The leading cause of blindness in Americans over 60, AMD has two major forms: wet and dry.

Wet AMD is the result of abnormal blood vessels growing under the macula. These vessels are typically fragile and leak blood and fluid into the eye, which causes quick sight degeneration. The most common early effect is straight lines appear wavy.Dry AMD is the breakdown of cells in the macula and it makes up 85 percent of AMD cases. There are three stages: early, intermediate and advanced, which are determined by drusen, yellow spots on the retina, and how blurred their vision has become.

Information from the National Eye Institute, http://www.nei.nih.gov/index.asp