BACKGROUND: Macular degeneration, or age-related macular degeneration (AMD), is the leading cause of blindness in the United States for those age 60 and older. There are more than 10 million people in the United States suffering from AMD. It is caused by the deterioration of the central portion of the retina, the back part of our eye that records the images we see and sends them back to the brain through the optic nerve. The macula, the central portion of the retina that is effected by AMD, is responsible for focusing central vision, controlling our ability to read, drive a car, recognize faces or colors and see objects in fine detail.

There are two types of AMD: wet macular degeneration and dry macular degeneration. Wet macular degeneration is the more severe of the two types, affecting 10 percent to 15 percent of all AMD patients, but accounting for about 85 percent of AMD-related vision loss. In wet AMD, blood vessels grow under and through the retina and macula. They may then bleed and leak fluid, distorting or destroying central vision. With wet AMD, vision loss may be rapid and severe. With dry AMD, no such fluid leakage occurs. However, the formation of small yellow deposits under the macula leads to the thinning and drying out of the macula, causing it to lose its function. The amount and severity of central vision loss is directly related to the location and amount of retinal thinning.

TESTING NEW DROPS FOR AMD: Doctors at the Methodist Hospital in Houston, Texas are testing two new eye drops, one to treat wet AMD and the other to treat dry AMD. Researchers say they hope data from clinical trials will reveal whether the drops are effective within the next two years.

•Wet AMD drops: The traditional treatment for wet AMD is a series of injections into the effected eye or eyes. Side effects of these injections include serious eye infections that may include eye pain, light sensitivity and vision changes, retinal detachment and increased eye pressure. The topical drug called TG100801, still in phase II clinical trials, is designed to block new blood vessel growth and leakiness. It is also designed to reduce inflammation.

•Dry AMD drops: Hydergine is currently being tested on patients with dry AMD. Researchers say it is an antioxidant -- similar to a vitamin -- that prevents oxidative stress -- environmental effects that doctors believe age retinal cells. Drops are administered three to four times a day.

SYMPTOMS OF AMD: In its early stages, when the disease is the most preventable, AMD causes no symptoms. This is why the American Academy of Ophthalmology recommends an annual eye exam starting at age 60 to check for AMD. When the disease begins to progress, patients may notice fuzzy or blurry vision in one or both eyes, an empty or dark area in the center of their vision, and a dimming of vision while reading.