Filter mount system for the miniature indirect binocular ophthalmoscope.

Since the introduction of the indirect ophthalmoscope by Schepens (I947), the field of ophthalmology has witnessed an increasing sophistication in the instrument (Hovland, Elzeneiny, and Schepens, I969; Weaver, I 970). The recently introduced miniature indirect binocular ophthalmoscope of Schultz and Crock (Crock, Galbraith, and Parel, I969) offers a lightweight spectacle-frame instrument with a portable rechargeable battery supply. This instrument has proved to have excellent optical qualities and to give sufficient light for examination and surgery of the retina in consulting room and hospital. The value of the indirect ophthalmoscope in viewing the fundus fluorescein angiograms has been noted by Gass, Sever, Sparks, and Goren (I967). When it is used in combination with the fundus camera and contact lens slit-lamp examination, a thorough evaluation of the retinal status may be obtained. For the indirect ophthalmoscopic examination, either a cobalt blue or a Wratten 47A filter is interposed in the instrument's light beam to permit the visualization of the fluorescein pattern. Most of the commercially available indirect ophthalmoscopes offer, either by a swinging mount or by a rotating dial, a means of selectively introducing the desired filter, but the Schultz-Crock Indirect Ophthalmoscope does not provide such a carrying system. Because of the acceptability of the Schultz-Crock instrument, a filter-carrying system has been devised and is described below.