The National Eye Institute has identified age-related macular degeneration (AMD) as a major problem with increasing prevalence as the average lifespan increases. Recent advances at Scheie Eye Institute have included evidence of association between inflammation and iron overload with AMD. Retina Service ophthalmologists perform basic and clinical research and take care of patients in the practice.
What Is Age-Related Macular Degeneration?
Macular degeneration is the leading cause of severe vision loss in people over age 50 in the western world. This condition is also referred to as age-related macular degeneration or "AMD." In macular degeneration, vision loss occurs when the cells in the retina - the light sensitive region of the eye – start to break down. The most severely affected cells are those within a special region of the retina known as the macula, which is responsible for fine detail vision. The type of vision loss - central detail vision - affects reading, driving, sewing, watching TV, and any other tasks that requires focusing on small objects.
Although macular degeneration reduces central vision, side vision remains clear. Macular degeneration alone does not result in total blindness and most people continue to have some useful vision and are able to take care of themselves.
There are two main types of macular degeneration: "dry" and "wet."
Dry Macular Degeneration
Dry is the most common type of macular degeneration and vision loss is usually gradual. Some patients with dry AMD maintain good reading vision for their entire lives. In its early stages, changes in vision may be hard to notice. One may notice that straight lines appear wavy, or that there are blank spots in the center of vision. Colors may look dim. There is no way to restore vision lost from dry AMD. However, dry macular degeneration must be monitored because it can turn into wet macular degeneration.
Wet Macular Degeneration
Wet macular degeneration results when abnormal blood vessels form underneath the retina and leak blood or fluid thus causing that portion of the retina to bulge. This bulging of the retina distorts vision. An eye with wet macular degeneration will usually lose its ability to see fine detail, although prompt treatment may slow, minimize, and sometimes reverse vision loss. While only 10% of people with macular degeneration have the wet kind, it accounts for about 90% of the cases that lead to severe vision loss.
Causes of Macular Degeneration
Many older people develop macular degeneration as a part of the natural aging process. In addition to age, there are several characteristics that people with macular degeneration have in common. These include family history, smoking, or having blue or light colored eyes. Although seen as common factors in people with macular degeneration, it is not specifically known to what degree these characteristics actually increase one's risk for developing macular degeneration.
The development of drusen may also be a precursor to the development of macular degeneration.
What are drusen?
Drusen are deposits that lie beneath the retina. Drusen can be thought of as backed up waste products from various layers of the retina. Drusen can be a marker for macular degeneration (especially in the over 50 age group) because there appears to be an increased risk for macular degeneration as the number of drusen increases. Fat also accumulates in Bruch's membrane with age. This may also contribute to drusen formation.
Drusen occurs in two forms:
Hard, small: These do not increase with age and do not pre-dispose to macular degeneration
Soft, large: These are associated with age, may enlarge, and may predispose to macular degeneration.
Persons with large, soft drusen may also be at risk for subretinal bleeding.
Prognosis and Treatment for Drusen
The appearance of drusen is a common finding in older patients does not necessarily indicate the onset of vision loss. There is no clinically effective way to treat drusen. However, several clinical trials are underway to evaluate various methods, including laser treatments, and their effects on drusen reduction, and on the progression of macular degeneration.
It is very important to be followed closely by an ophthalmologist if drusen are present. On ophthalmologist can monitor subtle changes in the retina, and manage any complications that may arise. Persons with drusen should also perform a self-test called an Amsler grid, or a routine basis to monitor for the presence of visual distortions.