F U N D U S P H O T O G R A P H Y BY E L E C T R O N I C F L A S H

P A R T IV. S I N G L E E X P O S U R E S T E R E O P H O T O G R A P H Y OF T H E F U N D U S

R O B E R T C . D R E W S , M . D .

Saint Louis, Missouri

A. I N T R O D U C T I O N

In Par t I I I of this series of papers, a new electronic flash fundus and anterior segment camera was described. In this re­port I shall show how this unit may be used to take single-exposure stereophotographs.

T h o m e r laid the foundation for stereo-ophthalmoscopy, in 1903, in his "Die Theorie des Augenspiegels."' He published the first Stereofundus photographs six years later.^ They were made through his reflex-free oph­thalmoscope by turning the instrument up­side-down between exposures.

Fur ther stereof undus photographs awaited the commercial production of the Norden­son camera. Nordenson himself wrote the first paper in 1926,' proposing that the pa­tient's head be made to lie horizontally first on one side and then the other in front of the camera. In 1927, papers appeared by Metzger,* Bedell,^ Wessely,« and Stock.' Metzger, Wessely, and Stock changed the patient's fixation between exposures and Bedell moved the camera. Excellent stereo-photographs have been made by all of these methods but none of them is reliable and none of them allows accurate calculation to be made from the photographs of differences in depth.

In 1930, Nordenson published the first "absolute," that is, simultaneously exposed, Stereofundus photographs.* They were made with the specially constructed Zeiss-Norden­son Stereofundus camera. In 1953, Norton described a method of making absolute Stereofundus photographs® by mounting a 35-mm. stereocamera on a Bausch and Lomb binocular ophthalmoscope and thus simul­taneously making the two exposures. Expo­sure time, however, becomes one second for Kodachrome." More recently^' Norton con­verted this unit to the use of an F A 5 Xenon

arc lamp. With the new high-speed Ekta­chrome film ( A S A 32) he can expose at l /20 th of a second.

B. STEREOTECHNiQUE

The crude method of taking two separate photographs from different angles is obvi­ously undesirable in photographing living material. However, making two photographs simultaneously on film which is then sepa­rated and mounted for viewing, is not en­tirely satisfactory either. Such subsequent mounting must be very accurately done, es­pecially if the photographs are to be pro­jected, and special double projectors must be used. Although companies like Eastman Kodak will return stereophotographs in stereo cardboard mounts, these mountings are not accurate enough for projection pur­poses and all such slides have to be re­mounted.

A much more satisfactory method for making stereophotographs is beginning to be employed by some European manufacturers, including Zeiss (Con tax ) , Leitz (Leica) , and Kern-Pail lard (Bo lex ) : the split-frame format. Stereolenses are mounted with their optical axes spaced one-half the film width apart, and two pictures are then made, one on each half of a normal film frame. The necessary effective displacement of the lenses for a natural stereo result is achieved by placing a mirror and /or prism system over the camera lenses. Such an effect can indeed be obtained with a single camera lens and a mirror system such as the Stereo-Tac unit made in this country or the new Ihagee adaptor for the Exakta cameras. Both Kin Dar and Ihagee have recently introduced systems for Exakta close-up photography, the former utilizing two lenses and the latter using one lens and a prism attachment.

633

634 ROBERT C. DREWS

The advantages of the split-frame format stereosystem are numerous. The camera body can be used both for stereo and for ordinary photographs merely by interchang­ing lenses. The stereophotographs are auto­matically aligned in mounting since they are never cut apart. Ordinary mounts can be used; thus special files are not needed. And finally, any ordinary projector may be used to show the pictures merely by replacing its lens with a special stereolens or by add­ing a mirror system over it.

C. C A L C U L A T I O N O F D E P T H

The use of absolute stereophotography would make possible the calculation of dif­ferences in depth of various parts of the fundus. The amount of papilledema or the height of a tumor for instance could be ex­pressed in millimeters and a quantitative evaluation made of their course in the third dimension.

Theoretically the difl^erence in depth (Δ) between two points on the fundus can be expressed as:

« ( d O a ) ' feyed,y , ,-Fdni(deye-feye)

íd02-t-SdÍ2 feycdil

Use of an approximate formula would in­troduce an error of less than five percent in any measurable lesion and would greatly facilitate calculations:

, 8(do2)'Mt S(dU)»

Assuming the patient's optic papilla to be 1.5 mm. in diameter:

Where : á = (the distance between the images of the two

points on one stereoframe) minus

(the distance between the images of the two points on the other stereoframe).

do2=the distance from the stereocamera lens to its object.

dÍ2=the distance from the stereocamera lens to the film.

S=the effective separation of the stereolenses. d e y e = the distance from the nodal point of the eye

to the fundus. fej.e = the focal length of the eye.

dni = the distance between the nodal point of the eye and the nodal point of the ophthalmo­scope lens.

dii = the distance from the ophthalmoscope lens to the image it forms of the fundus.

Ml=the total magnification of the image. This can be easily approximated by dividing the di­ameter in millimeters of the optic nerve on the photograph (φα) by 1.5: M t = -

Ί.5 _ . J . -=a set of values which can be com-b(dl2)' puted and marked on a "focusing" scale on the bellows. One would simply read and record this value whenever a stereophoto-graph were taken.

0„=the diameter of the image of the optic nerve on the photograph.

Thus the procedure for the quantitative determination of the height of a fundus lesion other than papilledema would be:

1. Take a stereophotograph of the lesion recording Q as read from a scale on the bellows device.

2. On the photograph, measure δ and øn. 3. Multiply these three values together. Note that values obtained by this simple

technique have some limitation in their use­fulness in comparing one patient with an­other because of our assumption that all pa­tients have optic papillae 1.5 mm. in diameter. This would be of no consequence in the usual case, however, where one is following a lesion in a given patient. W e are, however, trespassing upon research techniques: fur­ther elaboration of this subject does not belong in this paper, and may be presented later.

D . A P P A R A T U S

The fundus/anterior segment carnera unit described in Part I I I of this series can be very easily converted to stereophotography by replacing the camera lens with a suitably made stereolens system and adding appro­priate masks (fig. 1 ) . The focal length of the lenses used will depend somewhat on how large an area of retina one wishes to photograph. The separation of the optical axes in turn will depend on the choice of focal length. The mathematical extension of the split-frame format to hyperclose-up pho­tography, as in the fundus camera, leads

FUNDUS PHOTOGRAPHY 635

6 —

N O T T O S C A L E

Fig. 1 (Drews). Optical system for stereofundus photography using split-frame format. The drawing is a top view and is not to scale. (1) Fundus. (2) Image of the stereolenses formed in the pupil by the ophthalmoscope lens. (3) Ophthalmoscope lens. (4) Image of the fundus formed by the ophthalmoscope lens. (5) Stereolenses. (6) Images of the fundus on the film in split-frame format. For anterior segment stereophotography the ophthalmoscope lens is removed and the anterior segment itself placed at 4. To prevent overlapping images a mask is placed at 4 to limit image size. In fundus photography the mask may more easily be placed over the ophthalmoscope lens.

with gratifying satisfaction of all required conditions to a set of solutions, one of which is described in the next paragraph. This particular solution also satisfies Thorner ' s conditions for orthoplasty. '

The inexpensive stereolens system (fig. 2 ) used to take the photographs for this article was made from a pair of unmatched, war surplus doublets having focal lengths of about 91 mm. One edge of each was ground flat to allow the optical axes to be placed 10-mm. apart. The lenses were glued in a simple plastic holder. Optical alignment was not attempted.

E . O P E R A T I O N

Operation is no diflFerent from that for ordinary photographs. Unless a special stereofocusing system is incorporated, one

Fig 2. (Drews). Stereolens unit.

will focus on both images seen side by side. Wi th the new Ihagee Stereo Binocu­lar Viewfinder one can see the image in three dimensions for focusing.

F . RESULTS

With this technique stereophotographs of both the fundus and the anterior segment (fig. 3) can be made as easily and as reliably as ordinary electronic flash photographs. The relatively poor photographs used to il­lustrate this article were made with inferior lenses, poorly aligned, and are intended only to demonstrate the feasibility of such a stereosystem.

G. S U M M A R Y

Single exposure stereophotographs of both the fundus and the anterior segment have been made with the electronic flash fundus camera described in Pa r t I I I of this series of articles. Split-frame format has been used so that photographs can be made simply by exchanging a stereolens for the regular camera lens and adding a mask to the system. Such stereopictures can be filed in ordinary 35-mm. mounts and can be shown with an ordinary projector fitted with a stereolens. From such photographs it would be possible to calculate the differences in depth of various portions of the fundus.

636 ROBERT C. DREWS

Fig. 3 (Drews). Stereophotographs of tlie fundus and anterior segment. Masks were omitted for tlie fundus photograph, the images being allowed to overlap. The poor image quality and bad alignment are ascribable to the inferior quality of the lenses used and inaccuracies in gluing them together.

G E N E R A L S U M M A R Y

A series of four articles has been pub­lished showing how electronic flash can be successfully adapted to fundus photography. The work presented has been limited to clin­ically useful procedures and I have avoided more complicated techniques such as infra­red and ultraviolet, cataract, and motion-picture photography. A flicker-flash type power supply has been employed and the flash tube mounted in the camera on the opti­cal axis without intermediary optical systems. I have successfully employed this arrange­ment in an adapted carbon-arc camera and in a new fundus camera. The new camera can be quickly and easily converted to ante­rior segment photography and to single ex­

posure stereophotography of either the fundus or the anterior segment. High reso­lution black and white photographs of the fundus have been made with a narrow band filter, taking advantage of the high efficiency and brief duration of the electronic flash. Exposure time with the unit described is about l /3,000th of a second. Operation of electronic flicker-flash fundus cameras is un­usually simple. They are capable of uni­formly excellent color photographs.

F U R T H E R C O N S I D E R A T I O N S

An electronic flash tube has been fabri­cated in the proper size and shape and mounted directly where needed in an optical system, instead of having its light projected in by means of a supplementary optical sys­tem. The flash tube has a power supply which not only makes it flash in the usual manner but also makes it flicker rapidly at a low intensity when desired. It should be noted that this combination of principles has many other applications, such as cornea! pla-cidography and reflectography, photomicrog­raphy, photobiomicrography, macrophotog-raphy, endography, photo-elastic stress analysis, and so forth. With slight modifica­tion these principles can be used for motion-picture photography. Indeed this system can be applied wherever the use of electronic flash's instantaneous, cool, brilliant light has been desired but has not been possible be­cause of the necessity of focusing, compos­ing, adjusting lighting, determining expo­sure, and so forth, with the same light source that is used to take the picture. This system then allows qualitative and quantita­tive prediction and control of the photo­graphic effect of an electronic flash light source mounted directly where needed in an optical system.

7361 Cornell (5).

Patents pending.

R E F E R E N C E S

1. Thorner, W.: Die Theorie des Augenspiegels und die Photography des Augenhintergrundes. Berlin, Hirschwald, 1903.

FUNDUS PHOTOGRAPHY 637

2. -: Die stereoskopische Photographie des Augenhintergrundes. KUn. Monatsbl. f. Augenh., 47:481-490,1909.

3. Nordenson, J. W.: Stereoskopische Ophthalmographie durch einfache Aufnahmen. Upsala Lakaref. Fork.. 32:295-297, 1926.

4. Metzger, E.: Die Stereophotographie des Augenhintergrundes. Klin. Monatsbl. f. Augenh., 78 :338-348 1927

5! Bedell, Α. J.: Photographs of the fundus oculi. New York State J. Med., 27:951-971, 1927. 6. Wessely: Ber. Deutsch. Ophth. Ges. Heidelberg, 1927, p. 426. 7. Stock: Ber. Deutsch. Ophth. Ges. Heidelberg, 1927, p. 461. 8. Nordenson, J. W.: Ueber stereoskopische Photographie des Augenhintergrundes. Upsala Lakaref.

Fork., 35:216-222, 1930. 9. Norton, H. J., Jr.: Absolute three dimensional colored retinal photographs. Tr. Am. Acad. Ophth.,

57:612-613, 1953. 10. Personal correspondence. 11. Norton, H. J., Jr.: Absolute electronic retinal stereophotography. Am. J. Ophth., 40:809-817, 1955.

D I A M O X T O P R E V E N T H Y P H E M A A F T E R C A T A R A C T E X T R A C T I O N *

A N E G A T I V E REPORT

D E R R I C K V A I L , M . D . Chicago, Illinois

Wound reopening and hemorihage into the anterior chamber and in some cases into the vitreous, following cataract extraction, continues to be one of the most infuriating, depressing, and, on occasion, alarming of complications that occur in an otherwise smooth postoperative convalescence. I t occurs between the third and sixth day, usually in my experience early in the morning of the fifth day. The patient is awakened by a sudden sharp and severe pain and knows at once that something very serious has hap­pened to his eye. On dressing it, we almost always see bright fresh blood in varying amounts staining the eyepad. When the eye is opened, blood in varying amounts is seen in the anterior chamber. A close inspection of the wound reveals it to be edematous and congested, and the conjunctival flap boggy and raised. Fortunately, in most cases the blood slowly absorbs, and the visual result in the end is apt to be very good. In others, various complications that are the direct result of the accident, such as iritis, blood-

* From the Department of Ophthalmology, Northwestern University Medical School. Pre­sented at the 92nd annual meeting of the American Ophthalmological Society, Hot Springs, Virginia, June, 1956.

staining of the anterior hyaloid and some­times of the cornea, secondary glaucoma due to blockage of the filtration angle, and pro­lapse of the iris appear.

In the more severe cases, blood is found in the vitreous as well, and it may remain, slowly absorbing, for a month or more. In some of these cases, also, blood may be driven back in the root of the iris and pro­duce an iridodialysis, or even a cyclodialysis. Occasionally blood can be incarcerated be­neath the anterior hyaloid of the herniation of the vitreous.

In a relatively few cases, not studied here, there is a late subchoroidal hemorrhage that no doubt would have been expulsive had not the wound held for the most part. Eyes with this compHcation are almost always lost. If the condition can be recognized very early, it is possible to rescue such an eye from total loss by a scleral puncture and evacuation of the subchoroidal blood, but such a dramatic success must be exceedingly rare.

In a study of hyphema occurring in ap­proximately seven percent of 1,185 cases of cataract extraction reported by me in 1941, the following conclusions were reached:

1. Hyphema is the result of wound re-