Ophthalmoscope with uniform illumination

Apparatus for viewing an eye fundus through a contact lens has an illuminating element that illuminates the fundus through the sclera. The illuminating element includes at least one fiber optic bundle with an exit facet for placement contiguous with the sclera, generally through whatever thickness of occular conjunctiva is present. The apparatus also has an optical mask system which masks the image of the fundus portion most intensely illuminated by the fiber optic exit facet to control over-illumination of that fundus portion.

BACKGROUND OF THE INVENTION 
This invention relates to an ophthalmoscope, i.e., an instrument for 
viewing the interior of the eye. More particularly, the invention provides 
a wide-angle ophthalmoscope which achieves more uniformly illuminated 
imaging of the eye fundus than heretofore possible. 
The invention thus provides a wide-angle ophthalmoscope having a superior 
uniformity of image intensity at the ophthalmoscope viewing location, as 
compared to prior devices of this kind. Due to these and other advantages 
set forth below, an ophthalmoscope embodying the invention enables 
superior viewing of the entire retina, and photographing it, in a single 
image with a single placement of the instrument. 
My previous patents and patent applications, noted above, describe 
wide-angle ophthalmoscopes having improved constructions for both 
illumination through the crystalline lens and transillumination through 
the sclera of the patient. With the first type of illumination there is 
often a noticeable diminution of illumination at the posterior pole of the 
fundus as well as the requirement for significant dilation of the 
patient's pupil; with the second there is an intensely bright spot on the 
image corresponding to the fundus portion adjacent the sclera location 
where transillumination occurs. 
Accordingly, it is an object of this invention to provide a wide angle 
fundus-viewing instrument in which the optical intensity of the fundus 
image, as seen from the viewing location, is more uniform than in prior 
devices of this kind. 
A further object is to provide improvements in a transillumination type 
ophthalmoscope that yield such improved image uniformity and that can be 
provided as add-on features to existing ophthalmoscopes of this type. 
It is also an object of this invention to provide a wide-angle ophthalmic 
instrument using illumination applied through the eye sclera and which 
provides an image having relatively uniform brightness. It is a further 
object to provide such an instrument capable of providing such uniform 
image brightness with subjects having eyes of different geometries, i.e. 
different sizes and shapes. 
Another object of the invention is to provide an ophthalmic device of the 
above character which is of relatively simple and low cost construction, 
and which is relatively easy to operate. 
Other objects of the invention will in part be obvious and will in part 
appear hereinafter.

SUMMARY OF THE INVENTION 
The invention stems from the finding that the illumination of a retina 
through the sclera, for ophthalmologic examination, can be made more 
apparently uniform at the instrument output than occurs with reliance only 
on sclera diffusion of light. In the new instrument, optical mask means 
effectively reduce fundus image intensity at over-illuminated locations 
(i.e. the locations corresponding to the exit fact of the light source). 
In the practice of the invention, the transillumination is preferably 
directed through a narrow region of the sclera termed the pars plana. This 
region lies in a generally annular area between the ciliary body and the 
ora cerrata. 
Examination of an eye with transillumination through the pars plana and 
with appropriate optical output masking according to the present invention 
can provide a field of view and an observable field of 160.degree. from 
the nodal point, all of which is imaged with superior apparent uniformity 
of illumination. Hence, this image of the field can be more readily 
examined by an observer and/or photographed, or otherwise recorded, as a 
single scene or frame. Further, the uniform brightness of the image 
enhances the observation of fine structures and other detail. 
A mask system according to the invention has at least one optical mask 
member located in selected optical alignment with the optical axis of the 
ophthalmic device. The mask member reduces the brightness of the fundus 
image at a region of the image corresponding to a location on the fundus 
where applied illumination enters the eye through the sclera. The mask 
member preferably is disk-like and has a selected opacity configuration. 
In one embodiment the mask member is totally opaque with a contoured 
periphery; in another it has regions of different opacity. The mask member 
generally lies in a plane transverse to the optical axis and can be 
reciprocated into and out of the fundus image to provide the desired 
masking. Alternatively, the mask member can be rotated about an axis 
parallel to the optical axis. The mask member also can be adjustably moved 
to match the geometry of the eye being examined, and then either moved as 
above, or maintained stationary, during viewing for examination and/or 
recording. 
The invention accordingly comprises the features of construction, 
combination of elements, and arrangement of parts exemplified in the 
constructions hereinafter set forth, and the several steps effected 
thereby, and the scope of the invention is indicated in the claims. 
DESCRIPTION OF ILLUSTRATED EMBODIMENTS 
FIG. 1 shows a wide-angle ophthalmoscope 10 according to the invention 
operatively disposed contacting a human eye indicated generally at 12. The 
ophthalmoscope includes an optical mask system housing 14 in front of a 
viewing or recording device 16, which can include an observer's eye, a 
camera, or other optical viewing or recording equipment. The 
ophthalmoscope has a contact lens 18 that images the eye fundus outside 
the eye. That is, the contact lens 18 enables an exterior viewer to 
observe up to essentially a 160.degree. solid angle of the eye fundus 
through the pupil 12a and crystalline lens 12b of the eye. 
The ophthalmoscope has a fundus illumination system 22, illustrated in the 
form of bundles 22a and 22b of optical fibers, which directs light from a 
source 24 into the interior of the eyeball through the sclera 12c, and 
whatever thickness of the conjunctiva 12d which is present. The sclera and 
adjacent layers of the eye structure diffuse the light that the lamp 
element 22 projects. Hence, the resultant illumination within the eyeball 
is scattered throughout the fundus. The two bundles 22a and 22b preferably 
are disposed on the horizontal sides of the pupil in the access space 
normally available on an eye, i.e. the placement of one is temporal and of 
the other is nasal. Where desired, of course, one or more bundles can be 
placed elsewhere on the eyeball, with evident related changes in the 
optical mask system discussed below. (The ophthalmoscope can include a 
second lamp element formed by optical fibers disposed in a conical array 
around the contact lens 18, in the manner disclosed in my prior patents 
and patent applications noted above.) 
In view of the foregoing, it should be understood that when in use, the 
ophthalmoscope is centered on the eye 12 and hence the lens 18 is located 
on the cornea 12e optically aligned with the crystalline lens 12b along an 
optical axis 20. Each bundle 22a, 22b of the lamp element 22 is generally 
normal to the eyeball and is disposed at the sclera 12c. Further, each 
bundle is located at the pars plana 12f, which is the annular portion of 
the sclera between the ciliary body 12g and the ora cerrata 12h. As 
previously noted, the optical transmission of the sclera and the adjacent 
layers at the ora cerrata is relatively high in the regions of the 
spectrum that are used, due to the small thickness of optically-absorbing 
material there, as contrasted with adjacent regions. 
The ophthalmoscope contact lens 18, when in contact with an eye cornea as 
illustrated, increases the power of the optical system of the eye being 
examined and brings the image of the fundus from infinity to a finite 
distance in front of the eye. For this purpose, the lens has a 
concavo-convex configuration with generally frusto-conical sides. The lens 
construction may be as described in the above-mentioned U.S. application 
Ser. No. 536,879. 
Each fiber optic bundle 22a, 22b of the lamp element 22, as already noted, 
is configured to be disposed on the eye to illuminate the fundus through 
the sclera at the region of maximum optical transparency, i.e. at the pars 
plana. There preferably are two bundles 22a and 22b as illustrated, one 
located temporally and the other in a nasal location. Each bundle contacts 
the sclera at a spacing generally between ten and seventeen millimeters 
from the axis 20 in order to engage the pars plana. The exact location of 
the bundles against the eyeball for optimum illumination will, of course, 
vary depending on the size of the eyeball being examined. A construction 
in which each bundle has a diameter of five to six millimeters at its 
engagement with the eyeball, and in which the bundle engages the eyeball 
at around fourteen millimeters from the central axis 20, suffices for most 
instances. With this arrangement, light from the two bundles 22a and 22b 
appears as two bright spots on the inner surface of the bulb of the eye, 
and illuminates the posterior segment of the bulb. 
FIG. 1 shows that the resultant aperture of direct illumination (i.e. 
excluding diffusion and scattering) from each bundle 22a and 22b is within 
a solid angle bounded by the rays 26 and 28. This aperture of direct 
illumination typically is a 48.degree. solid angle. However, as noted, 
there is significant diffusion of the illumination from the lamp element 
22 in passing into the interior of the eyeball so that the illumination 
from each bundle is scattered far beyond the region of direct 
illumination. This scattering generally is considered desirable, for it 
enhances illumination over the entire observable field of the fundus. 
Referring to FIG. 2, the lower portion is an illustration of a quadrant of 
the fundus image produced by an ophthalmoscope constructed in accordance 
with the teaching, for example, of the above-mentioned U.S. application 
Ser. No. 536,879. A region 30 at the lateral periphery of the image is 
very bright owing to the positioning of the fiber optic bundles 22a and 
22b adjacent the corresponding fundus portions. That is, the image has a 
region 30 of bright illumination or "flare" at the site of each bundle 22a 
and 22b. According to the present invention, I have found that in each 
region 30 there is typically a complete saturation of the photographic 
film upon which the fundus image is recorded, e.g. when recording device 
16 is a camera. Referring to the upper portion of FIG. 2, it shows a graph 
of illumination intensity as a function of location on a diameter across 
the fundus image shown in the lower portion of FIG. 2. The solid line of 
the graph is representative of the illumination intensity at various 
regions of the fundus and was obtained by measuring degrees of exposure of 
the photographic film at corresponding locations of the fundus image. As 
is evident from FIG. 2, the brightness is substantially uniform from the 
center of the image out to a location, indicated at A, that corresponds to 
the beginning of a region 32 surrounding the bright region 30 of the 
fundus image. In this region 32, as is evident from the graph, the level 
of light illuminating the fundus portion increases with increased 
proximity to region 30. In the region 30, however, measurements from the 
photographic film would indicate a uniform brightness (see the graph 
portion between points B and C), although at a much higher level than the 
uniform brightness at central portions of the fundus, i.e. to the left of 
point A. 
I have realized, however, that this apparent uniformity of illumination in 
the region 30 is actually the result of saturation of exposure of the 
photographic film and that there is a real increase in the level of 
illumination on the fundus in this portion as indicated by the broken line 
segment of the graph in FIG. 2. It is the analysis of these increased 
levels of brightness at peripheral portions of the fundus, as well as an 
implementation of an ophthalmoscope that corrects for this situation, that 
form the basis of the present invention. 
FIG. 3 is an illustration of one ophthalmoscope constructed in accordance 
with the present invention and showing somewhat more detail than FIG. 1. 
Thus, the optical elements are supported within a housing 34 that is 
mounted on a larger housing 37 which encloses an optical mask system. 
Brackets 36 mounted on the housing 37 support the fiber optic bundles 22a 
and 22b at locations somewhat spaced (e.g. one and one-half inches) from 
the bundle end faces that contact the patient's eye. 
In view of my findings summarized above with reference to FIG. 2, I have 
realized the desirability of providing in the ophthalmoscope an optical 
mask system to mask the portions of the optical image which correspond to 
the regions 30 and 32 of FIG. 2 to compensate for the excessive 
illumination of the fundus at the corresponding regions thereof. The mask 
system of FIG. 3 provides this operation in a timed sequence. This optical 
mask system is described with reference to the broken away portion of 
housing 37 in FIG. 3 and with reference to FIGS. 4 and 5. 
The illustrated optical mask arrangement includes a frame 38 formed with 
front and rear frame members 40 and 42. Each frame member has a central 
circular opening 44 that is aligned with the optical axis 20 (see FIG. 1) 
of the ophthalmoscope's optical system and that defines the aperture of 
the image transmitted by the ophthalmoscope to the observer, camera, etc. 
(The opening 44 thus corresponds to a spatially-displaced, full image of 
the fundus, a quadrant of which is illustrated in FIG. 2). The frame 
member 42 forms a rectangular recess 46 within which a pair of mask 
members 48, 48 is slidably supported. 
Each mask member 48 includes a curved lobe 50 directed toward the optical 
axis 20 of the system and having curvature chosen substantially to match 
the curvatures of the regions 30 and 32 illustrated in FIG. 2. Each mask 
member 48 is slidable within the recess 46 between a first position (shown 
in FIG. 5 with broken lines) in which each lobe 50 overlaps the opening 44 
to mask an area substantially equal to the combined areas of regions 30 
and 32 in FIG. 2, and a second position (shown with solid lines) in which 
the lobes 50 are fully retracted so as to not overlap the openings 44 at 
all. Extreme precision in the size and shape of each lobe 50 is not 
essential since any empirical determination of the regions 30 and 32 of 
FIG. 2 includes an inherent degree of imprecision and, also, since those 
regions, are, in part, determined by the physical characteristics of the 
eyes of individual patients. In a presently preferred embodiment 
illustrated, each lobe 50 is a portion of a circle having a radius of 0.71 
inch and each lobe projects from the adjacent straight edge 51 of the mask 
member 48 by a distance of 0.39 inch. 
The movement of the mask members 48 between their respective two positions 
is produced by a precision stepping motor 52 that drives a rotary cam 54, 
which, in turn, drives a linkage connected to the mask members 48. The cam 
54 is a rotary cam wheel or disk coaxial with the drive shaft of stepping 
motor 52 and includes a cam groove 58 that receives a pin 56 secured to 
the linkage. As discussed below, according to the present invention it has 
been realized that a very rapid movement of the mask lobes 50 to mask the 
region 30 illustrated in FIG. 2 is desirable, and a relatively slower 
advance of the lobe 50 into the region 32, and any subsequent retraction 
therefrom, is also desirable. In the illustrated embodiment, the cam 54 
has a groove 58 shaped to achieve this type of motion of the mask members. 
In that embodiment the circumferential extent of the groove is 180.degree. 
and its total radial extent is 0.354 inch. The groove is cut, however, 
such that one-half of that radial motion (i.e. 0.177 inch) occurs in the 
first 18.degree. of rotation of the cam 54 (i.e. the first one-tenth of 
the total time of rotation) and the remaining 0.177 inch of radial 
movement occurs in the remaining 162.degree. of rotation. It may be 
preferable to start operation with the mask lobes fully projected, i.e. in 
the aforementioned first position, in which case the cycle starts with 
162.degree. of cam rotation retracting the lobe slowly, followed by rapid 
retraction during the next 18.degree. of rotation, rapid initial return 
and slow final return to the initial position. 
The pin 56 that engages the groove in the cam 54 is a projection of a pin 
56 securing a linkage arm 60 to the mask member 48 closest to the cam. 
Referring in particular to FIG. 5, this construction causes the 
right-to-left and left-to-right movement of the mask member 48 on the 
right hand side of the frame 38, but in a non-linear manner as desired. 
The linkage arm 60 is pivotally connected to a lever arm 62 itself 
pivotally connected, as at 64, to the left side mask member 48. A center 
pivot pin 66 for the lever arm 62 is fixed to the frame member 42 and 
causes a lateral movement of a pivot point 68 (that defines the connection 
between the linkage arm 60 and the lever arm 62) to be translated into an 
opposite lateral movement of the pivot point 64, and thus of the left side 
mask 48. With this arrangement, the two mask lobes 50 can be 
simultaneously driven into a masking relationship with respect to the 
openings 44 (as shown with broken lines in FIG. 5), and simultaneously 
retracted to a non-masking position. 
Turning now to a discussion of the light source (shown schematically in 
FIG. 3 with reference number 24), it will be appreciated by those skilled 
in the art, from the discussion in the above-mentioned U.S. application 
Ser. No. 536,879, that, when transillumination through the sclera is used, 
two entry points of light (i.e. temporal and nasal) are preferably 
employed to assure substantial uniformity of illumination over a major 
portion of the fundus to be viewed. It is for this reason that there are 
two bundles 22a and 22b of fiber optics illustrated in FIGS. 1 and 3. The 
bundles 22a and 22b, of course, simply transmit light received at an input 
end to an exit facet placed adjacent the sclera. Naturally there are a 
variety of ways of providing light input to those bundles. For example, 
independent light sources can be employed for directing an intense beam of 
light onto the input end of each bundle; or a single light source can be 
directed upon the input end of a large collection of optical fibers, which 
is then separated into the two bundles 22a and 22b; etc. 
Another alternative will be described with reference to FIGS. 6, 7A and 7B. 
This illustrated arrangement is particularly suitable for adapting the 
features of the present invention to existing ophthalmoscopes (such as 
those constructed in accordance with the cross-referenced patent 
applications mentioned above) which have but a single light source with a 
collimated output of limited diameter. 
The general arrangement illustrated in FIGS. 6, 7A and 7B is to have end 
pieces 70a, 70b of the fiber optic bundles 22a, 22b supported in a shuttle 
72 that is slidable, relative to the single light source, in a frame 74. 
Any conventional stop arrangement can be provided for the shuttle to 
define two shuttle positions. In each of those positions, one of the end 
pieces 70a, 70b is aligned with an opening 76 that admits light from the 
ultimate light source. The shuttle is spring loaded toward one of those 
two positions, and can be driven, against the influence of the biasing 
spring, by a solenoid 78 to the other of those positions. A microswitch 
80, mounted on the frame 74, is positioned to be closed by the shuttle 
only when in the shuttle position defined by the activated solenoid 78. 
While this arrangement requires sequential separate illuminations of the 
eye fundus employing the bundles 22a and 22b, it is desirable as being 
compatible with existing ophthalmoscopes. In terms of viewing ease, the 
sequential illuminations are inconsequential when, as is common, the 
ophthalmoscope is employed in conjunction with a camera to photograph an 
image of the fundus. With the camera shutter open the entire time, the two 
brief illuminations supplied by the bundles 22a and 22b are essentially 
two "flashes" of a camera flash system, operating while the camera shutter 
is open, and illuminating a motionless subject in an otherwise dark 
environment. 
Because, as mentioned above, it is desirable to move the masks through a 
full cycle, e.g. from a nonobscuring position to a fully obscuring 
position and back again during each illumination, it will be appreciated 
that with the lighting arrangement just described two cycles of the 
optical mask system are preferred for each full observation, photograph, 
etc. of the fundus. The logic diagram of FIG. 8 and the timing diagram of 
FIG. 9 illustrate one preferred system for achieving the double 
illumination, the double masking, and the appropriate timing of all steps 
in the full sequence of use of the ophthalmoscope. 
As described in the previous patent applications referenced above, the 
ophthalmoscope operator initially positions the contact lens 18 and the 
fiber optic bundles 22a and 22b in contact with the patient's eye, as 
illustrated in FIG. 1. The sequence of operation of the instrument, with a 
camera supported and positioned to receive light transmitted through the 
openings 44 shown in FIG. 5, may be described with reference to FIGS. 8 
and 9. Preferably the sequence of operation is initiated with a foot 
switch 82 that can be depressed by the operator. The closing of the switch 
82 is the initial input to a control logic and power supply unit 84 which, 
as will be appreciated by those skilled in logic design, can be 
conventionally constructed to accomplish the functions to be described. 
Major outputs from the unit 84 are signals appearing on output lines 86, 
88 and 90 that are delivered to three solenoid drivers, indicated 
schematically at 92. The solenoid drivers are operative, upon receiving a 
corresponding input signal, to deliver an output signal on lines 94, 96 
and 98 for driving, respectively, camera solenoid 100, light source filter 
solenoid 102, and shuttle solenoid 104. As is evident from FIG. 9, the 
initial action of the unit 84, upon depression of the foot switch 82, is 
to produce output signals that activate the camera solenoid 100 and the 
filter solenoid 102. The camera solenoid is connected to open the shutter 
of the camera 106. As is indicated by lead 108, a signal responsive to the 
shutter-open condition of the camera 106 is transmitted to the unit 84. 
This is also indicated in FIG. 9 by the signal in the "camera output" 
sequence. 
Simultaneous with the opening of the camera shutter, the light source 
filter solenoid 102 drives a filter 110 from the optical path between the 
ultimate light source 112 and the shuttle 72. The removal of the filter 
110 from the light path causes a more intense beam of light to be 
transmitted through the bundle 22a or 22b for illuminating the fundus of 
the patient. Because the filter 110 is removed from the light path for 
short periods of time (i.e. fractions of a second), the action of the 
filter 110 is analogous to that of a conventional "flash unit" for a 
conventional camera. 
Following the actuation of the camera and filter solenoids 100 and 102, the 
camera output 108 causes the unit 84 to generate a sequence of twelve 
uniform pulses delivered on output line 114 for driving the stepping motor 
52 twelve steps in a forward direction. After twelve such pulses, the 
pulse train continues, but with pulses causing the motor to step in the 
reverse direction for twelve steps. As is evident from FIG. 9, the pulse 
train is interrupted after the second twelve pulses. 
This dual series of twelve motor stepping pulses causes the cam and linkage 
arrangement described above in relation with FIGS. 3, 4 and 5 to drive the 
mask elements 48 from a position in which the lobes 50 are 
non-interfering, to the fully masking position, and back to the original 
position. Simultaneous with the cessation of the last pulse of the train 
of twenty-four pulses, the unit 84 causes deactivation of the filter 
solenoid 102 and the attendant re-insertion of the filter 110 into the 
light path, thereby avoiding exposure of the photographic film from the 
intense light at a time when the masking system is not in operation. Also 
upon cessation of the twenty-fourth pulse, the unit 84 activates the 
shuttle solenoid 104 causing the shuttle 72 to shift from its first to its 
second position, so that the fiber optic bundle 22b is now aligned with 
the light source 112. FIG. 9 illustrates a slight delay in further action 
owing to the time delay in the mechanical movement of the shuttle. 
When the shuttle has reached its second position, however, the shuttle 
position detector 80 (i.e. the microswitch) delivers an output signal on 
lead 116, which is indicated schematically in FIG. 9, to the unit 84. This 
shuttle position detector output causes the unit 84 to initiate a second 
sequence of twelve forward motor stepping pulses, followed by twelve 
reverse motor stepping pulses, all applied to line 114 leading to the 
stepping motor 52. Silmultaneous with the initiation of the first pulse of 
that second sequence, a signal is generated to cause the filter solenoid 
102 to once again remove the filter 110 from the light path. Termination 
of that signal to the solenoid 102, and consequent re-insertion of the 
filter 110 into the light path, occurs with the final pulse of the 
twenty-four pulse series delivered to the stepping motor 52. The filter 
110 is therefore removed from the light path only during the sequence of 
twenty-four pulses which occur during the second exposure of the fundus 
(i.e. the exposure produced by light delivered through bundle 22b), just 
as it was with the first exposure. Termination of the second twenty-four 
pulse train also causes deactivation of the camera solenoid 100 (thereby 
closing the camera shutter) and deactivation of the filter solenoid 102 
and shuttle solenoid 104. Deactivation of these latter solenoids permits 
the filter 110 and the shuttle 80 to return to their original positions, 
typically under the influence of biasing springs. 
As is evident from the preceding discussion, it is important that the 
stepping motor 52 and the attached cam member 54 be properly "zeroed" 
prior to the commencement of an operating sequence of the ophthalmoscope. 
As a precaution, therefore, a sensor 117 (e.g. a photocell positioned to 
sense the "zero" position of the cam) can be employed to determine whether 
or not the stepping motor 52 is at its "zero" orientation. The signal 
produced by sensor 117 is delivered by a lead 118 to the unit 84. In one 
preferred arrangement, the unit 84 has an indicator (e.g. a light) on an 
exposed panel to indicate when the stepping motor is in the zero 
orientation and when it is removed from that orientation. An associated 
manually-operated switch can be provided to deliver an uncounted sequence 
of stepping pulses to the motor 52 when the switch actuator is depressed. 
With this arrangement, of course, it is a simple matter for the operator 
of the equipment to zero the stepping motor, prior to initiation of a 
cycle of operation of the equipment, by simply depressing the switch 
actuator on the unit 84 until the indicator is in the appropriate 
condition (e.g. light on or off as the case may be). 
It will be understood by those skilled in the art that the sequence of 
operation of the ophthalmoscope, and an attached interacting camera, is 
typically quite brief. For example, the total exposure time (i.e. the four 
twelve-pulse sequences of stepping motor pulses) will typically be no more 
than one-eighth of a second in duration. As is clear from FIG. 9, with 
such an exposure time, the total sequence of operation will be only 
slightly more than an eighth of a second. As will be appreciated by those 
skilled in the art, the exposure time can be easily adjusted in various 
ways. One convenient way is to employ a clock (from which the stepping 
motor pulse sequences are delivered) that has a variable period. 
As will also be apparent to those skilled in the art, the shuttle 
arrangement and the second full sequence of stepping motor operation 
evident from FIG. 9 could be eliminated by providing for the input of 
light simultaneously to both fiber optic bundles 22a and 22b. With both 
bundles illuminating the eye simultaneously, only a single cycle of mask 
reciprocation is required, and the fundus receives in one-half the time 
the same level of illumination it receives with the illustrated embodiment 
operating according to FIG. 9. As mentioned above, however, the light 
sources tend to be quite expensive so that the cost of the shuttle 
arrangement, and the additional control logic required, usually will be 
less than the cost of a second light source. Additionally, certain 
commercially available ophthalmoscopes are constructed with a single light 
source and, thus, the described arrangement can be provided in the form of 
an attachment to be used with existing ophthalmoscopes. 
For clarity of description the invention is described in terms of an 
ophthalmoscope. As noted above, this term is used herein with reference to 
any device for examining (including recording) an eye fundus. Hence the 
device 10 illustrated and described herein can be part of a fundus camera, 
or of another instrument which is used for viewing, recording or otherwise 
examining an eye fundus. 
FIGS. 10 and 11 show an ophthalmoscope 120 according to another embodiment 
of the invention which uses rotating masks, rather than reciprocating 
masks as hereinabove. The rotating mask motion can avoid the need to 
synchronize the masking with other operations. The ophthalmoscope 120 thus 
is simple to operate and relatively low in cost, yet provides a wide-angle 
fundus image that is essentially free of bright spots or other significant 
nonuniformities in apparent illumination due to light applied through the 
sclera. 
The illustrated rotating mask ophthalmoscope 120 is largely similar to the 
FIG. 1 ophthalmoscope 10 except for a mask system 122. Accordingly, 
elements of the ophthalmoscope 120 corresponding to those in FIGS. 1 
through 9 bear the same reference numerals except with a superscript 
prime, for example the ophthalmoscope 120 employs a contact lens 18'. The 
mask system 122 of the ophthalmoscope 120 employs a pair of disk-like and 
typically identical masks 124, 126 rotatably mounted on a support casing 
128. The casing 128 typically is mounted on a base or stand (not shown) in 
front of the face of the subject with the axis 20' of the ophthalmoscope 
aligned with the eye 12' being examined. The casing carries the housing 
34' of the contact lens 18' and other optical elements, and mounts 
brackets 36', 36' which support fiber optic bundles 22a' and 22b' of a 
fundus illuminating system 22'. A circular opening 130 in the casing is in 
optical alignment along the axis 20' with the optical elements within the 
housing 34'; the opening defines the aperture of the image which the 
ophthalmoscope 120 projects to the camera 16' or other recording or 
observation device. 
Each mask 124, 126 is mounted on the casing for rotation about a respective 
rotation axis; the rotation axes are parallel to the optical axis 20' of 
the instrument. The masks are located substantially symmetrically on 
either side of the aperture opening 130, and each projects into the 
opening over the portion of the projected fundus image which corresponds 
to the excessively illuminated regions 30 and 32 of FIG. 2. However, each 
mask 124, 126, which like the reciprocating masks of the FIG. 1 
ophthalmoscope 10 is substantially optically opaque, has a selected 
circumferential contour. The configuration of this contour is such that, 
when the mask rotates, it passes to the viewer selected fractions of the 
image light incident on it. The level of the image light which the 
rotating masks thus transmit has essentially the same intensity as at the 
center of the image, i.e. as the uniform portion of the FIG. 2 graph 
between the Y-axis and the point A. 
The rotating mask system does not require synchronization with the 
illuminating system 22' or with whatever image recording is used at the 
viewing point of camera 16'. In typical operation, the motor drive which 
rotates the masks runs continuously, the illuminating system 22' provides 
continuous illumination of the eye fundus being examined, and the camera 
or other image recording instrument is operated independent from the 
illumination and from the masks to provide whatever photographs or other 
recordings are desired of the fundus image. The reason for this time 
independence of the rotating mask system 122 is that the illustrated 
rotating masks selectively block image illumination several times during 
the interval of one photographic exposure or other recording interval. 
This relatively high speed masking is readily obtained by scalloping each 
mask with a pattern which repeats around the mask circumference and by 
rotating each mask at a sufficiently high rate of speed relative to the 
image recording time. 
The time independence with which the ophthalmoscope 120 thus operates 
significantly reduces its cost relative to a system which requires 
synchronized operation, and simplifies construction and operation. Another 
advantage of the rotating system is that it operates quietly and smoothly 
with minimal vibration. This further enhances the quality of the images 
which can be recorded with the instrument. 
Each rotating mask in the ophthalmoscope 120 effects the brightness of the 
image at the portions which correspond to the regions 30 and 32 of FIG. 2. 
Accordingly, each disk-like mask has a circular outer periphery 124a, 
126a, along which the radially-outermost points lie, having a radius 
corresponding closely to the outer curvature of the FIG. 2 portion 32, 
i.e. the curvature of the portion edge adjacent point A. (In one 
embodiment of the invention, each mask as in FIG. 11 has a maximum outer 
diameter of twenty-two millimeters.) 
Further, each mask can be mounted on the support casing 128 to project into 
the aperture opening 130 to locate this circular periphery 124a, 126a 
generally in register with this edge of the portion 32. The illustrated 
embodiment, however, mounts each mask on a separate slide block 125, 127 
which is movably adjustable relative to the casing 128 in the manner 
detailed hereinafter. This enables each mask 124, 126 to be adjustably 
positioned for optimal masking of the eye being studied, e.g. for eyes of 
different geometries. 
The scalloping of each rotating mask corresponds approximately to the 
change in image brightness as a function of radial distance, as the graph 
in FIG. 2 plots. The opaque area of the mask accordingly progressively 
increases with decreasing radius on the disk-like shape of the mask, as 
FIG. 11 shows. It has further been found that the mask in some instances 
imposes perceptible shadows on the ophthalmoscope image when, for example, 
many crests of the scalloped edge are at the same radial distance, and 
similarly when many valleys or troughs are at the same radial distance. To 
avoid this and other optical "imprints" of the rotating mask, the mask 
configuration which FIG. 11 illustrates has the several peaks and valleys, 
and in general has an overall distribution of the scalloped edge, at 
different radial distances from the center of the circular outer periphery 
124a, 126a. It further is considered preferable that the corners of the 
scalloped edge be rounded, i.e. to have gradual transitions. 
The scalloped mask configuration which FIG. 11 shows illustrates one 
preferred embodiment for attaining the foregoing objectives. The 
configuration has a pattern of narrow-wide-narrow scallops which repeats 
every 90.degree. around the mask circumference. Superimposed on this are 
two equally-spaced narrower and significantly deeper scallops. FIG. 12 
shows another mask configuration, the basic contour of which repeats every 
45.degree. so that the pattern is repeated eight times around the mask 
periphery. Superimposed on this repeating pattern are four equally-spaced 
deeper troughs, two opposite ones of which are deeper than the others. 
Other mask configurations can be used, the invention is not limited to 
those which FIGS. 11 and 12 show. 
FIG. 13 shows one such alternative; that mask has a contour formed by two 
helically or spirally increasing semicircular segments. The narrow width 
of one segment is adjacent the wide end of the other, and a slot apertures 
the juncture. The illustrated rotating masks thus provide narrow slit-like 
apertures at locations corresponding to the bright fundus regions 30 (FIG. 
2) and significantly more and radially-increasing aperture area at 
locations corresponding to the transition regions 32. 
With further reference to FIGS. 10 and 11, the support casing 128 of the 
illustrated ophthalmoscope 120 is constructed with a plate 132 that mounts 
the mask system 122 as well as the lens housing 34' and the brackets 36', 
36' that carry the fiber optic bundles 22a', 22b'. The plate is apertured 
to form the opening 130 and is recessed with channels 134, 136 that 
slidably seat the slide blocks 125, 127. Each channel extends laterally 
(i.e. horizontally, from side to side in FIGS. 10 and 11) along the plate 
from one edge toward the opening 130 and has upper and lower slide rails 
138 extending therealong. Each block 125, 127 has slide tracks 140 along 
the upper and lower sides and slidably seats within one channel with the 
channel rails slidably engaged with the tracks. The block is thus slidable 
along the channel and the rail-track engagement holds the block securely 
seated in the channel. (Alternative to the rail and track structure, one 
can, for example, use a cover plate overlying and fastened to plate 132 to 
secure the slide blocks in the channels). 
Each slide block 125, 127 carries one mask 124, 126 and carries a drive 
motor 142, 144 that rotates the mask by means of a drive belt 146, 148. 
The masks are fixed on shafts 150, 152 that are rotatably mounted, as with 
bearings, to the blocks 125, 127 adjacent the ends thereof proximate to 
the opening 130. The shafts, which are parallel to the optical axis 20' to 
dispose the masks in a common plane transverse to this axis, carry sheaves 
154, 156. The motors 142, 144 are mounted on the blocks at locations 
spaced further from the opening 130; they extend outward from the casing 
128 through slots which aperture the plate 132 along the channels 134, 
136. The shaft of each motor extends through the motor-mounting slide 
block and carries a drive sheave 158, 159 which the belt 146, 148 couples 
to the mask sheave on that block. With this construction, sliding 
adjustment of a block 125, 127 along a channel adjusts the amount of mask 
projection into the opening 130, but does not change the coupling of the 
mask to its drive motor. 
As FIGS. 10 and 11 also show, the casing plate 132 pivotally mounts 
upstanding levers 158, 160 which are pinned at slots 162, 164 to the slide 
blocks 125, 127 respectively. Pivotal movement of a lever by the operator 
slides the corresponding block, along the channel in which it is mounted, 
to effect this positioning adjustment of a mask. (Means not shown can be 
provided to secure the slide blocks after adjustment.) It will be seen 
that the levers are well spaced from the ophthalmoscope axis 20' and hence 
are readily accessible to the operator. 
As indicated above, the speed of rotation of each motor 142, 144 preferably 
is selected so that each mask 124, 126 obscures and alternatively passes 
image illumination several times during the imaging interval, e.g. during 
the exposure time for photographing the fundus image. By way of 
illustrative example, an embodiment with the illustrated construction 
rotates each mask through at least two full revolutions during each 
photographic exposure of the fundus image. Where desired, the motor speed 
can be adjustable to enable the operator to change the speed of mask 
rotation. 
As FIG. 10 also shows, the illustrated optical source 24' has a single lamp 
and two lens systems which direct illumination onto the entry facets of 
the fiber optic bundles 22a' and 22b'. 
During operation of the ophthalmoscope 120, the optical source 24' and the 
motors are turned on, and the slide blocks adjusted for optimal masking of 
the eye being examined. The resultant fundus image can then be studied or 
recorded, e.g. photographed, as desired. So long as the masks rotate 
sufficiently fast so as not to undesirably shadow the image, there is no 
need to synchronize the mask rotation or the optical source operation with 
the image viewing and recording. 
Although described with reference to an ophthalmoscope 120 which provides 
for adjustable lateral positioning of the masks, a rotating mask system as 
FIGS. 10-13 illustrate can be practiced with fixed axes of mask rotation. 
The masking will match some eyes, and will also provide significant, 
nearly equal, improvements in observed image illumination for the eyes of 
other subjects. 
The invention can also be practiced with an ophthalmoscope 160, shown in 
FIGS. 14 and 15, which has optical masks 162, 164 that are adjustable, but 
which can remain stationary during the fundus examination and image 
recording. Further, the masks 162, 164 in this instrument have selected 
graduated optical transmission, as provided for example by a 
selectively-exposed photographic negative. The ophthalmoscope 160 is 
constructed in large part like the opthalmoscope 120 of FIGS. 10 and 11, 
except with different masks and a different mask-moving mechanism. 
Accordingly, elements of the ophthalmoscope 160 which are common to FIGS. 
10 and 11 bear the same reference numerals in FIGS. 14 and 15. 
Instead of carrying a motor as in FIGS. 10 and 11, each slide block 124, 
125 of the FIG. 14 ophthalmoscope 160 carries a knob 166, 168. The knob is 
mounted for rotation with a shaft 170, 172 journaled to the slide block 
125, 127, respectively. The shaft extends beyond the block to mount the 
respective drive sheave 158, 159. The knobs 166 and 168 serve both to 
adjustably position the mask-carrying slide blocks 125 and 127 and to 
rotationally adjust the masks. However, the slide blocks can, when 
desired, be adjustably positioned by means of pivoting levers 158 and 160 
as shown in FIGS. 10 and 11, as well as with other adjustment mechanisms. 
As shown in FIG. 15 and with greater detail in FIG. 16 for the mask 162, 
each mask 162, 164 has a central region 174 that is substantially 
uniformly dense at an optical density of three, and which is bounded by a 
transition region 178. This region has an opacity that decreases from 
density three to zero with increasing radius from the central point 178 
about which the mask is rotated on the corresponding shaft 150, 152. The 
periphery of the mask is essentially transparent. The contours of the mask 
regions 174 and 176 correspond respectively with the contours of the 
overly-bright fundus image regions 30, 32 of FIG. 2. The radial change in 
opacity in mask region 176 corresponds inversely to the change in 
brightness which the curve in FIG. 2 shows, particularly between points A 
and B. Moreover, different circumferential portions of the graduated mask 
correspond to these features as found with different eyes, e.g. eyes of 
different geometry and of different optical transmission for illumination 
applied at the sclera. 
For this purpose, the graduated mask shown in FIGS. 15 and 16 has four 
circumferentially-extending sections a, b, c and d. In each section the 
central region 176 is bounded by a different curvature, typically a 
circular curvature of different radius from the other sections. The 
transition region is of generally uniform width around the central region. 
The mask thus has a generally eliptical, egg-shaped contour of the central 
region 176, as well as of the transition region 178. 
With this construction and arrangement of each mask, the operator of the 
ophthalmoscope 160 can adjust the mask in and out relative to the 
ophthalmoscope opening 130 (i.e. laterally in FIGS. 14 and 15), and 
rotationally adjust the mask, to match the mask closely with the localized 
increased brightness due to illumination at the sclera for the particular 
eye being examined. The graduated mask preferably is located out of the 
focal plane of the observer/recorder of the fundus image in order to 
diminish the appearance of a shadow of the mask. 
FIG. 17 shows a graduated mask 180 having a continuously changing curvature 
such that it can more optimally mask different eyes. The mask is adjusted 
by rotation and by lateral motion, and remains stationary during fundus 
examination, as described with reference to FIGS. 14-16. The mask 180 has 
a central region 182 of uniform optical density three which is bounded by 
a helical curve. A transition region 184 of radially-decreasing opacity 
from density three to zero bounds the central region and is again of 
uniform width; hence it follows a helical path. Further, the mask 
preferably is rotated about an off-center point 186 and on a rotation axis 
such that the points (m) and (n) at which the mask intersects the 
ophthalmoscope opening 130 remain substantially symmetrically located 
relative to the horizontal diameter of the circular opening as the mask is 
rotated. This arrangement is desired to maintain the area of the mask 
which overlaps the circle substantially equally-divided about the 
horizontal diameter of the opening 130. That is, the projecting portion of 
the mask 180 remains essentially centered on the horizontal diameter of 
this circular opening, as desired. 
The masks of FIGS. 16 and 17, like those suitable for use in the 
ophthalmoscopes of FIGS. 1 and 10, are thin, flat disks. However, rather 
than being uniformly opaque, as is the case for the masks of FIGS. 1 and 
10, the semi-transparent masks of FIGS. 16 and 17 have a graduated opacity 
as described; selectively exposed and developed photographic negative can 
provide the desired ranges of opaqueness. 
The invention thus provides a masking system that produces essentially 
uniform brightness in the image of an eye fundus illuminated through the 
sclera. The masking system can be used to advantage both in fundus 
photography or other recordation, as well as in simple ophthalmic 
observations. 
It will thus be seen that the objects set forth above, among those made 
apparent from the peceding description, are efficiently attained. Since 
certain changes may be made in the above construction without departing 
from the scope of the invention, it is intended that all matter contained 
in the above description or shown in the accompanying drawings be 
interpreted as illustrative and not in a limiting sense. 
It is also to be understood that the following claims are intended to cover 
all the generic and specific features of the invention herein described, 
and all statements of the scope of the invention, which, as a matter of 
language, might be said to fall therebetween.