Age-related macular degeneration or AMD is a degenerative condition of the macula (the central retina). It is the most common cause of vision loss in the United States in those 50 or older, and its prevalence increases with age. AMD is caused by hardening of the arteries that nourish the retina. This deprives the sensitive retinal tissue of oxygen and nutrients that it needs to function and thrive. As a result, the central vision deteriorates.
Macular degeneration varies widely in severity. In the worst cases, it causes a complete loss of central vision, making reading or driving impossible. For others, it may only cause slight distortion. Fortunately, macular degeneration does not cause total blindness since it does not affect the peripheral vision.
AMD is classified as either wet (neovascular) or dry (non-neovascular).
About 10% of patients who suffer from macular degeneration have wet AMD. This type occurs when new vessels form to improve the blood supply to oxygen-deprived retinal tissue. However, the new vessels are very delicate and break easily, causing bleeding and damage to surrounding tissue. Patient with wet macular degeneration develop new blood vessels under the retina. This causes hemorrhage, swelling, and scar tissue but it can be treated with laser in some cases.
Dry macular degeneration, although more common, typically results in a less severe, more gradual loss of vision.
The dry type is much more common and is characterized by drusen and loss of pigment in the retina. Drusen are small, yellowish deposits that form within the layers of the retina.
Eye physicians usually diagnose AMD. Vision testing, Amsler grid test, ophthalmoscopy, fundus photography, fluorescein angiography, indocyanine angiography and optical coherence tomography (OCT) are some common tests performed during a retinal exam.