Ocular ochronosis. Clinicopathological, histochemical, and ultrastructural studies

Presented here are the clinical, histological, histochemical, and ultrastructural findings of an eye with notable ochronotic changes. Ochronotic pigment is seen by light microscopy as amber globules or fiber-like structures in the cornea, conjunctiva, and sclera combined with degenerated collagen. In the area of a previous injury the intense involvement of the cornea, which is usually not notably involved, indicates the role of preexisting degeneration for the development of clinically visible pigmentation. Although the ultrastructure of the ochronotic pigment is similar to melanin, the chemical behavior is different and, it seems, similar to elastin. Ultrastructurally, most of the pigment granules are extracellular, partly altering the collagen fibers and fibrocytes. The electron-microscopically observed four patterns of deposition are interpreted as stages in the development of ochronotic deposits, according to biochemical findings in the literature.