Diagnosis and Management of Macular Degeneration
How are the eyes affected in age-related macular degeneration?
Age-related macular degeneration (AMD) is a deterioration or breakdown of the eye’s macula. The macula is a small area in the retina — the light-sensitive tissue lining the back of the eye. The macula is the part of the retina that is responsible for your central vision, allowing you to see fine details clearly.
Even though the macula makes up only a small part of the retina, it is much more sensitive to detail than the rest of the retina, called the peripheral retina. The macula is what allows you to thread a needle, read small print, and read street signs. The peripheral retina gives you side (or peripheral) vision.
If someone is standing off to one side of your vision, your peripheral retina helps you know that person is there by allowing you to see their general shape. It is your macula that allows you to recognize the details of the person’s face.
Many older people develop macular degeneration as part of the body’s natural aging process. There are different kinds of macular problems, but the most common is age-related macular degeneration.
The retina is made up of many layers that work together to help you see clearly. AMD develops when a layer under the retina called the retinal pigment epithelium (RPE) is affected by deposits of tiny yellow or white pieces of fatty protein called drusen, or by other age-related changes.
With AMD, you may have blurriness, dark areas or distortion in your central vision, and perhaps permanent loss of your central vision. It usually does not affect your side, or peripheral vision. For example, with advanced AMD, you could see the outline of a clock, yet may not be able to see the hands of the clock to tell what time it is.
AMD alone almost never causes total blindness. People with more advanced cases of AMD continue to have useful vision using their side, or peripheral vision. In many cases, macular degeneration’s impact on your vision can be minimal.
When AMD does lead to loss of vision, it usually begins in just one eye, though it may affect the other eye later.
Many people are not aware that they have macular degeneration until they have a noticeable vision problem or until it is detected during an eye examination.
In its earliest stages, macular degeneration may cause the following symptoms:
- Blurry distance and/or reading vision;
- Distorted vision — straight lines will appear bent, crooked or irregular;
- Dark gray spots or blank spots in your vision;
- Size of objects may appear different for each eye;
- Colors do not look the same for each eye.
Doctors and researchers don't know the exact causes of AMD but it is clear that this disease is strongly associated with age, since AMD occurs as people grow older. One large study found that the risk of getting AMD jumps from about 2 percent of middle-aged people in their 50s to nearly 30 percent in people over age 75.
Our bodies constantly react with the oxygen in our environment. Over our lifetimes, as a result of this activity, our bodies produce tiny molecules called free radicals. These free radicals affect our cells, sometimes damaging them. This is called oxidative stress and is thought to play a major role in how AMD develops.
Heredity is another risk factor for AMD. People who have a close family member with the disease have a greater chance of developing AMD themselves.
Some studies have shown that inflammation (swelling of the body’s tissues) may play a role in AMD development. Inflammation is the way the body’s immune system fights off infection or other things it considers “invaders.”But an overactive immune system with its associated inflammation may be a risk factor for AMD.
Smoking and high blood pressure are associated with the wet form of AMD. Research also suggests there may be a link between being obese and having early or intermediate-stage AMD develop into advanced (wet) AMD.
Dry Age-Related Macular Degeneration (AMD)
Most people who have AMD have the dry form. This condition is caused by aging and thinning of the tissues of the macula. Macular degeneration usually begins when tiny yellow or white pieces of fatty protein form under the retina. These deposits are called drusen. Eventually, the macula may become thinner and stop working properly. With dry AMD, vision loss is usually gradual.
People who develop dry AMD must carefully and constantly monitor their central vision. If you notice any changes in your vision, you should tell Doctor Murphy right away, as the dry form can change into the more damaging form of AMD called wet (exudative) AMD.
Wet Age-Related Macular Degeneration (AMD)
The wet form of macular degeneration occurs in about 10 percent of all macular degeneration cases, but it can cause more damage to your central or detail vision than the dry form.
Capillaries, or tiny blood vessels, extend into all tissues of the body, bringing in nutrients and carrying off waste products. Capillaries usually don’t increase in size or number, but if they do, it is called abnormal blood vessel growth.
Wet AMD occurs when abnormal blood vessels begin to grow underneath the retina. This blood vessel growth is called choroidal neovascularization (CNV) because these vessels grow from the layer under the retina called the choroid. These new blood vessels may leak fluid or blood, blurring or distorting central vision. Vision loss from this form of AMD may be faster and more noticeable than that from dry AMD.
The longer these abnormal vessels leak or grow, the more risk you have of losing more of your detailed vision. Also, if abnormal blood vessel growth happens in one eye, there is a risk that it will occur in the other eye. The earlier that wet AMD is diagnosed, the better chance you have of preserving some or much of your central vision. That is why it is so important that you and Doctor Murphy monitor your vision in each eye carefully.
Use of Amsler Grid to Monitor Age-Related Macular Degeneration (AMD)
If you have been diagnosed with dry AMD, you should use a chart called an Amsler grid every day to monitor your vision, as dry AMD can change into the more damaging wet form.
To use the Amsler grid, wear your reading glasses and hold the grid 12 to 15 inches away from your face in good light.
- Cover one eye.
- Look directly at the center dot with the uncovered eye and keep your eye focused on it.
- While looking directly at the center dot, note whether all lines of the grid are straight or if any areas are distorted, blurry or dark.
- Repeat this procedure with the other eye.
- If any area of the grid looks wavy, blurred or dark, contact your ophthalmologist immediately.
If you detect any changes when looking at the grid, you should notify Doctor Murphy immediately.