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AGE-RELATED MACULAR DEGENERATION
An excerpt from the book Taking Care of Your Eyes.

Taking Care of Your EyesAge-related macular degeneration (AMD) is the leading cause of poor vision in people over 60. (It is sometimes found at younger ages, but that is rare.) When the macula is damaged (or degenerates, as from AMD), central vision is interfered with, so that when you look at an object straight on, part of it may seem distorted, blotted out, or shrouded in a dark haze.

The macula is a key part of the retina, the light-sensitive nerve tissue at the back of the eye that forms the "screen" upon which images are focused. Though the macular area is tiny, no larger than a pinhead, it contains all the cells needed for central vision - seeing straight ahead, seeing fine detail, and crisp color vision - in other words, the sharpest, most useful part of vision. AMD usually involves both eyes, though it may start in one eye and not affect the other eye until much later.

Most people with even advanced AMD do not lose all of their vision. No matter how poor central vision gets, your peripheral vision - the outer edge of your visual field, which does not depend on the macula - should stay useful. You should continue to be able to see off to the sides.

Types of AMD

There are two major forms of AMD, called "dry" and "wet." Most patients have the dry form, which tends to develop slowly as the tissue (pigment epithelium and visual cells) beneath the macula gradually deteriorates. With wet AMD, tissue deterioration is accompanied by tiny abnormal blood vessels called "subretinal neovascular membranes." These form under the retina and start to leak fluid or bleed. If the fluid or blood reaches the macula and lifts it out of position, vision becomes distorted and visual sharpness can be lost.

Symptoms

The typical first symptom (in either form) is blurring of vision. When the blurring is gradual, you may think you need new eyeglasses. But a new prescription is not likely to improve your vision because the problem is not with the optical parts of the eye. As time goes on, you may notice a hazy or dark zone in the center of objects you look at directly. Colors may begin to look different or lose richness. With wet AMD especially, straight lines, such as the edges of doorways, may start to look bent or crooked as vision becomes distorted and wavy.

Symptoms may may be gradual or sudden (suddenness is more likely with wet AMD). When the loss of vision is in one eye only, you can't always tell how long it has existed, since it is "hidden" when both eyes are used together. It may only become apparent when the good eye is covered.

Examination

Your vision will be checked and you will have a refraction (test for glasses) along with a complete eye exam. Your pupils will be dilated (enlarged) with eyedrops so that the insides of your eyes can be evaluated with an ophthalmoscope. A special type of contact lens may be used for examining both retinas and maculas under the high magnification of a slit lamp microscope.

Photographs may be taken of the retina, to determine the extent of the problem and evaluate its progression. You may also have a retinal "angiogram," retinal photographs that help identify the position and extent of any abnormal blood vessels or leakages. For this test, called fluorescein angiography (FA), an orange-colored dye (fluorescein) is injected into a vein in your arm and then a series of photographs is taken as the dye travels through the eye's blood vessels. If more information is needed, a dye called indocyanine green (ICG) may be used to make another type of angiogram. Angiograms provide important guidance for treatment.

Treatment

So far, there are no medications that have proven to be effective. But wet AMD -- in the early stages only -- can sometimes benefit from treatment with a surgical laser, to seal the leaks or destroy the abnormal blood vessels under the macula. (The laser cannot help the dry type of AMD, or even most stages of the wet type.) The goal of laser treatment is to prevent further leadage and stabilize vision. Only occasionally does vision improve. Please don't expect miracles; the laser treatment may not help at all and vision may even get worse.

What To Expect

AMD usually develops gradually or in small spurts over many months, then slows down or stops. Both eyes will probably be affected, though one eye may precede the other by a long time, even years. Wet changes occur unpredictably; they may even develop in AMD that started as the dry type, or they may recur in previously treated wet AMD.

It is possible, even with no laser treatment, for the degenerative process to stop before very much vision has been lost. But it is more likely that central vision will continue decreasing, probably to the point that reading is hampered and driving a car is no longer safe.

What You Can Do

In addition to having regular eye exams, there is an easy and important test you can do yourself. Take a few seconds every day to check your vision with an Amsler grid, a card printed with a pattern of crossing lines that form small squares.

Test each eye separately, with the other eye covered. The lines should look straight and solid. If any lines suddenly start looking wavy or having missing segments, that could indicate the beginning of wet changes that might be treatable, and you should make an appointment to have your eyes checked right away.

Always keep in mind that using your eyes will never harm them. You can continue any of your usual activities as long as you feel comfortable doing them. Even with reduced vision, your life can be surprisingly normal and fulfilling.

 

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