New treatments for AMD

Low vision means it’s difficult, perhaps impossible, to perform everyday activities such as reading or driving even with corrective eyeglasses, contact lenses or surgery. But it isn’t normal, not even in older people. Dr. Patricia Harvey, a retinal specialist at Toronto Western Hospital, recommends an eye exam at age 50 to screen for diseases of aging eyes. After that, regular testing will depend on what the eye-care professional has found. The earlier treatment can be started, the greater the chance of delaying or moderating damage to eyesight.

Vision in people over 50 is most commonly compromised by glaucoma (increased pressure within the eyeball), cataracts (clouding of the lens), damage to the retina caused by diabetes or age-related macular degeneration (AMD).

A hidden sight destroyer
AMD attacks the macula, part of the light-sensitive retina covering the interior of the back of the eye. A healthy macula is vital for precise central vision. The disease affects both eyes, often at different rates. In the initial or “dry” stage, there may be no indication of a problem. By looking through a dilated pupil, an eye-ca professional can spot yellow deposits called drusen under the macula that are typical of dry AMD.

Dry AMD can progress to “wet” AMD when the deepest layer of the retina thins and cracks and underlying blood vessels grow through, causing bleeding, leaving opaque deposits and raising the other layers of the retina like a blister. When light strikes the cells there, the message won’t reach the optic nerve. The development of wet AMD can occur suddenly, so any deterioration in sight needs immediate medical attention.

In the past, Harvey says, the disease wasn’t even discussed with patients unless they had noticeable visual loss because there was no treatment. “There wasn’t much to do for AMD patients except rehabilitate them once they’d lost their vision,” she says. Now, patients are told they have AMD, advised to take a certain vitamin mixture and to test their vision regularly with an Amsler grid (graph paper with a dot in the centre, which the patient looks at, covering first one eye and then the other and noting if there are distortions). Changes should prompt a call to an ophthalmologist.

Making progress in treatment
The current treatment for wet AMD is photodynamic therapy with Visudyne (verteporfin). This dye is given intravenously and absorbed by the abnormal blood vessels in the eye. They are illuminated by a special light, which excites the dye, killing or coagulating the blood vessels. As the fluid absorbs, the retina flattens out and the vision stabilizes or improves. “This is a real breakthrough,” Harvey says, “because we can leave the other layers of the retina intact and kill the blood vessels underneath.”

Other trials are currently underway that may lead to new treatments for this growth of blood vessels, she notes.

Slowing the disease
A clinical trial, referred to as the Age-Related Eye Disease Study (AREDS), conducted by the National Eye Institute in the U.S. concluded people at high risk of developing AMD could benefit from taking a specific combination of antioxidants (vitamins C and E and beta carotene) plus zinc. Those studied had intermediate AMD and there is no evidence yet that the AREDS formulation can slow the progress of early AMD. The study stressed older people, especially those being treated for chronic conditions, should consult a physician before taking high-dose vitamins and minerals.

“The study showed patients who have a healthy diet rich in the green and orange vegetables will do better than those who don’t,” Harvey says. Beta carotene supplements can raise the risk of lung cancer in people who smoke. Unfortunately, smokers have a six- to 10-fold increased risk of developing AMD, and since a family history of the disease is another risk factor, she suggests children of people with AMD stop smoking.

People with light skin and those with blue or light-coloured eyes are at risk of AMD. Harvey suggests protecting the eyes from ultraviolet rays is prudent and non-invasive. “You can put UV filters in your regular glasses or wear sunglasses that are UV blockers,” she says.