Structure and function of the corneal endothelium in diabetes mellitus type I and type II

Objective: To measure and compare corneal endothelial morphologic characteristics and function in subjects with diabetes mellitus types I and II. Design: Forty-nine patients with diabetes mellitus type I and 60 patients with diabetes mellitus type II were recruited from the active practice of the Mayo Clinic, Rochester, Minn. Thirty-one normal subjects, divided by age into two overlapping groups of 20 each, served as controls. Corneal endothelial permeability and corneal autofluorescence were measured by fluorophotometry. Central corneal endothelial photographs were taken with a wide-field specular microscope, which also measured the corneal thickness. Results: Neither the type I nor the type II diabetics differed from their controls in endothelial permeability and endothelial cell density. The type I diabetics had polymegethism, pleomorphism, increased corneal thickness, and increased corneal autofluorescence compared with their controls. Similar measured values were found in the type II diabetics, but they did not differ significantly from those of their age-matched controls. The type II diabetics were older than the type I diabetics, and the older control group showed changes similar to those seen in the diabetics; these changes were presumably associated with aging. The severity of retinopathy was significantly correlated only with corneal autofluorescence. Conclusions: The corneas of patients with type I diabetes mellitus exhibit abnormalities in endothelial cell morphologic characteristics and corneal autofluorescence. The changes resemble those that occur with aging in normal subjects, making them difficult to discern as abnormal in type II diabetics, who are usually older. We found no abnormalities in endothelial permeability in either type I or type II diabetics.