Getting older raises risk of vision loss
With age as the highest risk factor for macular degeneration, people 50 and older should be on the lookout for signs of vision loss. It could be a sign of age-related macular degeneration or AMD.
“I see a lot of macular degeneration,” said comprehensive ophthalmologist Eugene C. Ciccarelli, MD, of Hyannis. Given that there is a large percentage of older residents on Cape Cod, it’s no surprise.
Macular degeneration refers to the disruption and breakdown of the macula, a spot in the back of the eye that allows you to see details and objects directly in front of you. It’s part of the retina, the interior lining of the eye, which contains cells that convert light into impulses transmitted by the optic nerve to the brain, where they’re translated into images.
With AMD, you retain peripheral or side vision, as the remainder of the retina away from the macula is undamaged. You may lose the ability to read and drive but still see well enough to get around in your home, Dr. Ciccarelli said.
According to a 2016 article in the medical journal Eye and Vision, AMD affects 11 million Americans – more than double the amount with Alzheimer’s disease and more than the combined cases of glaucoma and cataracts – and is expected to increase to 22 million Americans by 2050. It’s the leading cause of vision loss in industrialized nations.
There is no cure yet for "dry" AMD, which worsens with time, but there is treatment for the more severe form known as “wet” AMD. Most people with AMD have the dry form.
Dry and Wet AMD
The hallmark of dry AMD is the accumulation of drusen, which Dr. Ciccarelli likened to “retinal fecal matter” – deposits of fat and protein that build up. With dry AMD, the macula becomes thinner and loss of central vision occurs slowly. It’s postulated that drusen deposits may interfere with interaction between the eye’s choroid and retinal pigment epithelium.
The choroid is a layer behind the retina that’s filled with blood vessels and supplies nutrients to the retina. The retinal pigment epithelium, or RPE, is a thin layer of pigmented cells beneath the retina’s photoreceptors.
“The dry type can get changes in the RPE,” Dr. Ciccarelli said. “That RPE can drop out. It looks like a map. Those areas don’t see.”
In wet AMD, abnormal blood vessels grow from the choroid. They can leak blood and fluid and cause the areas of the retina to bulge. This initially distorts vision but can quickly change to destroying it.
“The wet type can cause blindness within days,” Dr. Ciccarelli said. “Macular degeneration is relentlessly progressive.”
About 10-15 percent of people with AMD have the wet form, according to the American Academy of Ophthalmology.
Another form of macular degeneration called Stargardt disease is not age-related, rare, affects young people between ages 6 and 20, and is caused by inheriting two copies of a recessive gene.
Age is the number one risk factor for AMD, but others include:
- Being overweight or obese
- Having high blood pressure
- Having heart disease or high cholesterol blood levels
- Eating lots of saturated fats
“Smoking is a definite risk factor for progression of AMD,” Dr. Ciccarelli said, and suggested a diet high in green, leafy vegetables to help lower risk.
No one chromosomal mutation or gene has been shown to be a cause of AMD.
“It probably involves a combination of a number of genetic traits,” he said.
Detection and Treatment
Your ophthalmologist can look for signs of AMD during an examination by using eyedrops that widen your pupils. More extensive imaging of your retina can be done with optical coherence tomography (OCT), in which a machine generates very detailed pictures, or fluorescein angiography, which photographs your retina as dye, injected into a vein, travels through the eye’s blood vessels. A third technique, optical coherence tomography angiography (OCTA), also looks at the eye’s blood vessels, but doesn’t require dye.
Eye exams can spot deposits of drusen before you start losing vision, in the early stage of AMD. Regular exams are especially important for people with one of more risk factors, according to American Macular Degeneration Foundation.
Changes caused by AMD can be quite gradual and may not be noticed at first. One way to detect vision changes is to look at an Amsler grid twice a week. This square of perpendicular lines resembles graph paper with a dot at the center. By looking at the grid from about 12-15 inches away with one eye at a time, you can check for lines that appear wavy, faint or blurry. Dr. Ciccarelli said anyone noticing distortions should contact their ophthalmologist immediately.
You can download and print an Amsler grid and instructions for use from the American Macular Degeneration Foundation: https://www.macular.org/amsler-chart
Injections of drugs that inhibit growth of blood vessels are the standard treatment for wet AMD. The medicines are known as anti-VEGF (anti-vascular endothelial growth factor) drugs. These shots are given into the eye once every four to six weeks using a very fine hypodermic needle, and they also help curtail leaking of fluids from abnormal blood vessels under the retina. Some patients find the injections not only slow progression but have improved their eyesight, Dr. Ciccarelli said.
“Now, after a year or two, about half are seeing 20/40,” he said. “Most are improved by treatment.”