Saving Sight in Older Eyes

lose one eye, put your fist about three inches in front of your other eye and look straight ahead at this page,” directs Neil M. Bressler, This is what hundreds of thousands of people in the United States who suffer from age-related macular degeneration see, explains the Wilmer Eye Institute retinal specialist— everything around what they’re looking at, but nothing in the center. Those with advanced forms of the disease can no longer drive, read or even recognize the face of a friend because abnormal blood vessels have stealthily infiltrated and scarred the macula, the part of the retina that controls central vision.

Bressler calls age-related macular degeneration, or AMD, one of the nation’s most critical public health problems. The disease strikes men and women mostly over age 65. In its late stage it can come in either of two forms: a dry one or a wet one. Thinning and loss of retinal tissue characterize the dry form. In the wet version, abnormal blood vessels growing under the retina lift it up, much like the roots of a tree beneath a sidewalk, and fluid and blood leak from the vessels. The greater the growth of these vessels, called choroidal neovascularization, the more detailed the vision that will be lost.

Until recently, ophthalmologists have had few proven results to speak of in slowing down either form of AMD. Now a study—directed by Hopkins faculty and involving 22 medical centers around the world—is yielding some promising outcomes with the wet form, through an approach called photodynamic therapy.

To administer the treatment, Bressler first makes images of the abnormal blood vessels with a series of photographs, called fluorescein angiography, that give him a road map of the patient’s diseased retina. He then injects a photo-sensitizing drug, verteporfin, into the blood system, which travels to the retina and concentrates in the abnormal blood vessels. By next targeting the retina with a low-energy laser light, he induces a photochemical reaction between the light and the drug that damages the abnormal blood vessels and scar tissue.

The trick, Bressler says, is to minimize damage to the healthy tissue that still exists. “Because these vessels are growing right beneath the very sensitive retinal tissue, you’re trying to harm them just enough to keep them from growing and causing further vision damage. You have to be very selective in the way you’re destroying them.”

So far, photodynamic therapy is useful only when patients’ photographs show they have recently developed an aggressive, wet form of AMD. The technique cannot reverse critical damage that already has taken place. But Bressler feels certain the new therapy is an important step forward. Left untreated, the aggressive abnormal blood vessels would continue to grow and scar the retina. “For the person with AMD, the result would be increasingly impaired vision,” he says. “Photodynamic therapy has been able to stop that progression in more than half the patients we’ve studied.”

Finally, Hopkins also is testing a therapy called macular translocation in which eye surgeons move the retina slightly to allow lasers to burn diseased tissue without harming any healthy central retina tissue. Ophthalmologist Eugene de Juan has performed more than 350 of these procedures on patients with the wet form of the disease and in about one third has restored vision to allow them to read and drive again.

-- GL