Macular Degeneration

By Christine Haran

When most people are asked which of their five senses they would most hate to lose, they often say vision. Sadly, for millions of older adults, this worst-case scenario has come true. Macular degeneration, which is caused by the destruction of light-sensitive cells in the eye, causes a loss of central vision, which is absolutely essential for reading and driving. Although glaucoma and diabetes are better known as causes of vision loss, macular degeneration is responsible for more irreversible loss that those two conditions combined.

Macular degeneration researcher Barbara Brody, a clinical professor of ophthalmology and family and preventive medicine at the University of California, San Diego, and the director of the community ophthalmology division at Shiley Eye Center, is the lead author of a recent study about quality of life in people with macular degeneration. Below, Brody explains how and why the condition affects vision and how older adults may learn to adjust to the loss of much of their sight.

What is age-related macular degeneration?
Age-related macular degeneration (AMD) is a disease of the central retina, which is called the macula. The retina is the tissue at the back of the eye that transmits images to the brain. The degeneration of cells in the macula affects the ability to see straight ahead. It's the straight-ahead, or central, vision that allows us to have really clear sight. It allows us to see sharp detail, to read, to drive, to see people's faces. AMD does not typically affect the peripheral vision, or side vision.

What are the different types of the condition?
There are two types of AMD: dry and wet. About 90 percent of the people with macular degeneration have the dry form of the disease. In this form, there is a slow breakdown of the light-sensitive cells in the macula. This condition may take years to develop, and people usually lose vision very slowly. It often happens in one eye and then may go to the other eye.

The wet form, though less common, is the version of the disease that can cause major loss of vision. It occurs when new blood vessels behind the retina start to grow towards the macula. These new blood vessels are very weak and they can start to leak or bleed. This damages the macula and causes rapid vision loss.

What are the risk factors for the condition?
The biggest risk factor is advanced age, so the older we get the more at risk we are. It affects about 20 percent of people aged 65 and older, and about 30 percent of people aged 74 and older.

There are other risk factors that are less well understood. Smoking has been shown to be a risk factor. Some people seem to think that women may be more at risk, though that's a little bit hard to factor out because women tend to live longer than men. A family history of macular degeneration also increases risk.

How common is the disease?
It's estimated that there are as many as 15 million people in the United States who have some form of macular degeneration. It is the leading cause of irreversible vision loss in older adults worldwide, and it's estimated that it affects as many as 30 million people in the world.

How does AMD affect vision?
By and large, with the dry form of macular degeneration, people see a blurred image initially. As more and more of the millions of cells in the macula get destroyed, there may be a blank spot in the center of the vision.

With the wet form, there is a much more pronounced loss of central vision. And some people with advanced macular degeneration may have occasional visual hallucinations. The phenomenon is well known, but people don't tend to discuss it. So you really have to ask them to find out about it unless they're in a very trusting relationship.

Those are the general things, but it seems to affect each person's vision in slightly different ways since different people may have slightly different patterns to their loss of cells.

Most people, even those with advanced macular degeneration, will not lose all of their sight because they will retain their peripheral vision. They will be able to get around a room quite well. And out of the corner of their eye, they can see that a pin dropped on the floor. But when they then turn to pick it up, they can't see it any more because it's moved into their central vision.

What are the early signs of AMD?
One of the first signs of the wet macular degeneration is that a straight line becomes a wavy or distorted line. That's why the Amsler grid, a pattern of lines, is used to identify wet macular degeneration early on.

In the dry form, people start to see a blurred spot in their central vision. Things aren't as sharp and then a letter may start to be missing or something else is missing in what they're looking at. The dry form can turn into the wet form of macular degeneration. And it's possible to have different degrees of macular degeneration in each eye.

Can AMD be prevented?
The Age-Related Eye Disease Study, funded by the National Eye Institute, found that a particular formulation of vitamin C, vitamin E and beta-carotene, which are antioxidants, combined with zinc and copper, slowed the progression of the disease in people who had the intermediate form of macular degeneration. Since most people who have macular degeneration might have some other medical condition, it's best to have their primary care doctor involved in determining whether they are good candidates for this formulation. If these vitamins are potent enough to be in a therapeutic dose, they may have some other consequences for the individual.

Are there screening tests for macular degeneration?
There is no screening test for macular degeneration such as a mammogram. In general, it is recommended that adults have a full, dilated eye exam by an eye professional every one to two years. As part of that examination, the doctor is often able to identify early signs of macular degeneration, or "drusen," which are yellow deposits on the macula. In the early stage, an individual has several small drusen or a few medium-sized drusen in one or both eyes. And then the intermediate stage is when they have many medium-sized or one or two large drusen. The disease is advanced when they actually see that dry macular degeneration, the breakdown of the cells, or these new abnormal blood vessels that are the hallmark of the wet form.

For people with early signs of the disease, more frequent exams may be suggested and the individual may be instructed to use the Amsler grid at home, and call if changes are noted at any time between exams. A regular eye examination is also important to screen for glaucoma since both macular degeneration and glaucoma, which affects the peripheral vision, can occur together.

What kind of treatment for AMD is available?
There is no treatment available for the dry form of the disease. But there are indeed a variety of different treatments for people with certain types of wet macular degeneration. These are laser surgery and photodynamic surgery, which uses a different kind of laser. These surgeries have been shown in studies not to cure the disease but to slow the progression of the vision loss.

Both treatments can take place in an ophthalmologist's office. What they're trying to do is stop the blood vessels of the wet form from leaking.

Drugs that might prevent the formation of new blood vessels in a specific type of macular degeneration are under study right now. Some of these studies are being done here at UCSD Shiley Eye Center. There is a lot of hope, but they haven't been proven yet.

How can AMD affect mental health?
We all value our independence, particularly in American culture. So the loss of independence, such as loss of the ability to drive, is very much a contributor to depression. It's a very devastating condition. We've asked people "What is your worst medical problem?" And these are people who have had heart disease, all kinds of cancers, and on and on. Over 90 percent say that macular degeneration is their worst medical condition.

In our studies on quality of life, we found that approximately one-third of participants met criteria for depression. That's about twice the level of depression one would find in this age group. And it's also very important because the depression that people experience with macular degeneration is very closely associated with the disability of the disease.

When you take two people, for example, who have experienced the same level of vision loss, the person who is depressed is much more disabled than the person who is not, even though they would appear to have suffered the disease in a similar manner.

That's something that is very important at this point in time because much more is known about successful treatment of depression than is known about curing macular degeneration.

So how can people cope with this vision loss?
I think it's important to find ways to engage in meaningful activities. For example, one 78-year-old participant in our self-management research program at the eye center decided to try something she had enjoyed in a different way. She had been a pilot and decided to try sky sailing, with an instructor. Since people with AMD typically retain their peripheral vision, she could see the horizon and stay level with it.

Another important step is to learn more about the disease so that you understand it and are be able to explain it to your friends and loved ones. And there are three things that people can do to maximize the vision that they have: magnify, improve lighting and improve contrast. Improving the lighting is important because people have lost some of their light sensitive cells. Improving the contrast in their daily life can help people identify things. For example, one woman said, "Well, I've given up eating the cucumbers I love because I can't see them on the plate." But if she had put her white cucumbers on a blue plate instead of a white plate, she'd be able to find them.

There are a number of places that sell materials for people who have various types of disabilities. For example, people can mark the oven with fabric paint or raised dots. And the phone company may provide large digit telephones. These are the kinds of things that are available in most every area. But there is so much more we need to do, as a society, to allow people with macular degeneration to participate fully in the lives of their community.

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