Macular degeneration is a condition in which the macula, the central part of the retina, degenerates. This is where most of the images formed by the lens are sent and it is much more sensitive to detail than the peripheral retina. The macula provides the central or close up vision necessary for detailed activities such as reading. Yellowish deposits called drusen accumulate beneath the retina of the eye. Loss of vision can start at the edge of the visual field and work its way towards the center or it may start in the center and work its way outwards.
There are two kinds of macular degeneration: dry and wet. Dry macular degeneration accounts for 85 to 90 per cent of cases and wet macular degeneration accounts for approximately 10 per cent. In dry macular degeneration, drusen is deposited in the macula without any evidence of scars, blood, or other fluid leakage. In wet macular degeneration, leaked material forms a mound, often surrounded by small hemorrhages. Eventually the mound contracts, leaving a scar. Both forms of macular degeneration usually affect both eyes at the same time. The dry form develops slowly and usually causes mild vision loss. The wet form is a much greater threat to vision and is indicated by a large blind spot in the middle of the visual field.
Age-related macular degeneration is the most common cause of blindness in developed countries and affects about 6 per cent of Americans between the ages of 65 and 75 and almost 20 per cent of those aged over 75.
Macular degeneration leads to a painless loss of vision. Symptoms include night blindness, blurry or fuzzy vision, straight lines appearing as wavy ones, a dark or empty area in the center of vision, narrowed blood vessels in the retina and gradual development of poor vision that can lead to total blindness.
It is unclear exactly why macular degeneration develops and there is currently no cure. Risk factors for the disorder include high blood pressure, cardiovasculardisease, nutritional deficiencies, exposure to certain chemicals, and heredity. Light eye pigmentation and cigarette smoking may also be risk factors. Some experts believe that long-term exposure to light causes free radical damage to the retina, and that this contributes to the development of macular degeneration.
Some forms of macular degeneration can be treated with laser surgery and low vision aids can be useful in allowing people to continue normal activities. Sunglasses may be useful in preventing light damage.