Types and Definition

When light-sensing cells in the central region of the retina, called the macula, begin to breakdown and eventually die, it is called macular degeneration (MD).  Though there are different diseases, causes and types of this malfunction, the end result is the decline and loss of central vision, while peripheral vision remains intact.  For the most part, MD occurs in people over 60, although juvenile MD can occur in childhood and teen years.  There are several different types of juvenile diabetes, all of which seem to be associated with gene mutations, although exact causes are unknown.

Age Related Macular Degeneration

Age related MD (AMD), the more common form that is the leading cause of blindness in individuals over the age of 55, is generally linked to age and environmental factors, although recent research suggests a genetic component as a possible contributory source.  The most common form of AMD is called "dry" AMD, which accounts for about 90% of all cases.  In this form, a yellowish, fatty substance, called drusen, develops on the macula.  Though drusen can sometimes be present without vision loss, it is believed that it interferes with the function of the macula, and causes cells to deteriorate.

The other form, called "wet" AMD, sometimes develops as an advanced form of "dry" AMD.  With "wet" AMD, abnormal blood vessels form beneath the macula and leak fluid into the retina, causing severe vision loss.  Although this is the more rare form of AMD, it comprises about 90% of all cases of legal blindness due to AMD.

Symptoms

Some signs that may suggest MD include:

• Blurry central vision
• Distorted shapes and lines
• Spotty vision
• Difficulty seeing color

Diagnosis

Like other eye diseases, you should get checked regularly for MD, especially if you are over the age of 55, and have a family history of AMD.  In addition to visual acuity and color tests, your optometrist will use what is called the Amsler Grid Test, which will check for spots of sight loss and distorted vision.

Treatment

There is, at present, only one procedure available for the treatment of AMD, however there are several drugs that are currently undergoing FDA clinical trials, and are available to qualified patients.  Many eye care specialists recommend attention to healthy living, including a low fat/low cal diet with hi levels of vitamins E and C and lutein, an antioxidant found in green leafy vegetables, UV protective eyewear, and avoiding cigarette smoke, to help reduce risks.

Certain types of "wet" AMD can be treated with laser photocoagulation, which uses the heat from a laser to coagulate cells at the leakage point.  This is the only technique that has been proven effective for the treatment of any macular degeneration, but is limited to patients with a specific form of "wet" AMD, is effective only about half of the time, and the results tend to last no longer than a year.  

On the Horizon

In August of 2004, results from phase III clinical trial for the drug Macugen were submitted to the FDA for approval.  Macugen has the ability to block the protein that causes blood vessel growth, and can slow or stop the growth of "wet" AMD.  If approved, Macugen could be commercially available by the beginning of 2005, and could potentially provide benefits to all patients with "wet" AMD.  Still in various stages of clinical trials are drugs to halt the advancement of both "wet" and "dry" AMD, although many are still far from commercial availability.