Corneal endothelial cells in mono- and di-zygotic twins.

Noncontact specular microscopy was used to examine the corneal endothelia of monozygotic (MZ) and dizygotic (DZ) twins in the age groups 25-34, 35-49, and 50-69 years. Endothelial photographs were analysed in respect of 100 individual cells from both eyes of 48 subjects. The mean cell areas in MZ twins showed a strong positive pairwise correlation (r (RE) = 0.727, r (LE) = 0.933), but there was no statistically significant pairwise correlation in DZ twins (r (RE) = 0.080, r (LE) = 0.167). Statistically significant pairwise correlations were also found when the lowest or highest deciles of cell areas in MZ twins were compared, but not when respectively compared in DZ twins. It would seem that environmental factors have little effect upon pleomorphism and increase in cell area with increasing age. The endothelial cell characteristics in normal individuals seem to be mainly determined by genetic factors.