CA1312230C - Photo-deviometer - Google Patents

Abstract

Photo-Deviometer Abstract Disclosed is a photo-deviometer by which accurate and reproducible measurements and photographs are obtained on a wide range of patients of all ages and ethnic background affected by strabismus.

Description

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Phot Q eviometer Field of the Inve~
The present invention is in the ~ield of strabismus for deviometry and photography.
Backaround of_~he Invention Strabismus is an e2traocular muscle disorder resulting in:misalignment of the eyes. It is reported to affect one t~ three percent of the population in the United States (Helveston E~, "The Incidenc~ of ~mblyopia ex Anopsia in Young Adult Males in Minnesota in 1963" ~m~
J- Oph~hal., 60:75-77, 1965; Florm McNeomaier, RW, ~Prevalence of Amblyopia" Public Health ~ep. 8:29:34, 1966). Ophthalmic photographers are often a~ked to document this ocular misalignment both b~fora and after strabismus surgery. The resulting photographs are then used for comparative studies, case presentations, teaching tools, and publications. It is thus important to generate accurate and reproducible photographs on a wide range of patients of all ages and e~hnic backgrounds ~ffected with strabismus. The present invention is directed to a gaze fi~ation device for strabismus photography (nine gaze -2~ 2 2 3 ~

cardinal photography) and deviometry which is referred to herein as the photo-deviometer.
Deviometry, the measurement of strabismu~ in the cardinal positions of qaze, was initially deYeloped as a 5 met~od of documenting incomitance of strabismus, particularly in the case of a paretic vertically acting muscle.
The first deviometer, the Owen's deviometer (3), was designed in 1947 and consisted of a rotating arm (15.4 10 cm long) with a near fixation light set at 5.5 cm away from the patient. Ths angle of fization remained at 25 degrees from the primary position throughout the dif~erent positions of gaze. The deviation was then determined ob~ectively by using the prism and cover test. The major 15 disadvantaga of the Owen's deviometer was the lack of an accommodative fi~ation target. Since adequate control of accommodation was not possible, inaccurate and variable measurements resulted.
Methods other than deviometry for documenting 20 gaze incomitance have been described. The most common clinical method is to passively turn the patient's head so that the eyes are in the intended positions o gaze. The problem with this technique is the difficulty in obtaining consistency of head position. A slight head tilt, chin elevation or depression can easily be introduced. This method is rarely satisfactory because of lnaccuracy and inconsistent measurements.
An ideal deviometer would allow measureMents in the cardinal positions of gaze while the patient's head remains stationary. Also, it would be hi~hly advantageous to have a central f i~ation target or images and accommodative fi2ation target or images set for deviometry or measurements and fixation targets or images set for extraocular muscle dysfunction, such as 25 and 34, and the position of the recording devices, for e~ample, a 35 13~2230 1 mm SLR camera or a video camera. Such a photo-deviometer fulfills and meets all of these requirements a~d allows accurate and reproducible pre and post treatment measurements and/or photographs.
5 PriQr Art A preliminar~ search was made in the TJ . S . Patent O~fice for the subject matter hereof and the following patents are considered to be the most pertinent developed in this search.
0 U.S. Patent No. 2,132,520 discloses a device for photographing the human eye which includes a card 72 which is read by the subject. The card 72 is located beyond the camera lens 42.
U.S. Patent No. 2,229,721 discloses a camera and appa'ratus ~or photographing the human e~e which includes a Yertical board 18 providing or mounting matter to be viewed by the subject. The board 18 is mounted above the camera casing 10. A "bite bar" 20 is used to immobilize the subject.
U.S. Patent No. 2,257,331 discloses a fundus camera which has no associated target means for directing eye movement.
U.S. Patent No. 2,288,21~ as related to the subject matter of this application is essentially the same as that of U.S. Patent No. 2,132,520.
U.S. Patent No. 2,288,430 discloses an apparatus for scanning and recording eye movement. Photo-~lectric cells are used for receiving a re~lected image from light projacted on to a subject's cornea. The subject views material on a wall mounted on top of the apparatus.
U.S. Patent No. 3,944,342 disclose~ a slit lamp and a camera for a binocular microscope.
U.S. Patent No~ 4,5d4,129 discloses a camera-slit-lamp combination for routine eye sxaminations.

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1 The ollowing patents were developed in the search but are considered to be o~ secondary importance:
U.S. Patent Nos. 2,724,305î 3,467,466; 3,583,794;
3,724,932; 3,827,789; and 4,146,311.
5 None of the prior art developed in ~he search recogniæes or solves the problems set forth above; for example (1) "lack of accommodative value" in the prior art deviometers; (2) the failuxe to produce different and easily identif~able images at each fi~ation target; and 0 (3) the realization that over action and under action of oblique muscles are not always apparent at 25 fixation.
The prior art devices do not provide (4) both inner row and outer row fixation pictures for deviometry and e~traocular muscle dysfunction measurements; (5) structure to accommodate patients with ptotic eyslids; (6) a central fi~ation device in the camera; modified camera optics;
modified controls/activator for the camera mirror; and patient's centering means by which accurate and reproducible pre and post treatment measurements and/or 20 photographs can be obtained.
Summ~ry of the Invention The present invention is directed to such a photo-deviometer which overcomes the problems of the prior art devices and provides a device which pro~ides accurate and reproducible photographs on a wide ran~e of patients of all ages and ethnic backgrounds af~ected wi~h strabismus.
Advantageously, the present invention allows measurements in the cardinal position of gaze wh;le the patient's head remains stationary, provides an accommodative fixation target, th~ angle o which in the position of the recording device relative to the patient are standardized by which accurate and reproducible pre and post treatment measurements and/or photographs are obtained.

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The photo-deviometer includes a support structure, a deviometer disk mounted on the structure provid~d with a central fi~ation opening, and includes an inner row and an outer row o~ fi~ation images for 5 deviometry and e~traocular muscle dy~unction measurements. ~n electric selector and illuminating means is provided for selectively illuminating the fixation images. A recording device, such as a 35 mm camera, is mounted on the support structure and its lens is aligned lO with the center of the deviometer disk. An adjustable headrest for fixing a patient's head is mounted on the support structure on the other side of the deviometer dis~. The recording device, central fixation opening, and the patient's eyes, when the headrest is in adjusted 15 positiQn~ provides central fi~ation with respect to the recording plane.
Preferably, there are eight inner and eight outer ~i~ation images. The inner and outer fixation images are disposed at 12:00, 1:30, 3:00, 4:30, 6:00, 7:30, 9:00, and l0:30 o'clock positions.
The inner row of ~ixation images is set for deviometry measurements, and the out~r row of fi~ation images is set at a greater angle for the recording on film of the e~traocular muscle dysfunction.
Preferably, the recording device is a 35 mm camera provided with a ring flash mounted directly on its lens.
Accordingly, it is an object of the present invention to provide a photo-deviometer by which accurate and reproducible pre and post treatment measurements and/or photographs can be obtained.
A further object of the prssent invention is the provision of a photo-deviometer provided with an accommodative fixation target.

-G- 13122~0 A ~urther objec~ of the present invention is the provision of a photo-deviorneter which provides diffarent and easily identifiable irnages at a plurality of fi~ation targets.
It is a further object o~ the present invention to provide a photo-deviometer accommodates over action and under action of oblique muscles not always apparent at normal dev;ometry angIes, ~or example, 253.
It is a ~urther object o the present invention 0 to provide a photo-deviometer provided with both an inner row and an outer row fixation images for extraocular muscle dysfunction measurements and the photographic documentation of the extraocular muscle dysfunction.
A still further object of the present invention is the provision of a photo-deviometer which accommodates patients with ptotic eyelids.
It is a further object of the present invention to provide a photo-deviometer including a support structure, a deviometer disk mounted on the structure and 20 provided with a central fixation opening, and an inner row and an outer row fi~ation images for devismetry and extraocular dysfunction measurements, electronic selectric illuminating means effective to selectively illuminate the fixation images, a reco~ding device mounted on the support structure on one side of the deviometer disk, and an adjustable headrest for fixing a patient's head on the other side o~ the deviometer disk so that the patient's eyes, when the head rests is in an adjusted posit;on, is in central fixation with respect to the plane of the recording device through the center of the opening in the deviometry disk.
It is a further object of the present invention to provide such a photo-deviometer device in which there are eight inner and eight outer fixation images, the inner and outer fi~ation being located at 12:00, 1:30, 3:00, 1 4:30, 6:00, 7:30, 9:00, and 10:30 o'clock positions.
It iS a further object of the present invention to provide such a photo-deviometer in which the inner row of fixation images is set for deviometry measurements and 5 the outer row of ~i~ation images is set at a greater angle for extraocular muscle dysfunction in an up and down gaze of the patient.
A still further object of the present invention is the provision of such a photo-deviometer, in which the 10 inner row o~ fixation images is set at 25, and ~he outer row of fixation images is set at 34~.
It is a ~urther object of the present invention to provide such a photo-deviometer in which the recording device is a 35 mm camera provided with a ring 1ash 15 mounted directly on its lens.
Other and further objects, features, and advantages appear throughout and are in~erent in the photo-d~viometer.
Brief D~$c~iptiQn of ~h~_Drawing$
Figure l is a perspective view o a photo-deviometer according to the present inve~tion.
Figure 2 is a front view of the photo-deviometer of Figure 1.
Figure 3 is a side view of the photo-deviometer of Figures l and 2 with a patient in posîtion.
Figures 4 and 5 are diagrams of the electrical system of the photo-deviometer of Figures 1, 2, and 3.
Figure 6 is a view of the camera fi~ation device and modified optics.
Description of Preferred Em~odimen~
Referring now to the drawings and particularly to Figure l, the photo-deviometer is generally indicated by . the rsference numeral 10 and includes a support structure 12, here shown as an adjustable tabl~. A deviometer disk 14 is mounted on the table 12 and i provided with a ~2230 centr31 fi~ation opening 16 and fi~ation images target 18 for deviometry measurements and fixation target or images 20 for extraocular dysunction measurement, here shown as an inner row 18 and an outer row 20 o~ fi~ation images.
5 Mounted adjacent one end of the tablP 12 is a recording device 22, here shown as a 35 mm camera, and mounted on the other side of the deviometer disk 14 is an adjustable headrest 24. The headrest 24 includes an adjustable chin rest 26 and an adjustable forehead headrest 28 for fixing 10 the patient's head, not shown, so that the patient's eyes are in a central fixation position with respect to the central fixation opening 16 and the lens 30 of the recording device 22 which is provided with the ring flash 32 mounted directly on the lens 30.
The inner and the outer row of fixation images 18 and 20 are positioned at the 12 o'clock, 1:30, 3:00, 4:30, 6:00, 7:30, 9:00 and ln: 30 positions.
As illustrated, recording device 22 is adjustable mounted on the table 12 for aligning the lens 30 o~ the 20 camera in a central fi~ation position with respect to the central fixation opening 16 and the plane of the film in the camera.
Th~ deviometer or image wall 14 is provided with images, not shown, positioned so that a patient can see theiimages when they are illuminated. Preferablyi the images selected are ~rom Walt Disney characters as the cartoon figures are easily identifiable by most children regardless of ethnic background and language barriers, they are not violent, and these characters will probably endure over future generations.
Also disposed on the table 12 are the selector switches ~4 for selectively illuminating the visual images on the inner and outer rows 18 and 20 of the deviometer disk 14.
Referring now to Figures 4 and 5, an electrical _9_ ~3~ ~23~

diagram is illustrated for illuminating the inner 18 and outer 20 images by the electric bulbs 19 and 21, respectively. Positive lines ~5 are con~ected to each of the switches 34 and to each of the bulbs 19 and 21, which 5 in turn are connected to the ground 23. Thus, activation of a switch 34 illuminates an image. No more description of the electrical systems for illuminating the images 18 and 20 is given or deemed necessary as any desired electrical system for this purpose can be used.
Referring now to Figure 2, the lens 30 of the camera is located in the central portion of the central fixation opening 16 of the disk 14. Referring now to Figure 3, a Patient "P~ has her head adjusted by the adjustable headrest 24 so that her eyes are directly in 15 line with the central fixation opening 16 to ths center of the lens 30 of the camera 22. Thus, the Patient "P"
focuses on the film plane as opposed to some point in between.
A 90 view finder is attached to the view finder 20 of the 35 mm SLR camera 22 which illuminates an accommodative targe~, a car~oon character, which is viewed by the Patient "P". This method of single illumination accommodative target has ~een selected so as to attract the patient's attention to that specific immage. This was done especially due to the fact that the operator must deal with young patients that often present with a low attention span. Thus, this system provides true central fixation. In the past, a single red diode mounted on the top o~ a flash was positioned under the front portion of a 35 mm macrolens to serve as a central ~ixation target, but this yielded inaccurat~ results fdrstly because it was a nonaccommodative target. Secondly, the subject ended looking at a ixation target that was too low and that was 22 cm away from the f ilm plane. The current central ixabion device was made partially possible by using a -lo- ~3~ 223~
number 9 endoscopic photo Fr~snel (a focusing screen from the Olympus Corporation). rhe number 9 Fresnel has a clear surface with its center, which is 23 mm in diameter, acting as a -tl8 Diopter lens. This in turn magnifies the 5 image that is pro~ected ~rom the 90 view finder through the SLR camera (22) and the macrolens system (30). Thus, the Patient "P" focuses on the film plane as opposed to some point in between and a true accommodative fixation devi~e is provided. The image is introduce~ simply by 10 using the proper illumination switch. The image also can be taken out of view by rotating a lever on the view finder or simply ramoving the 90 view finder from the SLR
camera eyepiece.
In the presence of manifest strabismus, the Patient "P" sees the image with only one eye and, therefore, the fixating eye or the preferred eye should be used to record accurate results. This can be achieved by using the cover test system. As this image is being projected to the Patient "P," the operator can depress 20 either a hand or foot switch and for one-sixtieth of a second, the mirror of the 35 mm camera 22 pops up (the image can no longer be seen) and the photograph of true central fi~ation is achieved. At this point, the image reappears to the patient until an alternate image is selected on the fixation wheel or disk l4. When the photograph is taken in this primary gaze, the light illuminating the image is turned off for a period of one-fiftieth of a second. This occurs so that the light traveling through the prism head and lens coming ~rom the 90 view finder will not afect the automatic e~posure of the SLR camera 22.
The camera 22 must, however, stay stationary, that is at the same elevation as the 3 and 9 o'clock fi~ation posi~ions to yield accurate and reproducible results. Since the distance from the Patient "P" to the r^~
3~2~3 1 lens 30 is fixed, it is not necessary to refocus between patients.
As an e~ample of a photo-deviometer according to the invention by which the foregoing advantagQous results 5 are achieved, a photo-deviometer 10 was constructed which included an adjustable table 120 cm in length and 42 cm in width. The circular wheel 14 with the inner and outer rows of fi~ation targets 18 and 20 was 54 cm in diameter with a 26.5 cm fi~ation opening 16 in the center. This opening was made so that a 35 mm SLR camera equipped with a ring flash could be positioned centrally on a mono pod 36. The visual images on the wheel 14 were mounted on the back of a blackboard shaped to ~it the wheel 14 which was positioned with strips of Velcro~onto the front part of the wheel. The image wheel could be interchange~ for new imayes at any time. The images selected, as previously mentioned, were Walt ~isney characters.
The recording device 22 was an Olympus OM-4 35 mm single lens reflex tSLR) camera with an autowinder sitting 20 on the monopod 36 and controlled either by a hand switch or a foot switch. A foot switch is very useful when doing a cover test or when photographing a down gaze wher~ both hands of the operator may be necessary to hold the eyelids of the patient open. Attached to the camera 22 was a 135 mm macrolens with a bellow extended to 17 cm. The f stop was preset at F22 for good depth of field. If desired, the camera can be fitted with a datapak that would imprint on the film, praferably in the lower right hand corner, the patient's identification number, the date or the time of the day.
An Olympus T-10 ring 1ash with recycling flash time of four seconds set on ASA 400 and the automatic position was used which was mounted directly on the macrolens 30 which was 52 mm in diameter~ Kodak Ectachrome EL-400ASA film wi~h a preset speed of 1/60th on *rrale ~IQrk -12- ~ 3~2230 the camera was used.
Highly satisfactory, accurate and reproducible measurements and photographs were obtained.
When performing deviometry measurements, the 5 operator normall~ sits on the let side when doing the right gazes and on the right side when doing the left gazes. When the photographs are taken, the same principle applies. Care must be taken to ensure that the patient is using the fixating eye when fixating at the different accommodative targets. This can be easily accomplished with the cover technique. The pediatric subject can be measured in either the standing or sitting position, on the parent's lap and, if older, in an e~amining chair. If desired, for added accuracy, a special counting grid used 15 in endothelial cell photography can be used. This grid has 2 mm squares. It is placed at the film plane of the camera and will help to measure any eye deviation.
The photo-deviometer according to the present invention allows both measurement and photographic 20 documentation of the strabismus in the cardinal positions of gaze. The photo-deviometer may be operated by only one person, be ~t the ophthalmologistJ ophthalmic photographer, or other allied help professio~al. The e~aminer can control the patient, the fi~ation target, and the SLR camera all at the same time Since both measurements and photographs are obtained simultaneously, this instrument has proved to be a time saving device.
By using the ring flash~ the operator will automatically produce a corneal specular reflection simulating the ~irshberg test. This can be very useful in evaluating one eye over the other.
Accordingly, the present invention attains the objects and ends and has the advantages and features mentioned as well as others inherent therein~
While presently preerred embodiments of the -13- ~3~23~

invention have been given ~or the purpos2s of disclosure, changes may be made therein which are within the spirit of the invention as deined by the scope and the appended claimsO

WHAT IS CLAIMED IS:

Claims (10)

1. A photo-deviometer comprising, a support structure, a camera mounted on the support structure, an adjustable headrest for fixing a patient's head mounted on the support structure and spaced from the camera, a deviometer disk mounted on the support structure between the camera and the head rest, the deviometer disk having a central fixation opening, the camera, headrest and deviometer disk arranged so that the patient's eyes when the headrest is in an adjusted position are on a central fixation image through the central fixation opening and in the camera's film plane, a plurality of fixation images on the deviometer disk facing the camera, provided with a manually activated switch for each of the fixation images operable to illuminate individually each of the fixation images, the camera provided with a viewfinder having a mirror arranged so that the patient sees the illuminated central fixation image in the mirror while in the central fixation position, whereby, the patient while in the central fixation position can look at, fixate on and accommodate to the illuminated central fixation image and a photograph can be taken of the patient's eyes while so doing.

2. The photo-deviometer of claim 1 where the plurality of fixation images comprise, an inner row and an outer row of fixation images.

3. The photo-deviometer of claim 2 where, there are eight inner and eight outer fixation images, the inner and outer fixation images being located at 12, 1:30, 3:00,

4:30, 6, 7:30, 9, 10:30 o'clock positions.

4. The photo-deviometer of claim 2 where, the inner row of fixation images is set for the deviometry measurements and the outer row of fixation images is set at a greater angle for the extraocular muscle dysfunction measurements in up and down gaze.

5. The photo-deviometer of claim 3 where, the inner row of fixation images is set at 25° and the outer row of fixation images is set at 34°.

6. The photo-deviometer of claim 1 where, the camera is a 35 mm camera provided with a ring flash mounted directly on its lens.

7. The photo-deviometer of claim 2 where, the camera is a 35 mm camera provided with a ring flash mounted directly on its lens.

8. The photo-deviometer of claim 3 where, the camera is a 35 mm camera provided with a ring flash mounted directly on its lens.

9. The photo-deviometer of claim 4 where, the camera is a 35 mm camera provided with a ring flash mounted directly on its lens.

10. The photo-deviometer of claim 5 where, the camera is a 35 mm camera provided with a ring flash mounted directly on its lens.