An ultrastructure study of posterior polymorphous dystrophy of the cornea.

The cornea from an early developing and uncomplicated case of posterior polymorphous dystrophy in a 15-year-old boy shows a thin abnormal Descemet's membrane and reduced number of endothelial cells as the primary findings. Ultrastructurally, the membrane was composed of a very thin, three-dimensional lattice pattern layer covered by layers of fibrous material. This lattice pattern is normally formed between late fetal and early adolescent life. The 3 previously reported histologic cases of this entity were from cases with long-standing corneal opacities in the late third to fifth decade of life with additional corneal changes. However, in each case the lattice pattern layer of the membrane was abnormally thin. This report suggests that a progressive form of posterior polymorphous dystrophy of the cornea is due to cells forming abnormal Descemet's membrane beginning in late fetal life to soon after birth.