Vascular and glial changes in the retrolaminar optic nerve in glaucomatousmonkey eyes

Vascular and glial changes of the retrolaminar optic nerve were studied in monkey eyes with increased intraocular pressure (IOP) from 1 to 4 years and with different stages of optic nerve atrophy. In histological cross-sectio ns of retrolaminar optic nerves of 11 rhesus and 6 cynomolgus monkeys the e ntire area, number of axons and vessels and area of pial septa were quantit ated and three different kinds of nerve degeneration classified. Ultrathin sections of these different stages were performed and the number of open an d occluded vessels was determined. In addition, in cynomolgus monkey optic nerves immunohistochemical staining for alpha B-crystallin, glial fibrillar y acidic protein (GFAP) and vimentin was performed. Even in animals with th e same duration of glaucoma and comparable mean IOP values the axon degener ation varied considerably. Independently of axon loss the number of capilla ries in the rhesus monkeys remained constant, whereas there was a slight de crease in the cynomolgus monkeys. Some of the vessels, especially in the mo st severely damaged regions, were occluded. The density of glial cells incr eased whereas the total number remained nearly constant. In control section s all astrocytes stained for GFAP and alpha B-crystallin. In the glaucomato us optic nerves the density of alpha B-crystallin- and GFAP-positive cells was significantly increased. The vascular reaction in the retrolaminar glau comatous optic nerves differs from that described in the prelaminar region. We assume that in the postlaminar region in areas with diminished nutritio nal needs vessels occlude and finally degenerate. Copyright (C) 2000 S. Kar ger AG, Basel.