[Pinguecula and pterygium: histologic and electron microscopic study (author's transl)].

Two pingueculae combined with pterygia were studied by light and electron microscopy. Hyaline degeneration of the collagen, dark staining granular, von Kossa negative concretions and elastotic material were observed in both conditions together with marked changes in the fibroblasts, endothelial cells, pericytes and the basement membrane of conjunctival capillaries and small veins. The elastotic material is similar to that observed in solar elastosis, where the collagen fibers are less severely damaged. Chronic sun exposure of the pericorneal conjunctiva may damage endothelial cells primarily and disturb vascular exchanges. This would result in accelerated degeneration and regeneration of endothelial cells, in thickening of the basement membrane and, secondarily, disturbed metabolism of fibroblasts with alterations of the collagen and elastic fibers.