OBSERVATION OF THE RETINA USING THE TANDEM SCANNING CONFOCAL MICROSCOPE

A tandem scanning confocal microscope (TSCM) is currently being used t o obtain high-resolution images of the human cornea in vivo. Advantage s of confocal microscopy for in vivo imaging include optical sectionin g and increased contrast through removal of scattered light. We have a dapted rile TSCM to view the retina in vivo by constructing an applana ting lens and fitting the microscope with an imaging-intensifying came ra of increased sensitivity. The microscope uses a spinning disc with 40,000 holes, each of 30 microns diameter, and a 100 W mercury are lam p light source with a 455 nm long pass filter. The applanating lens is composed of three elements, two of which are movable for focusing, Im ages of a rabbit retina were obtained in vivo revealing the nerve fibe r layer and blood vessels around the optic disc, The power density at the retina was calculated to be 3 mW/cm(2), which is well below the po wer levels of a direct. or indirect ophthalmoscope. Magnification of t he retinal image was approximately 60 x and a 1 mm wide area of retina was in view, This prototype TSCM system demonstrates that images of a retina in vivo are obtainable with confocal microscopy and that the s harpness is comparable to standard fundus camera photography. Further modifications to improve the light level and alterations in the design of the objective should improve the quality of the images obtained an d achieve the enhanced resolution of which, in theory, the confocal mi croscope is capable.