Macular Degeneration

The macula is a very small area in the center of the retina. In size, the macula is about the same size as a capital "0" in the type on this page. This small area is for our central or "straight ahead" vision used for reading and other fine tasks.

If the macula is damaged, both distance and close up vision will begin to fade.  The central vision is blurred, even though the images around the blurred area may be clearly visible. Since the eye still sees images to the side or "peripherally", macular degeneration does not result in total blindness. However, daily activities such as driving, reading, and fine-detailed close work become progressively more difficult, if not altogether impossible.   Strong magnifying glasses or special low vision optical aids can be useful.

WET and DRY MACULAR DEGENERATION
The two types of AMD are “dry” and “wet.”

Dry macular degeneration, sometimes called involutional macular degeneration, is the most common form of macular degeneration and accounts for up to 90% of all cases. This form is caused by breakdown or thinning of the tissues in the macula and is associated with aging.  A common early indication of AMD risk is the presence of drusen.  Drusen are yellow deposits that can accumulate in the retina; as drusen increase in size or number, the risk of vision loss increases.

Wet macular degeneration, also known as exudative macular degeneration, accounts for about 10% of all AMD cases. Normally the macula is protected by a thin tissue that separates it from the very fine blood vessels nourishing the back of the eye. Sometimes these vessels break or leak and cause scar tissue to form. This often leads to the growth of new abnormal blood vessels in the scar tissue. These newly formed vessels are especially fragile. They rupture easily and may leak. Blood and fluid leaking destroy the light-sensitive photoreceptor cells in the macula and cause further scarring, which can lead to sudden rapid vision loss.  The vision becomes distorted and blurred, and dense scar tissue blocks out central vision to a severe degree.

Some other types of macular degeneration are inherited, may occur in juveniles and are not associated with the aging process.  Occasionally, injury, inflammation or infection may damage the delicate tissue of the macula.

SYMPTOMS: Macular degeneration can cause different symptoms in different people. Macular degeneration often involves one eye at a time, so may hardly be noticeable in the beginning stages, particularly if the other eye is normal. Sometimes one loses vision while the other eye continues to see well for many years.  If both eyes are affected, it can become very difficult to recognize faces and read. 
 In general, the most common symptoms are:

1.     Color vision may become altered.
2.     Words on a page look blurred.
3.     Straight lines look distorted.
4.     Dark or empty areas appear in the center of vision.

DETECTION AND DIAGNOSIS: Many patients do not realize they have a macular problem until blurred vision becomes obvious.  Your eye doctor can detect macular degeneration in the early stages by careful examination of the retina using dilation drops.

A few more tests will usually be included in the examination, such as a color vision test, an Amsler grid test, and special visual field testing.  A special imaging device called optical coherence tomography (OCT) may also be used.  The OCT can provide your doctor with detailed cross-section images of the retina to aid in managing your macular degeneration for subtle changes.  Sometimes a fluorescein angiogram is done. An angiogram is a series of special photographs taken after a dye is injected into the patient's arm. The dye helps to clarify any blood vessel abnormality that may be present.

If you are over age 50, or if other members of your family have a history of retinal problems, routine eye examinations may detect macular degeneration in the early stages.  Early detection and subsequent treatment, if appropriate, may prevent further loss of vision.

MEDICAL AND SURGICAL TREATMENT: There is no cure for the most common form of dry macular degeneration. However, preventive therapies can help slow or stop the progression in some individuals.  There are a variety of treatment options currently being used to decrease vision loss associated with the wet, or exudative, form of macular degeneration. 

In the past, conventional laser treatment has been used to retard or slow the spread of new blood vessel growth.  In this treatment, a focused intense beam of laser light is used to seal off leaking membranes and destroy new blood vessels. This reduces further loss of vision from progressive scarring of the macula and the surrounding retina.   The drawback is that the conventional laser also damages surrounding retinal tissues and therefore can only be applied to certain locations of leaking blood vessels. 

A more common treatment of wet macular degeneration is the technique known as photodynamic therapy (PDT). The concept of PDT is to selectively close the abnormal blood vessels, eliminating the leakage and bleeding, and stabilizing or improving the vision. This is done without the damaging effect of conventional laser on the normal structures of the retina and back of the eye.

There is also a new drug, called Macugen, that works by blocking vascular endothelial growth factor (VEGF), a protein that promotes blood vessel growth. Macugen has the potential for helping all patients with the wet form of the disease, whereas the currently approved treatment, photodynamic therapy, is only approved for patients that have a subtype of wet macular degeneration. Other anti-VEGF treatments are currently being studied and even being used in certain settings.  These medications are showing promising results for not only reducing further vision loss, but also improving vision in many cases.

Because early intervention and treatment is critical, preventive steps and regular medical eye exams are strongly recommended.

OPTICAL AIDS AND LIGHTING: Often people find their near vision improves through the use of low vision optical aids. Spectacles, hand or straight magnifiers, telescopes, and closed circuit television for viewing objects are some of the available resources. Aids are either prescribed by your eye doctor or by referral to a low vision specialist or center.

Bright light properly directed is often helpful for reading and close work. Special lamps can also be helpful. Books, newspapers and magazines in large print offer further help.