Quantitative endothelial biomicroscopy.

Twenty patients were evaluated by quantitative endothelial biomicroscopy and the resulting endothelial cell densities compared with those from a specular microscope. Estimated cell densities by this technique, when compared with the specular microscope, demonstrated a Pearson correlation coefficient of +0.977, an average error of -7% and an absolute error of 12%. There were no errors greater than 26% except for one extremely low cell density of 318 cells/mm2 for which the estimate was 476 cells/mm2. This rapid, inexpensive technique requires counting the number of endothelial cells seen across the horizontal diameter of the 0.2-mm projected spot beam of a standard biomicroscope. From this count and the known spot size the endothelial cell density may be accurately calculated. A simplified four-step technique for performing specular microscopy using only the standard biomicroscope and a method for accurately measuring the size of the projected slit lamp spot beam are explained.