(Age-related Macular Degeneration · AMD)
In this condition factsheet:
The Facts on Macular Degeneration
The macula is a tiny circle in the middle of the retina, a light-sensitive membrane that lines the inside of the back of the eye. In older people, it sometimes begins to deteriorate or degenerate for unknown reasons. Women are believed to be more at risk than men. Macular degeneration is the leading cause of legal blindness in Canada, accounting for 34% of cases. However, macular degeneration rarely leaves you totally unable to see.
There are two types of this disease:
- Dry macular degeneration accounts for about 90% of cases. The tissue of the retina shrinks and pigments accumulate inside of it. Dry macular degeneration can progress to the wet form.
- In wet macular degeneration, new blood vessels grow around and behind the macula. There's sometimes bleeding in or behind the macula. Material seeps into the retina and settles in the macula. This is called an exudate. Eventually the exudate disappears, but a scar takes its place. All people who have wet macular degeneration had dry macular degeneration first.
Causes of Macular Degeneration
The causes of macular degeneration are unknown, but the risk grows with age. Because it's extremely rare in people under age 50, the condition is usually referred to as age-related macular degeneration (AMD).
There are some known risk factors for macular degeneration. Smoking may increase your chances of developing the condition and seems to speed up its progress. High cholesterol levels, high blood pressure, obesity, and a diet lacking in dark green leafy vegetables and omega-3 fatty acids may also be associated with macular degeneration. Women seem to be at a higher risk than men.
Macular degeneration runs in some families but not in all. Recent studies of twins suggest that both genes and environment contribute to the onset of macular problems. Wet macular degeneration, at least, seems to be more common in people with poor cardiovascular health. Although it only accounts for about 10% of the cases, wet macular degeneration is responsible for 90% of the blindness caused by this disease.
Symptoms and Complications of Macular Degeneration
Both types of macular degeneration are completely painless. In dry macular degeneration, the centre of the field of vision in an eye slowly blurs or grows dim. You can still see colours, but the details aren't clear. This tends to happen over a period of years. Often, people don't notice the early stages, especially if the other eye is working fine.
Unfortunately, macular degeneration rarely affects just one eye. It may take time, but the other eye may eventually start to develop the same problems.
The vision loss in wet macular degeneration is much more rapid. While the central part of the field of vision fades and blurs, it usually vanishes completely, leaving a large blind spot. An early sign of wet macular degeneration is when you notice that lines in the centre of the field of view become wavy. This is due to the new blood vessels leaking fluid under the macula, which lifts it from its bed and deforms its shape. Wet macular degeneration usually occurs in one eye at a time.