As the eye looks straight ahead, the macula is the point of the retina where light rays meet as they are focused by the cornea and the lens of the eye. Similar to the film in a camera, the retina receives images that come through this "camera-like" lens. If the macula is damaged, central part of the images are blocked, as if a blurred area had been placed in the center of the picture. The images around the blurred area may be clearly visible.
Macular degeneration is damage or breakdown of the macula. The eye still sees objects to the side, since side (peripheral vision) is usually not affected. For this reason, macular degeneration alone does not result in total blindness. However, it can make reading or close work difficult or impossible without the use of special low vision optical aids.
Although macular degeneration most occurs in older people, aging alone does not always result in central visual loss. Nevertheless, macular degeneration is the leading cause of impairment of reading and fine or close-up vision in the United States.
The most common form of macular degeneration is involutional macular degeneration. This accounts for 70 percent of all cases and is associated with aging. It is caused by a breakdown or thinning of the tissues in the macula.
About 10 percent of all macular degeneration falls into a category called exudative macular degeneration. Normally, the macula is protected by a thin tissue that separates it from the fine blood vessels that nourish the back of the eye. Sometimes, these blood 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 leaking fluid destroy the macula and cause further scarring. Vision becomes distorted and blurred, and dense scar tissue blocks out central vision to a severe degree.
Macular degeneration can be inherited. I can also occur in juveniles (juvenile macular degeneration) and may not necessarily be associated with the aging process. Occasionally, injury, infection or inflammation can also damage the delicate tissue of the macula.
If only one eye is affected, macular degeneration is hardly noticeable in the beginning stages, particularly when the other eye is normal. This condition often involves one eye at a time, so it may be some time before a patient notices visual problems.
Macular degeneration can cause different symptoms in different people. Sometimes, only one eye loses vision, while the other eye continues to see well for many years. If both eyes are affected, however, reading and close-up work may become extremely difficult.
Macular degeneration alone does not cause total blindness. Since side vision is usually unaffected, most people can continue on with their lives quite well.
Many patients do not realize they have a macular problem until blurred vision becomes obvious. An ophthalmologist (eye doctor) can detect macular degeneration in the early stages. The ophthalmologist examines the macula carefully by viewing it with an instrument called an opthalmoscope, to see if damage is present.
The examination will usually include a few more tests:
- A grid test, in which the patient looks at a test page (similar to graph paper), will be used to check the extent of vision loss.
- A color vision test will show if a patient can tell color differences, and additional tests will help to discover conditions that may be causing the macula to deteriorate.
- Sometimes a fluorescent angiogram is done. The ophthalmologist injects a dye into the patient's arm, and then takes photos of the retina and macula. The dye helps to clarify any blood vessel abnormality that might be present.
Macular degeneration can be detected and diagnosed early by an ophthalmologist if periodic eye examinations are part of your health care. Early detection is important, since people may not realize their vision is impaired. Having your eyes checked is especially appropriate if other family members have a history of retinal problems. For patients with macular degeneration, early diagnosis by an ophthalmologist may prevent further damage or aid the individual in making a visual adjustment with low vision aids.
Some patients may benefit from carefully-prescribed low vision aids.
In some patients, early detection can prevent severe vision loss with argon laser treatment. Laser therapy is increasingly used for more patients with the severe, leaky form of age-related macular degeneration. This relatively low-energy laser heats rather than vaporizes tissues, acting essentially like a welder. The green beams of the argon laser are only absorbed by red objects, so it selectively heats up and seals blood vessels (because they contain red blood cells) and leaves most other parts of the eye undisturbed. The narrowness of the beam enhances laser precision, allowing the ophthalmologist to target only diseased blood vessels.
This type of surgery generally takes only a few minutes and may be done with the aid of a local anesthetic to prevent discomfort. Soon afterwards, the patient is able to return home and resume normal daily activities.
What other tests might be used to determine the cause of visual loss? What are the side effects or risks of the tests?
What is causing the macula to deteriorate?
Can further damage be prevented?
Could argon laser treatment be used to prevent further degeneration?
If yes, do you perform this procedure or will you recommend a specialist?
What are the possible complications of laser treatment?
After the laser treatment, are there any measures to be taken to prevent new problems or further deterioration?