It takes an exceptionally steady hand and an unwavering focus to do complex surgery in an area the size of a dime. It also takes tiny instruments fashioned for a micro-environment and a precise vision of the work at hand.

This is the arena where Marco Zarbin, MD, wrestles with minuscule blood vessels and cellular transplants. And it is this surgical field where he hopes to make his greatest contribution to treating a disease called age-related macular degeneration (AMD).

AMD is a serious condition that can result in blindness. It's thought to affect 6 million Americans, and according to some estimates, will strike 20 million in the next 50 years. The incidence is definitely on the rise, says the chair of ophthalmology at UMDNJ-New Jersey Medical School (NJMS), who believes this is only partially a result of genetics and what sociologists call the aging of the population. The other factors, he asserts, are probably environmental, but no one knows what they are.

The macula is the region of the retina necessary to see detail. It is about as large as the head of a nail. In the center of the macula are special light-sensing cells, called photoreceptors, that work in tandem with a cell layer called the retinal pigment epithelium (RPE) to provide sharp vision. Tiny blood vessels called choriocapillaris provide the blood supply necessary for the photoreceptors and RPE to function optimally.

While a malfunction of the macula may not be noticeable in its earliest stages, it can produce disabling symptoms as it progresses: blurring of both distance and close vision, an inability to perceive color, a dark or empty area in the center of vision, and a distortion of straight lines. In AMD, central vision often progressively diminishes, but peripheral vision is usually not affected. Although the macula can degenerate at any age, even in childhood, the disease called age-related macular degeneration affects those 55 and over. Zarbin says that AMD infrequently causes total blindness, but it often leaves individuals unable to read, to recognize faces, to drive, watch TV and even to live independently.

There are actually two variants of AMD, the "dry" form and the "wet" form. (Both types can co-exist in the same eye.) The dry form is the more common - affecting about 80 percent of those with the condition - and is usually less disabling. Often, the first sign is drusen, yellow flecks or spots under the retina. These abnormal cellular deposits can exist without seeming to interfere with vision. In fact, hard drusen are fairly common in those under 55 and don't seem to predict the onset of AMD. But in those over 55, large, soft drusen are usually a sign of the disease. It is thought that eventually the photoreceptors and the RPE cells overlying the drusen die, causing the symptoms associated with the atrophic or dry form.

In the wet form, there is a build-up of drusen material, as well as the growth of fragile, new blood vessels called choroidal new vessels or CNVs. These blood vessels grow from the choriocapillaris and leak blood and fluid under the macula, which interfere with its function by distorting the normal shape of the retina, and sometimes, by forming scar tissue. It is the wet - or exudative - form that most often destroys central vision.

Interest in AMD - particularly the more destructive wet form - has grown astronomically in the last decade. And research efforts - based on a better understanding of the disease, new technologies and more sophisticated surgical instrumentation and techniques - are starting to pay off. Zarbin points out that a quick internet search for research articles on macular degeneration yielded only 164 for the years 1985 to 1990, but 424 for the years 1996 to 1999, an annualized fourfold increase.

Among the big questions being tackled by investigators is whether AMD can be prevented, or if its progress can be slowed down. Potential culprits under serious investigation as triggers for the disease include sun damage, and vitamin and mineral deficiencies. Although sun exposure has been clearly linked to some eye disorders, there is no evidence that sunlight plays a role in the onset or worsening of AMD. Sunglasses and broad-brimmed hats are still a good idea, but they probably don't provide protection against macular degeneration.