(the following is taken from the website of the Macular Degeneration Foundation- www.eyesite.org)
What is macular degeneration?
In macular degeneration, the light-sensing cells of the macula mysteriously malfunction and may over time cease to work. Macular degeneration occurs most often in people over 60 years old, in which case it is called Age Related Macular Degeneration (ARMD). Much less common are several hereditary forms of macular degeneration, which usually affect children or teen-agers. Collectively, they are called Juvenile Macular Degeneration. They include Best’s Disease, Stargardt’s Disease, Sorsby’s Disease and some others.
How is macular degeneration diagnosed?
The major symptoms of macular degeneration are:
1) When viewing an Amsler grid, some straight lines appear wavy, and some patches of the grid appear blank.
2) When visual acuity is measured with a Snellen chart, visual acuity has typically declined by at least 2 lines (e.g. 20/20 -> 20/80) if macular degeneration has occurred.
3) In dry macular degeneration, drusen spots are evident in fundus photographs (i.e. photographs of the retina).
4) In wet macular degeneration, when angiography is performed, leakage of the indicator dye into the bloodstream is seen from blood vessels behind the macula.
5) When an electroretinogram is performed, the electrical signal obtained when a point in the macula is illuminated, is weaker or absent compared to a normal eye.
6) Visual acuity and color sensitivity are similar for the three primary colors, red, green and blue.
What are dry and wet macular degeneration?
About 85 – 90% of ARMD cases are the dry, or atrophic, form, in which yellowish spots of fatty deposits called drusen appear on the macula. The rest of ARMD cases are the wet form, so called because of leakage into the retina from newly forming blood vessels in the choroid, a part of the eye behind the retina. Normally, blood vessels in the choroid bring nutrients to, and carry waste products away from, the retina. Sometimes the fine blood vessels in the choroid underlying the macula begin to proliferate, a process called choroidal neovascularization, or CNV. The cause is unknown. When those blood vessels proliferate, they leak, and cells in the macula are damaged and killed. The principal symptom of macular degeneration is reduction or loss of central vision, with retention of peripheral vision.
Early detection of changes from dry to wet is the key to effective treatment.