 |
| What Is Age-Related Macular Degeneration |
The first sign of AMD may be a need for more light when you do close-up work. Fine newsprint may become harder to read and street signs more difficult to recognize. Eventually you may notice that when you're looking at an object, what should be a smooth, straight line appears distorted or crooked. Gray or blank spots may mask the center of your visual field. The condition may progress rapidly, leading to severe vision loss in one or both eyes.
Macular degeneration affects your central vision but not peripheral vision; thus it does not cause total blindness. Still, the loss of clear central vision - critical for reading, driving, recognizing people's faces and doing detail work - greatly affects your quality of life. In most cases the damage caused by macular degeneration can't be reversed, but early detection may help reduce the extent of vision loss.
Types
There are two types of macular degeneration: dry macular degeneration and wet macular degeneration. To understand the differences between these two forms of the disease, it's also important to understand what they have in common. The macula is the center of your retina and is made up of densely packed light-sensitive cells called cones and rods. These cells, particularly the cones, are essential for central vision. The choroid is an underlying layer of blood vessels that nourishes the cones and rods of the retina. A layer of tissue forming the outermost surface of the retina is called the retinal pigment epithelium (RPE). The RPE is a critical passageway for nutrients from the choroid to the retina and helps remove waste products from the retina to the choroid.
As you age, the RPE may deteriorate and thin (a process known as atrophy), which sets off a chain of events. The nutritional and waste-removing cycles between the retina and the choroid are interrupted. Waste deposits begin to form. Lacking nutrients, the light-sensitive cells of the macula become damaged. The damaged cells can no longer send normal signals through the optic nerve to your brain, and your vision becomes blurred. This is often the first symptom of macular degeneration.
Dry macular degeneration
Most people with macular degeneration have the dry form. In fact, AMD always starts out as the dry form. Dry AMD may initially affect only one eye but, in most cases, both eyes eventually become involved.
Dry macular degeneration occurs when the RPE cells begin to thin. The normally uniform reddish color of the macula takes on a mottled appearance. Drusen, which look like yellow dots, appear under the retina.
Initially, in spite of these developments, you may notice little or no change in your vision. Many people who've received a diagnosis of early-stage dry macular degeneration may not be bothered with symptoms such as blurred eyesight until they live to a very old age. But as the drusen and mottled pigmentation continue to
develop, your vision may deteriorate sooner. Thinning of the RPE may progress to a point where this protective layer of the retina disappears. This affects the overlying cones and rods and may result in complete loss of your central vision.
Wet macular degeneration
The wet form of macular degeneration accounts for 10 percent to 15 percent of all cases, but it's responsible for nearly 90 percent of the severe vision loss that people with AMD experience. If you develop wet macular degeneration in one eye, your odds of getting it in the other eye increase greatly.
Wet macular degeneration develops when new blood vessels grow from the choroid underneath the macula. These vessels leak fluid or blood - hence it is called wet AMD - and cause your central vision to blur. All eyes with wet AMD also show signs of dry AMD, that is, drusen and mottled pigmentation of the retina. In addition, what should be straight lines in your sight become wavy or crooked, and blank spots appear in your field of vision. Sight loss is usually rapid and severe, resulting in legal blindness, defined as 20/200 vision or worse. This means that what someone with normal vision can see from 200 feet, a person with 20/200 vision can see only from 20 feet.
 |
| What Is Age-Related Macular Degeneration |
A comparatively rare form of wet macular degeneration is called retinal pigment epithelial detachment (PED). In this instance fluid leaks from the choroid although no abnormal blood vessels have started to grow there. The fluid collects under the retinal pigment epithelium, causing what looks like a blister or a bump under the macula. This kind of macular degeneration causes the same symptoms as wet AMD and frequently progresses to wet AMD with newly growing abnormal blood vessels. To find out more, you can check out What Is Age-Related Macular Degeneration.