Fine structural significance of bone corpuscle-shaped pigmentation in the human retinal pigment degeneration

Two cases of advanced RPD were observed their trypsin digested vascular trees and retinal substructures, especially RPE and pigmented cells in the neural retina. In the both eyes the visual cell was almost completely degenerated to disappear except posterior regions and apical part of RPE came to contact with neural retina or external limiting membrane formed by tight junction between adjacent Müller cell processes. Occasionally RPE in the equatorial region had completely disappeared and was replaced by Müller cell processes which was directly apposed to the Bruch's membrane. Pigmented cells were observed at almost all levels of the neural retina and along the intraretinal capillary. Pigmented cells were classified into three types. The first type of the cell was corresponded with the macrophage in the substructural features. The second type of the cell was RPE proliferated or migrated into the neural retina forming bone corpuscle-shape pigmentation in the retina and along the intraretinal capillary. Müller cell processes also indicated up-taking pigment granules, that is, the third type of the pigmented cell.