Abstract

High magnification, clinical microscopy of the cornea has been made practical by the use of optical elements that contact the surface(1), thereby establishing focus and damping involuntary lateral movements. Specular microscopes, used for examination of the endothelial cell layer, make use of so-called dipping cones that attach to the front of a long working distance objective. Generally they employ a flat front surface and a spherical rear surface that is concentric to the focal plane. This design increases the numerical aperture of the system by a factor equal to the refractive index of the cone material. The aberrations introduced are negligible for low numerical aperture systems, typically NA 0.35. While this numerical aperture is sufficient for endothelial and superficial epithelial cell examinations, a higher resolution is desirable for studies of detail within the stroma.

© 1992 Optical Society of America