Morphologic and clinical features of retrocorneal melanin pigmentation and pigmented pupillary membranes: review of 225 cases.

Observations based on clinical and histopathologic data from 200 consecutive cases of retrocorneal pigmentation by melanin-containing cells (RCP) and 25 cases of pigmented pupillary membranes (PPM) are reported. RCP was observed to be formed by four cell types, either alone or in combinations. The characteristic morphologic appearance of each cell type is described, and the significance and the predisposing factors for the various forms of RCP are outlined. RCP from endothelial-cell pigment phagocytosis, and in cases of resulting pigmented macrophages, was found to be a rather nonspecific reaction to release of pigment granules of iris pigment epithelium after surgical trauma, inflammation, and with the pigment dispersion syndrome. RCP from iris pigment epithelium was especially associated with anterior segment trauma with iris incarceration and peripheral anterior iris synechiae. This form was the least frequent. Most frequent in this series was RCP from iris stromal melanocytes. This seemed to be stimulated by surgical or accidental trauma and by corneal inflammation. Iris melanocytization of the anterior chamber angle and posterior corneal surface appeared to be related to the formation of retrocorneal fibrous tissue, the presence of anterior synechiae, and the development of secondary open-angle glaucoma. PPM are formed mostly by a combination of the pigmented cells of the iris. The predisposing conditions for formation of PPM were the same as for RCP. However, no correlation of implicated cell types and predisposing factors was detected. With these findings the importance of iris tissue, especially iris stromal melanocytes, in these basic reactions to anterior segment trauma or corneal inflammation is discussed.