A new contact glass for slit-lamp examination of the cornea, especially in specular reflection

A new contact glass of 2.2X magnification for the examination of the cornea is described. With it, all three types of illumination provided by the slit lamp can be used to advantage: specular reflection, optical section, and indirect light. A precorneal chamber filled with liquid abolishes the surface reflex of the tear film, and a built-in orange filter suppresses most of the light scattered by the corneal stroma. In specular examination the necessity for a large angle between the illumination and observation beams no longer exists, so that quite small angles can be used. Since at the same time such a glass considerably widens the usable field, epi- and endothelioscopy are greatly facilitated. Handling of the glass is as easy as in routine biomicroscopy. It is shown that a contact glass of power M increases the resolution in depth by a factor of M2. Image distortion introduced by the glass is measured and found to be tolerable within the area of photographic records usable for cell density determinations. Some modifications made on the Nikon FS-2 photo slit lamp in order to improve its suitability for endotheliography are described. Clinical application of the method is documented by several examples.