Macular degeneration is damage or breakdown of the macula. The macula is a small area at the back of the eye that allows us to see fine details clearly. When the macula doesn't function correctly, we experience blurriness or darkness in the center of our vision. Macular degeneration affects both distance and close vision and can make some activities - like threading a needle or reading - difficult or impossible.
Although macular degeneration reduces vision in the central part of the retina, it does not affect the eye's side or peripheral vision. For example, you could see the outline of a clock but not be able to tell what time it is. Macular degeneration alone does not result in total blindness. People continue to have some useful vision and are able to take care of themselves.
Many older people develop macular degeneration as part of the body's natural aging process. The two most common types of age-related macular degeneration are "dry" (atrophic) and "wet" (exudative.)
"Dry" macular degeneration: Most people have dry macular degeneration. It is caused by aging and the thinning of the tissues of the macula. Vision loss is usually gradual.
"Wet" macular degeneration: Wet macular degeneration accounts for about 10% of all cases. It results when abnormal blood vessels form at the back of the eye. These new blood vessels leak fluid or blood and blur central vision. Vision loss may be rapid and severe.
Macular degeneration can cause different symptoms in different people. The condition may be hardly noticeable in its early stages. Sometimes only one eye loses vision while the other eye continues to see well for many years. When both eyes are affected, the loss of central vision may be noticed more quickly.
The following are some common ways that vision loss is detected:
- Words on a page look blurred
- A dark or empty area appears in the center of vision
- Straight lines look distorted as in the following diagram
Many people do not realize that they have a macular problem until blurred vision becomes obvious. Your ophthalmologist can detect early stages of macular degeneration during a medical eye examination that includes the following:
- Viewing the macula with an ophthalmoscope
- A simple vision test where you look at a grid resembling graph paper
- Sometimes special photographs called angiograms are taken to find abnormal blood vessels under the retina. Fluorescent dye is injected into your arm and your eye is photographed as the dye passes through the blood vessels in the back of the eye.
Once abnormal blood vessels form, several treatments are available. However, patients do better if we catch the vessels in the early stages of the disease. This is why people with macular degeneration are asked to check their maculas by doing Amsler grid testing separately in each eye every day.
The first proven treatment involves burning the abnormal blood vessels with a conventional laser. It however, causes a permanent dark spot and the blood vessels often come back even after successful treatment. Nonetheless, this treatment is still used when we can easily define the blood vessels and they are a certain distance away from the very center.
A newer treatment for patients with wet macular degeneration and well defined abnormal blood vessels involves injecting the patient with a medicine called Visudyne and then applying a low intensity "cold laser" to the area. The blood vessels tend to recur, so patients are evaluated every 3 months. Most patients stabilize after 4 to 6 treatments done over 1 to 1 1/2 years.
Several experimental treatments are currently being evaluated in controlled national studies, including new laser treatments and the use of medications. Hopefully, in the future, some of these experimental techniques will become available and other options will also allow us to better treat this very common and devastating disease.