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Definition
Age-related macular degeneration (AMD) is a common condition affecting people age 50 years and older. The condition may be associated with central vision loss such as loss of the ability to read, to drive a car, or see someone’s face if it progresses to more advanced stages.
The macula refers to the central portion of the retina. The retina is similar to film inside a camera. The image one sees is focused by the cornea and lens of the eye and then cast upon the center of the retina (macula.) Many people with AMD have no visual symptoms and may retain normal 20/20 vision indefinitely. A relatively small percentage of people with AMD will lose central vision and the ability to read and drive a car. Although AMD can cause central vision loss, it does not typically lead to complete blindness.
Types of AMD
There are two major types of AMD, a “dry” (non-neovascular) and a “wet” (neovascular) form. The dry form is the early stage. It is the most common form of AMD. There is usually little or no vision loss during this stage although there are exceptions with some people having significant vision loss from more advanced “dry” degeneration. The wet form is a late stage of the condition and affects about 10 percent of all people with the condition.
Dry AMD
The dry form of AMD is characterized by drusen. These are little yellow deposits that the doctor sees when looking at the macula on clinical examination. Drusen are the hallmark of AMD. Most people with drusen alone do not have significant visual changes or vision loss. A minority of people with dry AMD will advance to central vision loss due to geographic atrophy which is the loss of pigment layer under the macula. Unfortunately, there is no treatment or cure for geographic atrophy and the associated vision loss.
Wet AMD
Wet AMD accounts for the majority of central vision loss due to AMD. The wet type implies leakage and bleeding in the macula due to abnormal blood vessels known as choroidal neovascularization. These abnormal blood vessels start to grow beneath the center of the macula and, as they grow, they leak fluid or blood and cause central vision loss with blurring and distortion of vision. Untreated, these abnormal blood vessels typically will grow relatively large and eventually cause scarring with permanent and often severe central vision loss. New treatments are in evolution for wet AMD and these treatments aim to halt the growth and leakiness of choroidal neovascularization. Injection therapies or laser therapies are the mainstays of treatment of wet AMD.
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