Specular microscopy of the corneal endothelium

Although it is possible to observe the individual cells of the corneal endothelium with the use of the biomicroscope and specular illumination (Vogt, 1919), eye movements and the limited magnification available virtually preclude the use of this technique for systematic study of the endothelium. These problems have been largely overcome by the introduction of the specular microscope (Maurice, 1968), which was subsequently adapted for clinical use by replacing the original water immersion lens with a dipping cone objective which applanates the cornea (Laing et al., 1975). With this instrument it is possible to examine and photograph the corneal endothelium at high magnification in vivo. Several authors have published their findings with the clinical specular microscope (Laing et al., 1976a, b; Bourne and Kaufman, 1976a, b, c; Bourne et al., 1976), and the optical principles have been discussed (Bourne and Enoch, 1976). Recently the use of an auxiliary lens to obtain a wider field of view has been described (Sherrard, 1976). The purpose of the present study was to quantify the method of sampling corneal endothelial cell density with the specular microscope. Endothelial cell counts were performed on 67 subjects of various ages and the following 4 parameters were investigated-the reproducibility of axial cell counts, the relationship between axial and peripheral cell counts in the same eye, the relationship between axial cell counts from pairs of eyes, and the variation in axial cell density with age.