Age-related macular degeneration (AMD) strikes at the macula, the heart of the eye's vision center. This small part of the retina is responsible for sharp, central vision. People with AMD often develop blurred or distorted vision and cannot clearly see objects directly in front of them. Eventually, they may develop a blind spot in the middle of their field of vision that increases in size as the disease progresses. There are two types of AMD: dry and wet.
Most people with AMD have the dry version. It is caused by a breakdown or thinning of the retina. Although symptoms vary, people with dry AMD usually first experience blurred vision and difficulty reading or distinguishing faces. In some people, dry AMD progresses to the more serious wet form, which can lead to severe vision loss. It occurs when abnormal blood vessels develop in the layer of cells beneath the retina. When they leak blood or fluid into the retina (hence "wet"), they can cause scarring in the macula, leading to a blind spot at the center of the visual field. Over time, this area may enlarge.
Your doctor can often detect signs of age-related macular degeneration before sight is affected and before permanent vision loss occurs. She or he may suspect this condition if the view through an ophthalmoscope reveals clumps of pigment or clusters of drusen (small yellow deposits that build up under the macula).
An Amsler grid test can also help to identify the distorted vision typical of AMD. For this test, you focus your eyes on a central dot on a grid that resembles graph paper. If the lines near the dot appear wavy or are missing, the wet form of AMD may be to blame.
Routine eye exams and early detection are important. The earlier AMD is detected, the more likely it can be treated successfully.
For more information on diagnosing and treating AMD, buy The Aging Eye, a Special Health Report from Harvard Medical School.