(modified from Canadian Ophthalmic Society   Website)
Macular degeneration is a leading cause of adult blindness   in Canada, accounting for one-third of all cases of vision loss. Most people   with the condition have a mild form. The most common form of macular   degeneration occurs in people over age 55 years and is known as age-related   macular degeneration.
Anatomy  At the back of the eye there is a thin layer of   light-sensitive nerve cells and fibres called the retina. We see things   because light entering the eye strikes the retina and is turned into an   electric impulse that the brain understands as an image.
Near   the centre of the retina is a small spot about the size of a pea called the   macula. The macula processes the details in the central part of the image   that the brain receives. The macula needs good light to work efficiently and   works best in daylight.  The   rest of the retina is responsible for side, or peripheral, vision. It is   especially sensitive to dim light, which makes night vision possible.
What is Macular Degeneration?  If the macula   deteriorates for some reason, the retina becomes like a camera with a spot on   the film. The centre of the field of vision blurs, and all detail is lost.   This condition is called macular degeneration.
There   are two types of macular degeneration. In the DRY type there is gradual   degeneration of the tissue cells that make up the macula, and symptoms tend   to develop over many months or years. In the more severe WET type, leakage   and often bleeding (hemorrhage) occur under the macula, causing the symptoms   to develop over a relatively short period.
As   an analogy, imagine that in order to see you need a healthy, weed-free, lawn   of grass.  With dry macular   degeneration there are a lot of bald spots in the lawn.  With wet macular degeneration there are   bald spots and unwanted weeds have grown through them.
Causes and Symptoms  Although the specific cause of the deterioration is not   completely understood, age-related macular degeneration seems to be part of   the aging process. As the eye gets older, the membrane separating the macula   from the retinal blood vessels that supply it may break down. At the same   time, new, abnormal blood vessels form that may bleed and displace the   macula. Cut off from its source of nourishment, the macula is permanently   damaged.
Although   macular degeneration is usually associated with aging, it may be linked to   other conditions, such as smoking, high blood pressure, arteriosclerosis and   general diseases like diabetes mellitus. Children and adolescents may be   affected by hereditary macular degeneration. Myopia, or near-sightedness, is   a contributing factor, and excessive light and eye injuries leading to   retinal detachment may also damage the macula.
The   course of the condition may be slow or rapid, but the deterioration generally   occurs over a period of a few years. Peripheral vision will remain normal,   but the person will have difficulty seeing at a distance or doing detailed   work. Faces may begin to blur, and it becomes harder to distinguish colours.   Distortion or wavy lines may accompany or precede the blurred vision.  For this reason, your doctor may ask you   to look at a graph paper grid (Amsler grid) with each eye singly once a day   or once a week.
Treatment   begins with an eye examination to try to determine the cause of the   condition. Unfortunately, because so little is known about the direct cause   of macular degeneration, effective treatment is not possible in all cases.
Dietary   supplements (vitamins, zinc) may be of some help in slowing down the   progression of macular degneration.    Eating a good, normal diet with broccoli and collard greens may be   just as helpful. 
Lasers   are sometimes used to seal damaged blood vessels in the early stages of the   wet type of macular degeneration. To determine whether laser treatment can  help, a test called fluorescein angiography may be necessary. This test,   which involves injecting a dye into a vein and then photographing the   circulation of the dye, is ordered by an ophthalmologist-a medically trained   eye doctor-and is usually performed in a hospital.
We   still have no "magic bullet" against macular degeneration.  Many therapies are initially introduced   with much fanfare (e.g. interferon, thalidomide, radiation) but later are   shown to be not that effective. 
Visudyne   is a relatively newer therapy that offers some hope in treating your  disease.  Macular translocation   (rotation of the retina) should probably be still regarded as an experimental  procedure.  Electronic retinal   transplants are still in their infancy.
Although   macular degeneration cannot be reversed, people with the condition can   usually continue their daily activities using their peripheral vision and   making the best use of their remaining central (detail) vision. Devices such   as high-intensity reading lamps and magnifiers help compensate for the loss   of detail and make some fine work possible again. People with macular  degeneration almost never go completely blind - they maintain their side   vision.