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Macular Degeneration
By Dr. Michael Klein
Age-related macular degeneration (AMD) is a very common condition in people older than 65. It’s the leading cause of legal blindness in the United States and the Western world. In fact, studies done in the U.S. and the U.K. report that more people have become legally blind from AMD than from all other causes combined.
The macula is located in the back of the eye. It’s about the size of a pencil point, but it’s loaded with important vision functions. AMD begins with the formation of little yellow fatty deposits in the macula. These deposits are called drusen, and are quite common in people older than 40; eventually, everyone develops drusen to some degree. But in people who are more likely to develop advanced AMD with vision impairment later on, these drusen become larger and multiply. We use criteria based on the size and amount of these deposits along with other retinal changes to determine who is at high risk to develop advanced AMD with potential vision loss.
We apply the term “macular degeneration” when drusen reach a certain size and amount, even though there is usually no vision loss. Most people don’t even know the large drusen are there unless they’re told. That’s just one reason why it’s important for your parent to have an exam. This is the most common form (about 90 percent) of macular degeneration, occurring in more than 20 percent of people over 65.
Advanced Dry AMD (Geographic Atrophy)
With this condition, more extensive damage slowly occurs to the retina, its pigmented cells, and the adjacent blood vessel layer. Cells drop out of the retina in the center of the retina (macula). In this form of advanced AMD, progressive loss of vision usually occurs slowly, where a patient might lose a line on the vision chart every year. However, eventually this advanced form of dry AMD can lead to legal blindness.
Wet AMD (Neovascular AMD)
In wet macular degeneration, blood vessels form and grow in behind the macula. These vessels, called “choroidal neovascularization,” can leak, bleed, and form scars, causing central vision loss that is both rapid and severe. A blood vessel can burst and hemorrhage, bringing on immediate symptoms. Usually, Wet AMD progresses quite rapidly, over days, weeks, or months.
Risk Factors
We don’t yet clearly understand the cause of AMD, but we have identified several risk factors:
- Age - As people get older, their risk for developing AMD goes up.
- Smoking – Smoking is consistently linked to AMD. The good news is that if you quit, the risk goes down significantly.
- Obesity –Those who are overweight are more likely to get AMD.
- Family History –Those with relatives with AMD are 3 or 4 times more likely to get the disease.
- Race – Northern Europeans with a light complexion have a higher risk.
- Genetics – In the past four years, a number of genes have been found that are associated with the likelihood of developing AMD.
Risk factors also depend on what a person’s retinas look like. If someone is 65 and has no large drusen, it is unlikely that individual will develop AMD over the next several years.
Prognosis for the Future
People with AMD may lose their ability to read and drive and distinguish fine details, but they won’t experience total vision loss. If your parent has AMD, they can retain their independence by seeing a low vision rehabilitation specialist and taking advantage of the many resources and devices available.
Unfortunately, we have not found a treatment that works for dry AMD, but we are working hard to develop effective treatments. I am happy to say that treatments for wet AMD have made huge advancements in recent years, and we are now able to help stop vision loss and even restore some vision loss in patients with wet AMD.
Dr. Klein specializes in macular and retinal vascular diseases at the Casey Eye Institute at Oregon Health & Science University. He received his medical degree from the Northwestern University Medical School, Chicago, in 1967. Dr. Klein completed his Ophthalmology residency at the University of Illinois Eye and Ear Infirmary in Chicago. He completed an Ophthalmology fellowship at Boston University, and a Retina fellowship at the Wilmer Institute at Johns Hopkins in Baltimore.
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