Age-related macular degeneration is a degenerative disease affecting the center part of the retina known as the macula. The macula, which is described in more detail in macula, is the center part of the retina that is responsible for central vision. Central vision is what is used to perform activities requiring visual detail such as reading, recognizing faces, or driving a car. Macular degeneration is the leading cause of visual loss in patients over 50 years of age in the United States.
Age-related macular degeneration is often classified as one of two types. The first type, known as dry macular degeneration, involves gradual breakdown of the macula. It is characterized by certain findings, including drusen, which are yellow-white spots in the macula and outside of the macula, as well as degenerative changes in several layers of the macula. These changes may involve atrophy (loss of tissue) or hyperpigmentation (clumping of pigment cells). These changes may be mild and may result in few or no symptoms. With advanced disease, these changes may become more prevalent and may result in mild, moderate, or significant visual loss.
In the most advanced stages of dry macular degeneration, you can actually experience complete loss of critical layers of the retina, known as geo-graphic atrophy. When geographic atrophy involves the center of the macula, it results in severe visual loss. Fortunately, geographic atrophy occurs in only a minority of patients. Wet macular degeneration occurs when an abnormal growth of blood vessels underneath or into the macula results in leakage or bleeding. As you would imagine, leakage or bleeding in the retina often leads to significant visual symptoms and can result in sudden and dramatic loss of central vision.
At this time, vitamin supplementation offers the only approved treatment for dry macular degeneration, and it is geared toward preventing or slowing progression of disease. Fortunately, significant advances have occurred in the treatment of wet macular degeneration, as will be discussed in depth later in the book. It should be noted that all cases of wet macular degeneration originate from dry macular degeneration; how-ever, the majority of patients who have dry macular degeneration will not progress to wet disease. Approximately 10% of patients with dry macular degeneration will develop the wet form of the disease.