macular degeneration

macular degeneration eye disorder causing loss of central vision. The affected area, the macula, lies at the back of the retina and is the part that produces the sharpest vision. The most serious visual impairment occurs when abnormal blood vessels form and leak serous fluid or bleed into the tissue of the macula, ultimately producing scar tissue. Peripheral (side) vision is unaffected. Onset may be acute with hemorrhage but usually is gradually progressive. Although some vision is retained, the ability to read, recognize faces, and drive a motor vehicle is greatly reduced. The condition is painless.

Macular degeneration is a major cause of vision impairment among elderly people. Although its underlying cause is unknown, it sometimes appears to run in families. Serious macular degeneraton, if diagnosed early, may have its progress stemmed by laser or photodynamic (cold laser and drug) treatment that closes leaking vessels. Antiangiogenic drugs, which inhibit the formation of new blood vessels, can be injected into the eye to stop degeneration and in some cases even improve vision. Sudden change in vision in someone over age 50 thus requires immediate medical attention.

Bibliography: See H. Grunwald, Twilight: Losing Sight, Gaining Insight (1999).

macular degeneration n. a group of conditions affecting the macula lutea of the eye, resulting in a reduction or loss of central vision. age-related m. d. (AMD, ARMD) the most common cause of blindness in the elderly. Atrophic or dry AMD results from chronic choroidal ischaemia: small blood vessels of the choroid, which lies beneath the retina, become constricted, reducing the blood supply to the macula. This gives rise to degenerative changes in the retinal pigment epithelium (RPE; see retina). Wet AMD is associated with the growth of abnormal new blood vessels under the retina, derived from the choroid (see (choroidal) neovascularization). These can leak fluid and blood into the RPE, which further reduces macular function.
www.rnib.org.uk/xpedio/groups/public/documents/publicwebsite/public_rnib003635.hcsp Information about macular degeneration from the Royal National Institute of the Blind