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Slit-Lamp Beamsplitter for Two Stereoscopic Views
718
AMERICAN JOURNAL OF OPHTHALMOLOGY
SLIT-LAMP BEAMSPLITTER FOR TWO STEREOSCOPIC VIEWS BRUCE E. COHAN, M.D. Ann Arbor, Michigan AND JACK C. URBAN Burbank, California
The slit-lamp microscope is the basic instrument for examining the anterior segment of the eye; it is used extensively in gonioscopy, fundus examination, and for such measurements as applanation tonometry and ophthalmodynamometry. Slit-lamp examination techniques depend on building up detail through fine focus, vertical and lateral movements of the mi croscope, and variations of the illumina tor angle and slit length and width; in gonioscopy and fundus examination, sub tle tilting of the special lenses also con tributes to this detail. Teaching each tech nique is slow and difficult because of the dynamic nature of the slit-lamp view and the effect of patient eye movement. While photography can demonstrate the end point of measurement techniques, it lacks the richness of the dynamic slit view because of the static, usually monocular, nature of a photograph. The slit lamp is also used in surgical maneuvers, like the removal of a corneal foreign body, and has recently been ap plied to more complex procedures inside the eye, such as incising a pupillary mem brane and repositioning a dislocated loop of an intraocular lens. In this type of surgery an important advantage of the slit lamp is the quality of slit illumination, especially for diaphanous membranes, From the Department of Applied Mechanics and Engineering Science, College of Engineering, Uni versity of Michigan, Ann Arbor, Michigan. This study was supported in part by Public Health Serv ice Research Grant EY 01076 from the National Eye Institute. Reprint requests to Bruce E. Cohan, M.D., 2350 Washtenaw Ave., Ann Arbor, MI 48104.
MAY, 1978
which is superior to that of surgical mi croscopes. However, until now surgery at the slit lamp has been performed with one hand, while the other hand adjusts both microscope and illuminator. The limitations in teaching slit-lamp examination techniques were partial ly overcome in 1958, when one of us (J.C.U.) designed a monocular observa tion tube for attachment to a modified Zeiss binocular. Subsequently, beam splitters placed before the Zeiss binocu lar were developed for transmitting light from one optical train to a monocular observation tube. These observation tubes have the critical limitation of the mon ocular view in that they deny the ob server the subtle appreciation of depth, which is a major advantage of the stereo scopic slit-lamp view. Recently, HaagStreit developed a monocular microscope for two observers, which is not used si multaneously with the principal stereo scopic microscope, and thus limits both the examiner and the observer to a mo nocular view. Finally, Zeiss provides a binocular which attaches to their observa tion tube; but since it has access to only one optical train, the result is not a stereo scopic view. We have developed a double binocular beamsplitter (Fig. 1), compatible with Zeiss optics, which splits the light from each optical train of the microscope to an observation binocular. This affords the observer the exact stereoscopic view of the examiner. This beamsplitter can be attached to a Zeiss slit lamp (Fig. 2). It can also be attached to a Haag-Streit slit
Fig. 1 (Cohan and Urban). Double binocular beamsplitter with Zeiss binoculars.
VOL. 85, NO. 5
NOTES, CASES AND INSTRUMENTS
Fig. 2 (Cohan and Urban). Double binocular beamsplitter attached to a Zeiss slit lamp.
lamp which has been modified by replac ing its microscope with a Zeiss micro scope (Fig. 3), a modification devised in 1968 by Professor R. Witmer of the Universitats-Augenklinik, Zurich (W. Neihardt, Haag-Streit AG, personal com munication, 1977). In addition to its dra matic benefits for teaching examination techniques, the double binocular beam splitter is important for surgery at the slit lamp. It allows the observer to become an assistant who controls the microscope po sition and illuminator adjustments. Thus the surgeon has both hands free, one to stabilize the eye and the other for surgical maneuvers; or both hands can be used in
719
Fig. 3 (Cohan and Urban). Double binocular beamsplitter attached to a Haag-Streit instrument, modified by replacing its optics with Zeiss optics.
surgery while the assistant stabilizes the eye. SUMMARY
A double binocular beamsplitter, com patible with Zeiss optics, splits the light from each optical train of a slit-lamp microscope to provide an observer the exact stereoscopic view of the examiner. It has advantages in teaching slit-lamp examination techniques. Further, in sur gery at the slit lamp, it allows the observer to function as an assistant and the sur geon to have both hands free.
AMERICAN JOURNAL OF OPHTHALMOLOGY
SLIT-LAMP BEAMSPLITTER FOR TWO STEREOSCOPIC VIEWS BRUCE E. COHAN, M.D. Ann Arbor, Michigan AND JACK C. URBAN Burbank, California
The slit-lamp microscope is the basic instrument for examining the anterior segment of the eye; it is used extensively in gonioscopy, fundus examination, and for such measurements as applanation tonometry and ophthalmodynamometry. Slit-lamp examination techniques depend on building up detail through fine focus, vertical and lateral movements of the mi croscope, and variations of the illumina tor angle and slit length and width; in gonioscopy and fundus examination, sub tle tilting of the special lenses also con tributes to this detail. Teaching each tech nique is slow and difficult because of the dynamic nature of the slit-lamp view and the effect of patient eye movement. While photography can demonstrate the end point of measurement techniques, it lacks the richness of the dynamic slit view because of the static, usually monocular, nature of a photograph. The slit lamp is also used in surgical maneuvers, like the removal of a corneal foreign body, and has recently been ap plied to more complex procedures inside the eye, such as incising a pupillary mem brane and repositioning a dislocated loop of an intraocular lens. In this type of surgery an important advantage of the slit lamp is the quality of slit illumination, especially for diaphanous membranes, From the Department of Applied Mechanics and Engineering Science, College of Engineering, Uni versity of Michigan, Ann Arbor, Michigan. This study was supported in part by Public Health Serv ice Research Grant EY 01076 from the National Eye Institute. Reprint requests to Bruce E. Cohan, M.D., 2350 Washtenaw Ave., Ann Arbor, MI 48104.
MAY, 1978
which is superior to that of surgical mi croscopes. However, until now surgery at the slit lamp has been performed with one hand, while the other hand adjusts both microscope and illuminator. The limitations in teaching slit-lamp examination techniques were partial ly overcome in 1958, when one of us (J.C.U.) designed a monocular observa tion tube for attachment to a modified Zeiss binocular. Subsequently, beam splitters placed before the Zeiss binocu lar were developed for transmitting light from one optical train to a monocular observation tube. These observation tubes have the critical limitation of the mon ocular view in that they deny the ob server the subtle appreciation of depth, which is a major advantage of the stereo scopic slit-lamp view. Recently, HaagStreit developed a monocular microscope for two observers, which is not used si multaneously with the principal stereo scopic microscope, and thus limits both the examiner and the observer to a mo nocular view. Finally, Zeiss provides a binocular which attaches to their observa tion tube; but since it has access to only one optical train, the result is not a stereo scopic view. We have developed a double binocular beamsplitter (Fig. 1), compatible with Zeiss optics, which splits the light from each optical train of the microscope to an observation binocular. This affords the observer the exact stereoscopic view of the examiner. This beamsplitter can be attached to a Zeiss slit lamp (Fig. 2). It can also be attached to a Haag-Streit slit
Fig. 1 (Cohan and Urban). Double binocular beamsplitter with Zeiss binoculars.
VOL. 85, NO. 5
NOTES, CASES AND INSTRUMENTS
Fig. 2 (Cohan and Urban). Double binocular beamsplitter attached to a Zeiss slit lamp.
lamp which has been modified by replac ing its microscope with a Zeiss micro scope (Fig. 3), a modification devised in 1968 by Professor R. Witmer of the Universitats-Augenklinik, Zurich (W. Neihardt, Haag-Streit AG, personal com munication, 1977). In addition to its dra matic benefits for teaching examination techniques, the double binocular beam splitter is important for surgery at the slit lamp. It allows the observer to become an assistant who controls the microscope po sition and illuminator adjustments. Thus the surgeon has both hands free, one to stabilize the eye and the other for surgical maneuvers; or both hands can be used in
719
Fig. 3 (Cohan and Urban). Double binocular beamsplitter attached to a Haag-Streit instrument, modified by replacing its optics with Zeiss optics.
surgery while the assistant stabilizes the eye. SUMMARY
A double binocular beamsplitter, com patible with Zeiss optics, splits the light from each optical train of a slit-lamp microscope to provide an observer the exact stereoscopic view of the examiner. It has advantages in teaching slit-lamp examination techniques. Further, in sur gery at the slit lamp, it allows the observer to function as an assistant and the sur geon to have both hands free.