Optic nerve blood flow in glaucoma.
BACKGROUND: Glaucomatous optic neuropathy often occurs in the absence of elevated intraocular pressure and, conversely, elevated intraocular pressure may occur without associated damage of the optic nerve. These findings challenge the simple explanation of intraocular pressure being the sole cause of neural loss and have led to theories of ischaemic causes of the morbidity. This paper reviews the vascular anatomy of the optic disc, the factors that control its blood flow and the existing techniques for measurement of the blood flow. It also briefly discusses the possible role of apoptosis in glaucomatous visual loss. METHOD: Literature review. CONCLUSIONS: The posterior ciliary artery circulation is the main source of the blood supply to the optic nerve head with additional lesser supply via the central retinal artery and the choroidal circulation. There is considerable individual variation in the distribution of this circulation and complex regulatory systems govern its function. It is likely that microcirculatory changes in the vascular supply of the optic disc play a role in glaucoma, either as the primary abnormality or as a co-factor that increases susceptibility to damage from increased intraocular pressure through impaired auto-regulation. Clinical trials are currently in progress for the treatment of glaucoma with systemically administered agents that are antagonists of the receptors that mediate glutamine toxicity, a factor in the process of apoptosis.
Bathija
Renuka
R
Glaucoma Unit, The Royal Victorian Eye and Ear Hospital, 32 Gisbourne Street, East Melbourne, Victoria, 3002, Australia.