Intraocular lens implantation has become an increasingly popular addition to routine cataract extraction, especially with the wide patient acceptance that this method of aphakic correction has received. Although short-term follow-up studies have not revealed an increase in post-operative corneal edema due to endothelial damage in such cases, recent clinical studies using the specular microscope to visualize and count central endothelial cells in vivo have demonstrated a 30-70% decrease in endothelial cell density after lens implantation. These studies have not been confirmed and reasons for such a dramatic loss of cells are as yet unknown. The purpose of the recent proposal is to study the effect of intraocular lenses on corneal endothelium in a prospective, controlled clinical study. The specular microscope and pachometer will be used to follow changes in endothelial cell morphology, endothelial cell density, and corneal thickness (endothelial cell function) in patients undergoing routine intracapsular cataract extraction without lens insertion, compared to changes in patients undergoing extractions with addition of intraocular lens. The same experienced surgeons will perform all cataract extraction and the same intraocular lens will be employed throughout (Choyce Mark VIII). The major objective will be to confirm any effect of lenses on corneal endothelium and to determine reasons for these changes if present. Guidelines for patient selection for this procedure will hopefully be established based on such clinical trials.