The eye is like a camera. When you take a picture the lenses in the front of the camera allow light through and focus tha light on the film that covers the back inside wall of the camera. When the light hits the film, a picture is taken.

The eye works much the same way. The front parts of the eye (the cornea, the pupil, and the lens) are clear and allow light through. the cornea and lens focus that light on the back inside wall of the eye. A thin layer of tissue called the retina covers the back inside wall of the eye. The retina is like the film in a camera. It is the seeing tissue. When the focused light hits the retina, a picture is taken. Messages about this picture are sent to the brain through the optic nerve. This is how we see.

The retina has two parts: the peripheral retina and the macula. If you imagine the retina as a circle with a bull's-eye at the center, the macula is like the bull's-eye: it is very small. It is located near the optic nerve. The large area of retina that surrounds the macula and makes up 95% of the retina is called the peripheral retina. The peripheral retina gives us vision to the side, this is called "peripheal" vision. This is what we refer to when we say, "I saw something out of the corner of my eye." Because the peripheral retina cannot see detail clearly, we cannot use peripheral vision to read, thread a needle, drive, or even recognize a face. If I see someone off to my side, "out of the corner of my eye," I can tell who the person is by his or her general shape, but I won't be able to see the expression on that person's face. In order to see fine detail, we must look straight ahead, using the macula, the bull's-eye center of the retina. Though the macula makes up only a small part of the retina, it is one hundred times more sensitive to detail than th peripheral retina. The macula allows us to see tiny detail, to read fine print, recognize faces, thread a needle, read the time, see street signs, see grains of salt being poured from a shaker, etc. The only way to see detail is by using your macula and it must be healthy to work properly.

Macular Degeneration

Macular degeneration is most often related to aging. There are some unusual types of macular degeneration that start very early in life, however, most patients with macular degeneration begin to notice problems with eyesight sometime after age 50. Macular degeneration may be hereditary and therefore may run in families.

Macular degeneration usually starts with the appearance of spots on the retina. These spots are called drusen (see figure 12). Drusen are like age spots and do not usually change vision very much themselves. Most patients with drusen never have a serious loss of vision and only a few develop severe macular degeneration with loss of vision. When macular degeneration does lead to loss of vision, that loss usually starts in just one eye and only later may affect the other eye. In some, it never affects the vision of the second eye. When a person loses vision from macular degeneration in one eye, the loss of vision may not even be noticed because the healthy eye can still see detail. In general, it is important to discover any chane in eyesight as early as possible because the chance that treatment will help is greatest in the early stages of any eye problem. That is why you should test the eyesight in each eye, each day, especially if your doctor has told you that you have drusen. If macular degeneration has affected the vision of only one macula, you will still be able to see detail (to read, to drive, to thread a needle) with the other, healthy macula. If is only when macular degeneration severely affects both eyes that it will become difficult, or perhaps impossible to do the kind of work that requires detail vision. A person with severe macular degeneration, who has lost the ability to see detail with each eye, rarely loses peripheral vision and will still be able to get along fairly well. It is very rare for someone with macular degeneration to lose both macular (detail) and peripheral (side) vision. Macular degeneration only very rarely causes total blindness. Almost all people with severe macular degeneration in each eye can see well enough to take care of themselves and continue those activities that do not require detail vision. People with macular degeneration in each eye usually learn to make use of the areas just outside the macula to see detail better. This ability to look slightly off center usually improves with time, although eyesight will never be as good as it wasbefore the macula was damaged. Once the macula has been severely damaged, treatment is usually no longer possible. For this reason everyone should test the vision in each eye, separately, each day.

The Symptoms of Macular Degeneration

In the earliest stages of macular degeneration, it may be a little harder to see. Vision may be blurred for distance or for reading, or both. A very frequent and important symptom is distortion. Straight lines will not look straight. A telephone pole or a door frame may seem a little bent, crooked, or irregular, as though seen through heat waves on a highway. An area of the Amsler grid will appear distorted and the small boxes in that area will vary in shape and size. Also, you may see a dark gray sopt similar to the aftereffect caused by a flashbulb. There may be other changes in vision: you may notice that the size of an object appears different for each eye or that colors don't look the same for each eye. These changes in eyesight are important symptoms and anyone who has these symptoms should make sure that he or she sees the eye doctor promptly. Do not assume you simply need a new pair of glasses and wait for an appointment in the future.

What Is the Doctor Looking For?

There are two main forms of macular degeneration: a dry form and a wet form. there is another form, which is uncommon, called pigment epithelial detachment (PED) that will be discussed later. In order to determine if you have macular degeneration and what form, the doctor will measure your vision and examine your eyes. By looking at the retina, the doctor will be able to tell if there is an abnormality. If drusen are found, you will want to schedule regular check-ups to make sure that no further damage is occurring. It may be necessary that photographs of each macula be taken to use for comparison with future examinations.

Dry or Atrophic Macular Degeneration

Drusen are considered to be a dry form of macular degeneration. When drusen are present for a long time, the macula may thin and stop working. This is referred to as atrophy or atrophic macular degeneration and it often causes a slow and progressive loss of vision. Although there is no medical or surgical treatment for this form of macular degeneration, eyesight may be helped somewhat with the use of special low vision lenses: magnifying lenses for close-up and telescopic to use some of their peripheral vision to help them see more clearly, and to cope more effectively with the practical tasks of every day life. Because the dry form of macular degeneration with dursen or atrophy can cange into the wet form, it is important for anyone with the dry form to monitor vision (with the Amsler grid, for example) and report any new changes to their eye doctor. Although the dry form of macular degeneration with atrophy can cause a large loss of detail vision, the damage done b atrophy is generally not as great as the damage that can be caused b the wet form. The dry form occurs in approximately 85 to 90% of people with macular degeneration. The wet form, which can be even more severe, occurs in only about 10% of people with macular degeneration.

Wet Macular Degeneration (Subretinal Neovascularization_ SRNV)

In the wet form of macular degeneration, abnormal blood vessels grow under the retina and lift the retina up, very much like the roots of a tree growing under a sidewalk. These abnormal blood vessels are called subretinal neovascularization, or SRNV. The abnormal blood vessels located under the retina may leak fluid, bleed, and lift up the retina. When this happens, vision is reduces. The longer the abnormal blood vessels continue to leak, bleed, and grow, the more detail vision will be lost. An eye with the wet form of macular degeneration will usually lose its ability to see detail. In some cases, laser treatment done promptly may stop or minimize loss of vision but laser treatment does not guarantee that vision won't be lost (see page 33, Laser Treatment). In addition, if the abnormal blood vessels occur in one eye, there is about a one in ten chance per year that they will occur in the other eye. The earlier that abnormal blood vessels are discovered, the more likely that some or much of the central (detail) vision can be saved. The later abnormal blood vessels are discovered, the less likely laser treatment can be done. In other words, pa close attention to your eyesight and see your eye doctor promptly if there is any type of change in your vision.

Pigment Epithelial Detachment (PED)

There is a third form of macular degeneration that is called pigment epithelial detachment (PED. In this form of macular degeneration a blister (a PED) can form in the macula, causing blurring or distortion of vision (see page 2). A PED occurs in less than 5% of people with macular degeneration. Laser treatment is not usually recommended unless abnormal blood vessels are also present. If you have a PED, you will want to have your eyes examined regularly to see what the condition does not worsen.

Fluorescein Angiography

If your doctor finds an abnormality an suspects the wet form of macular degeneration (abnormal blood vessels), a special test called fluorescein angiography will be done. To do the test, dye is injected into a vein in the arm. The dye travels through the body, including the eyes. With a special camera (not X-ray), a series of photographs of the retina is taken as the dye passes through it. the photographs show what changes have occurred n the retina and where those changes are located. Fluorescein angiography is necessary if the doctor thinks there is a chance that the patient could benefit from laser treatment. The photographs provide a kind of map that the doctor ses during laser treatment (see page 32). Fluorescein angioraphy is also usually done a few weeks following laser treatment to be sure that the laser has destroyed the abnormal blood vessels. There is another photographic test called indocyanine green angiography that is done the same way as fluorescein angiography. This test may give additional information that may be helpful if laser treatment is to be done.

Laser Treatment

In some cases, laser treatment can be done to prevent or lessen severe loss of eyesight if the abnormal blood vessels are discovered early enough. The laser beam is a hith energy light that turns to heat when it hits the parts of the retina to be treated. This heat destroys the abnormal blood vessels causing the wet macular degeneration and stops them from growing, leaking and bleeding. A scar forms as a result of the treatment. Vision does not usually improve after laser reatment and, in some cases, may even be somewhat worse. But loss of vision following laser, though immediate, is usually less severe than the eventual loss of vision that usually occurs if laser treatment is not done. In many cases, the visual distortion will disappear after laser treatment. Laser treatment only works about half the time. Since macular degeneration is a condition that is cause by the aging process, laser treatment is often only a means of temporarly preventing further loss of vision, or lessening the amount of visual loss that usually occurs if no laser is done. After laser treatment, vision may continue to worsen. But if laser is ndicated, the chances are that there will be less visual loss with laser than with no laser treatment. Without laser, loss of vision will usually continue. Before laser treatment, people with macular degeneration often notice that they have a dark or gray sopt in or near their central vision. The laser treatment will cause that spot to become completely and permanently black. That area of the macula is sacrificed to save the remaining portions of the macula.

The Decision to use laser depends upon the appearance and location of the abnormal blood vessels, as well as how much blood is prsent. In addition, the general health of the macula is important. In some cases, laser treatment may not always be helpful, or even possible, and is best not done. Even when laser treatment is considered successful, and the abnormal blood vessels have been destroyed, additional abnormal blood vessels can appear later and furthe damage vsion. The patient who is treated with laser should continually check the vision in the treated eye and tell the doctor immediately if there are new changes, such as a return of distortion or blurriness; in some cases additional laser treatment may be helpful. One reliable way for a person who has had laser treatment to measure changes is to learn to use the Amsler grid self test with the large "X". It may take some practice to learn to do the test without difficulty and accurately, but with this simple test, using a piece of paper and a pencil, the spot that was caused by the laser can be traced. By tracing it every day, it will be immediately evident when the spot has gotten bigger, or if a new spot has occurred somewhere else. If this happens, it usually indicates that the abnormal blood vessels have recurred. A person who has had successful laser treatment must use the Amsler grid everyday for the rest of his or her life. If there is a change, see your eye doctor promptly.

Frequently Asked Questions About Macular Degeneration