and the cover/uncover test in the example
being described. When the tests are complete for the screener, a buzzer,
bell or other audible signal sounds indicating that the patient may remove
his or her head from the aperture 14 of the instrument. An audible signal
is also generated between tests of the screener indicating that the
patient is allowed to blink. The display screen automatically switches
from the CGA mode to the EGA mode in order to display the test data in a
higher resolution mode. This data is generated by the microprocessor in
the instrument and displayed automatically when testing is complete. The
first screen displayed is illustrated in FIG. 12 and is a summary of the
screener tests including the patient's percentile for his or her age.
By selecting the PAGE command (which only appears if there is more than one
page to display), a graphical presentation of the results of the swinging
impulse test is displayed in the screen illustrated in FIG. 13. It will be
observed that the top part of the graph separately shows the reactions of
the right and left pupils correlated with the impulses. The graphs for the
right and left eyes are displayed in different colors (here, solid and
dotted lines) so as to better distinguish them. The difference between the
reactions of the right and left pupils is plotted in the lower part of the
graph. In this screen, there is also displayed a cursor bar 68, and by
selecting either the right or left arrows, the operator can scroll the
graph in either the right or left direction so as to be able to view all
the graphical data computed from the test. This is illustrated in FIG. 14
where the right cursor arrow has been selected. In addition, it will be
observed that this screen represents one of two pages of graphical data,
as indicated just above the cursor bar 68 at the right hand edge thereof.
In order to view the second page, the operator simply selects the PAGE
command in the command bar 32, and when this is done, the screen
illustrated in FIG. 15 is displayed.
The screen in FIG. 15 is a graph of the computed average for the swinging
impulse test with each eye displayed in a different color. At the top of
the screen, there is displayed "n=5" indicating that the displayed average
was computed from five swinging impulse repetitions. Actually, more
repetitions may have been run by the instrument, but due to detected
blinks by the patient, the other repetitions would not have been used in
the computation. This screen provides the operator with LEFT and RIGHT eye
buttons 70 and 72, respectively, for purposes of selecting which of the
graphs is displayed in black so that the operator can better distinguish
between the graphs.
The operator may now select the PAGE command from the command bar 32 to
display the computed graphical data from the next test. The first screen
for the impulse response test is shown in FIG. 16. This screen is similar
to the screen illustrated in FIG. 14, but for impulse response data, and
it too may be scrolled as indicated by the screen shown in FIG. 17. The
display of graphical data for the impulse test indicates that it is but
one of three pages. Therefore, the operator selects the PAGE command from
the command bar 32 to display the screen shown in FIG. 18. This is a
display of average impulse response computed from ten impulse response
tests. The third page of the impulse response data is shown in FIG. 19
which provides an impulse response summary for each eye.
The next test run by the screener was the perimetry pupil size test, and by
selecting the PAGE command from the command bar 32, the operator can
display the data from that test. This is illustrated by the screen shown
in FIG. 20 which provides the measured sizes of the pupils for the right
and left eyes.
Similar displays of data are made for the other tests of the screener. When
all the displays of data are concluded for the tests for the screener, the
operator may want to run a further test, perhaps because of something
observed in one of the screener tests. This the operator can do by simply
selecting the TEST command from the command bar 32. This causes the pull
down window 40 to be displayed over the current display as shown in FIG.
21. In the illustrated example, the operator now wants to run a Hippus
test as indicated by the reverse highlight in the pull down window.
The operator is next presented with a dialog box 72 to select the desired
stimulus as shown in FIG. 22. The operator has selected the "custom field"
stimulus for the Hippus test and now has the option to select either the
CANCEL or OK buttons 74 or 76. By selecting the OK button 76, the dialog
box 78 is displayed as shown in FIG. 23. This dialog box provides two
circles 80 and 82 corresponding to the circles 64 and 66 shown in FIG. 9,
10 and 11. The circles 80 and 82 are divided into to four quadrants as
illustrated, and each of these four quadrants can be selected by the
operator by using the light pen 24. Once the custom stimulus configuration
has been selected, the operator has selected the OK button 84 to implement
the custom stimulus for the Hippus test.
It will be understood from the foregoing description that similar stimulus
configuration can be provided for any of the other tests performed by the
instrument. In each case, the screen displayed in FIG. 23, but for the
particular test involved, is used to configure the stimulus fields.
Once the stimulus fields have been configured, the test list is displayed
as illustrated in FIG. 24. It will be observed that this screen is the
same as that shown in FIG. 6 except that the Hippus test has been added.
The screener tests are all displayed with a check mark to the left
indicating that these tests have already been run for this patient. In
FIG. 25, the operator selects the BEGIN command in the command bar 32 to
start the test.
At this point the display switches from EGA to CGA mode and again displays
the alignment video display screen, as shown in FIG. 26. Once the
patient's pupils 58 and 59 are aligned with the cross hairs 48 and 50, the
instrument runs the test as shown in FIG. 27. Note in this figure that the
circles 64 and 66 show the custom field stimulus used for this particular
test.
When the test is complete, the display switches back to the EGA mode, and
displays the computed graphical data as shown in FIG. 28. Again, this
display can be scrolled as shown in FIG. 29.
For our example, the operator is now finished testing the patient and wants
to store the data generated by the tests. Therefore, in FIG. 30, the
operator selects the LIBRARY command from the command bar resulting in
pull down window 85 being displayed. In this window, the operator selects
the SAVE command in the command bar 32. This causes the numeric keypad to
be displayed again in dialog box 88 with the request that the operator
enter the patient's ID as shown in FIG. 31. The operator has entered an ID
of 123456 and selected the OK button 90. The system saves the data to the
system hard disk and then clears the display screen. Now, to exit the
system, the operator selects the LIBRARY command again from the command
bar in the screen shown in FIG. 32 and then selects the SHUT DOWN option
in pull down window 91. This causes the system to return to the operating
system and the instrument can be turned off.
Having described the overall operation and the external interface of the
instrument, the internal subsystems which accomplish this operation will
now be described.
Optical Subsystem
FIGS. 33, 33A and 34 show the structure of the optical subsystem. It will
be noted that all of the system nearest the eyes is duplicated (in mirror
image) for each eye. The system features independent focus for each eye,
four quadrant illumination for each retina and a 30.degree. cone of vision
for each eye.
Considering first the portion of the optical system that delivers visible
lights to the patient's eyes, source S.sub.1 is a small, green light
emitting diode (LED) that flickers continuously. Aperture G.sub.1 lies in
the back focal plane of lens L.sub.1 so that the light from source S.sub.1
that passes through aperture G.sub.1 is collimated as it emerges from the
other side of lens L.sub.1 (see FIG. 33A). That light is reflected from a
"cold mirror" CM.sub.1 and enters the patient's right pupil. A "cold
mirror" is a mirror that reflects visible light, e.g., the screen light
from source S.sub.1, and transmits infrared light.
Light from source S.sub.1 passes through lens L.sub.1, reflects from cold
mirror CM.sub.1, passes through the right pupil, and falls on the right
retina. Lens L.sub.1 forms an image of source S.sub.1 in the center and
the plane of the right pupil, and the optics of the eye, in combination
with lens L.sub.1, form an image of aperture G.sub.1 on the retina. As a
consequence, because aperture G.sub.1 is round, the patient sees a small
flashing disk of green light. Similarly, light from the corresponding LED
source S.sub.3 and aperture G.sub.2 enters the left eye as from a source
at infinity. Because the paths followed by the light from these two LEDs
form the two cold mirrors CM.sub.1 and CM.sub.2, respectively, to the two
eyes are parallel, the two apertures G.sub.1 and G.sub.2 act as a single
"fixation point"; that is, for a normal visual system, the two disks
appear as a single, small, flashing green light a long distance away.
Their function is simply to provide the patient with something to look at,
thus keeping their eyes relatively still and focused at infinity, or as
close to infinity as their refractive error allow.
Sources S.sub.2 are yellow LEDs. Light from sources S.sub.2 pass through
lenses L.sub.2, and is reflected from cold mirror CM.sub.1 to the right
eye. Lenses L.sub.2 form images of sources S.sub.1 in the plane of the
patient's pupil, and the light then passes through the pupil and
illuminates one or more of the four quadrants of the retina. If the
patient is looking at source S.sub.1, then the light from sources S.sub.2
will fall respectively on the superior and inferior temporal and superior
and inferior nasal quadrants of his right retina as indicated, for
example, in FIG. 23. The size of source S.sub.2 and the magnification of
its image in the plane of the patient's pupil are such that the image is
much smaller than the smallest pupil diameter. Thus, the amount of light
that falls on the retina from sources S.sub.2 does not change when the
pupil size changes, as it would do under ordinary circumstances.
The lens assembly for lenses L.sub.1 and L.sub.2 is shown in FIG. 33A and
comprises the centrally mounted lens L.sub.1 surrounded by four Fresnel
lenses L.sub.2. These four lenses focus light from each of four LED
sources S.sub.2 on the right pupil and illuminate the four quadrants of
the retina. The lens assembly for lenses L.sub.3 and L.sub.4 is similar to
that shown in FIG. 33A but focus light from sources S.sub.3 and S.sub.4 on
the left pupil.
Considering next the part of the optical system that provides images of the
patient's pupils, reference is made to FIG. 34 which shows part of the
optics for the right eye. It will be understood that this part of the
optics for the left eye is identical and is therefore not shown. Source
S.sub.5 is a small infrared-emitting LED. Infrared light reflected by
mirror M.sub.1 passes through lens L.sub.5 and half of it is reflected
from a beam splitting mirror BS.sub.1. Light reflected from mirror
BS.sub.1 is transmitted through the cold mirror CM.sub.1 (FIG. 33) to the
right eye. Lens L.sub.5 forms an image of source S.sub.5 in the plane of
the patient's pupil (superimposed on the images of sources S.sub.1 and
S.sub.2). The image of source S.sub.5 is also smaller than the smallest
pupil, and the infrared light passes through the pupil and spreads over a
region of the retina.
With continued reference to FIG. 34, some of the infrared light reflected
from the retina emerges back out of the pupil and travels back through
cold mirror CM.sub.1 and beam splitter BS.sub.1. Part of that light is
reflected from beam splitter BS.sub.1 toward lens L.sub.5 and lost, but
the rest is transmitted by beam splitter BS.sub.1 and passes through lens
L.sub.6 (FIG. 33), which lies at its focal distance from the pupil.
Therefore, the infrared image of the pupil, as back lighted by scatter
from the retina, is collimated as it emerges from lens L.sub.6. This light
is reflected from a mirror M.sub.2, part of it is reflected from another
beam splitter BS.sub.3 and passes through lens L.sub.7, which forms an
image of the pupil in its focal plane. An infrared sensitive video CCD
(charge coupled device) camera is placed in that plane and positioned so
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