When healthy, the middle of the retina, called the macula, provides clear images in the center of what the eyes see. With age-related macular degeneration, gradually accumulating damage to the macula causes a blind spot in the center of vision that interferes with daily activities such as driving, seeing details, and reading. According to the National Eye Institute, age-related macular degeneration is the leading cause of loss of vision in people over the age of 60 in the United States.
Types
Age-related macular degeneration always starts as the "dry" form, but can progress to the more severe "wet" form, according to the National Eye Institute, or NEI. More than 85 percent of macular degeneration is the dry form, according to NEI. The wet form causes additional damage on top of the lesions associated with the dry form.
Physiology
In macular degeneration, the problem begins when aging retinal cells fail to efficiently clear the waste proteins generated by the rods and cones of the macula. As the waste proteins accumulate, the macula becomes discolored, and fatty deposits called drusen form. The combination of waste proteins and drusen gradually rob the eye of clear central vision. In wet macular degeneration, in addition to these changes, abnormal new blood vessels grow under the macula, displacing and damaging it.
Drusen
Drusen appear as yellow, fatty-looking deposits under the rods and cones of the macula, according to the Mayo Clinic. The NEI says that drusen alone do not cause loss of vision. Drusen can be considered a sign of the severity of macular degeneration, rather than its cause.
Stages
Macular degeneration typically affects people over the age of 50, according to the Mayo Clinic. The National Eye Institute says that the lesions are not painful, and that the loss of vision can occur so slowly that some patients do not notice until they are at an advanced stage. Although macular degeneration begins in one eye, usually both eyes lose central vision over time, says the Mayo Clinic. Patients with dry macular degeneration pass through stages: an early stage with small drusen and no loss of vision; an intermediate stage with many medium-sized drusen and the beginnings of blurred central vision; and an advanced stage with large drusen and obvious blurring of central vision. The wet form of macular degeneration is always considered advanced, says the NEI.
Treatment
The NEI found that a dietary supplement called AREDs, containing high levels of anti-oxidants and zinc, can slow the development of lesions in patients with intermediate-stage dry macular degeneration, but do not reverse any loss of vision already incurred. It is not clear how this formulation slows the growth of the macular lesions. For wet macular degeneration, treatments aim to stop the formation or leakage of the abnormal blood vessels under the macula, slowing the progression of the lesions. Treatment options include injections of growth inhibitors into the eye, and laser surgery or photodynamic treatment to ablate the abnormal blood vessels.
