Macular degeneration (or age-related macular degeneration, abbreviated AMD) is the leading cause of vision loss in the Western world. The disease affects the retina, the light-sensitive layer of tissue at the back of the eye. This layer has photo-receptors that are stimulated by light and send signals to your brain, thereby generating vision. Specifically, AMD affects the central part of the retina called the macula and this is the portion of your eye that is used when engaging in visual activities that require the finest acuities, such as reading and driving. Macular degeneration occurs in either a dry (atrophic) or wet (exudative) form. In either case, the disease only affects the central vision, typically near the macula, and rarely causes total vision loss.
The majority of patients (over 80% of AMD cases) have the dry or atrophic type of macular degeneration. In this form of the disease, the slow deterioration of the retina is coincidental with the formation of small yellow deposits, known as drusen, in the macular region. This accumulation of drusen leads to a thinning of the macular tissues, causing distortions in vision that initially appear as wavelike. The eventual amount of central vision loss is directly related to the location and amount of retinal thinning caused by the drusen.
The exudative, or wet form of the disease, is far less common (about 20% of AMD cases), but it is more aggressive and threatening to one's vision. In the wet type of macular degeneration, abnormal blood vessels grow under the retina and macula through a process called neovascularization. These new blood vessels may bleed and leak fluid, thereby causing the macula to bulge or lift up, distorting or destroying central vision. In these circumstances, vision loss may be rapid and severe.
Although much research is being done on finding treatments for macular degeneration, no current treatment exists for the more common dry form, and the treatment for the wet form sometimes does not meet patients expectations. So, for many AMD patients, the use of low vision aids for macular degeneration is of great help and allows them to enhance their quality of life and remain independent.