Macular degeneration

Alternative names

Definition

Causes, incidence, and risk factors

The macula is the part of the retina that allows the eye to see fine details at the center of the field of vision. Degeneration results from a partial breakdown of the retinal pigment epithelium (RPE).

The RPE is the insulating layer between the retina and the choroid (the layer of blood vessels behind the retina). The RPE acts as a selective filter to determine what nutrients reach the retina from the choroid. Many components of blood are harmful to the retina and are kept away from the retina by normal RPE.

Breakdown of the RPE interferes with the metabolism of the retina, causing thinning of the retina (the "dry" phase of macular degeneration). These harmful elements may also promote new blood vessel formation and fluid leakage (the "wet" phase of macular degeneration).

This disorder results in the loss of central vision only -- peripheral fields are always maintained. Although loss of ability to read and drive may be caused by macular degeneration, the disease does not lead to complete blindness.

The disease becomes increasingly common amongst people in each succeeding decade over 50. By age 75, almost 15% of people have this condition. Other risk factors are family history, cigarette smoking, and being Caucasian.

Symptoms

• Blurred, distorted, dim, or absent central vision

Signs and tests

Tests to evaluate the retina may include:

• Visual acuity
• Refraction test
• Pupillary reflex response
• Slit lamp examination
• Retinal examination by various techniques
• Retinal photography
• Fluorescein angiography , and sometimes indocyanine green angiography
• Amsler grid

Treatment

There is no specific treatment for "dry" macular degeneration, although zinc supplementation may slow the progression of the disease (see zinc in diet).

For the "wet" form of macular degeneration, laser photocoagulation ( laser surgery to coagulate leaking choroidal blood vessels) may be useful in the early stages of the wet form of the disease. It involves the use of a thermal laser, which burns the abnormal, leaky blood vessels and stops them from spreading.

A newer treatment option for patients with "wet" macular degeneration is photodynamic therapy, which can be performed in a doctor's office. In this procedure a light-sensitive medication called Visudyne (verteporfin) is injected into a vein in the patient's arm. The drug circulates through the body to the eyes.

When a non-thermal laser is shone into the eyes, Visudyne produces a chemical reaction that destroys abnormal blood vessels. If the vessels re-grow, the procedure can be repeated.

Photodynamic therapy is expensive and is not curative, but it can be successful in managing a particular area of leakage from the choroid through the RPE.

Your physician may recommend that you use an Amsler grid to discover possible new leaks before scarring occurs.

Low-vision aids and therapy can be vital to improvement of quality of vision and life.

Support Groups

Expectations (prognosis)

Most people with mild dry macular degeneration will never have disabling central vision loss. However, there is no way to predict who will progress to a more severe form of the disease. This disorder results in the loss of central vision only -- macular degeneration cannot cause peripheral vision loss.

The wet form of macular degeneration often leads to significant vision loss.

Complications

Loss of central vision may interfere with many activities of daily living. Reading may require magnification or may become impossible. The ability to drive may be lost.

Calling your health care provider

Call your health care provider if you notice any dim or distorted areas in your vision. Routine dilated eye exams can monitor for the condition.

Prevention

There is no known effective prevention. If you have a family history of macular degeneration, avoid all use of tobacco.

Update Date: 8/26/2002