Endothelial cell density and thickness of the cornea do not appear to be affected by long-standing diabetes mellitus. Standard intra- or extracapsular cataract surgery results in a statistically significant reduction of endothelial cell density, but not in a long-term change of corneal thickness. Endothelial cell loss after trans pars plana surgery averages 8.5%. Differences in endothelial cell loss between phakic eyes of diabetics and phakic and aphakic eyes of nondiabetics subjected to lens removal and/or vitrectomy are not statistically significant. Corneal thickness is increased to a statistically significant degree in all eyes after trans pars plana surgery. Although the cornea in diabetics requires more time to recover after trans pars plana surgery, we found no evidence that it suffers significantly more damage than the cornea in nondiabetics.