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The retina From the smallest infants to the oldest patients, new approaches to retinal disease are repairing disorders of this delicate layer of sight-giving tissue. By Julie Miller Born more than three months prematurely in April 1997, twins Rosalie and Alexander Comfort weighed a pound and a half each, suffered from respiratory distress and faced the serious possibility of losing all or most of their sight. Along with their early delivery at only 24 weeks came exposure to a rare condition known as retinopathy of prematurity, in which normal formation of blood vessels in the retina is interrupted. “The worst case,” says their father, Tim Comfort, a chief petty officer in the Navy, “was that they would be able to see only shapes. The best was that with surgery, they would have very good, useable vision.” Until recently, little could be done to prevent retinopathy of prematurity, or ROP. Although 80 percent of cases typically resolve themselves without intervention, more than 500 infants a year are blinded by this disorder, in which the retina can be torn from its base by the pressure of rampaging capillaries. But with better screening in place, physicians are able to identify most infants at risk for the syndrome and prepare for a critical 72-hour window in which preventive treatment can be given. In the Comfort family’s case, that moment came in late July 1997, when their ophthalmologist in New London saw the first signs of impending retinal detachment and referred them to Yale. Two days later, associate professor Kathleen Stoessel, M.D., performed a procedure called cryopexy on the tiny infants, then only eight weeks old and still a month shy of their due date. One of several tools in the ophthalmologist’s arsenal, cryopexy freezes the rear portion of the retina, causing the threatening vessels to shrivel harmlessly away. The twins left Yale for Lawrence and Memorial Hospital in New London, and returned home to rural Uncasville, Conn., soon after with their sight intact. The retina, a critical link in the complex chain that turns light into sight, is the thin layer of tissue that generates nerve impulses from the stimulus of light and dark. When all is in good working order, words on a page or the view from our window reach the brain with perfect clarity. When retinal problems arise, the cause most often is the abnormal growth of the minute blood vessels within the retina. While not all cases are reversible, many once-discouraging cases respond to advanced techniques being applied at Yale, including cryopexy and laser surgery. Moreover, new diagnostic tools such as digital angiography are enabling ophthalmologists to diagnose retinal disorders earlier and more precisely than ever before—and to intervene before sight is lost. More than any other group of vision disorders, retinal disease affects patients along an extremely wide span of ages. Retinopathy of prematurity affects tens of thousands of infants born in the United States every year, although it spares most of them the loss of sight. Diabetic retinopathy, which is more widespread, is the leading cause of serious visual impairment among Americans between the ages of 20 and 64. And age-related macular degeneration is the chief cause of moderate to profound visual loss among adults over age 60 in the United States. In midlife,
an assault from diabetes
In some ways, this process is a mystery. “We don’t know the actual connection between diabetes and disease of the small blood vessels. What we have learned is that keeping tight control over blood sugar levels significantly reduces the chances of diabetes complications in the eye, and if you have complications already, it reduces the chances of their becoming worse,” Dr. Pieramici says. Theresa Kalman was not prepared for the damage diabetes did to her eyesight. The 53-year-old woman, who also has cardiovascular and kidney problems, awoke one morning unable to see. Her only warning had come the day before, when vision in one eye was cloudy. For the next several months, family members helped her negotiate a suddenly unfamiliar house and tend to the daily necessities of living. A series of visits to local doctors produced no clear explanation for the sudden loss of sight. Dr. Pieramici’s diagnosis was severe diabetic retinopathy in both eyes. He surgically removed a portion of the vitreous gel, along with the abnormal blood vessels and scar tissue. Once cleared of debris, the retina could be reattached. The surgeon also removed a cataract and placed an artificial lens in one eye. While the chances for partial success were good, he says, “We weren’t sure how much vision she would get back. We had to see how much damage there was to the retina.” Mrs. Kalman’s recovery was the happy kind. Several days after surgery, she could see well enough to read, watch television and care for herself again. For the first time in five months she saw her 16-month-old grandson’s face. “It was amazing,” she says. “I cried.” Laser and surgical treatments have reduced the incidence of legal blindness in patients with severe diabetic retinopathy from 50 percent to less than 5 percent, Dr. Pieramici notes, adding that Yale helped develop many of the advanced laser techniques during the past 20 years as a center for clinical trials. In addition, trials are being designed for surgical techniques to treat patients with chronic swelling of the retina that fails to respond to laser treatment. As remarkable as these interventions are compared to what was available to patients only a few years ago, the laser is still an invasive tool and can damage the retina. As molecular biology provides more tools for drug development, ophthalmologists are hopeful that new medications will provide less damaging ways of treating abnormal blood vessel growth. A puzzle
of the aging process
Age-related macular degeneration is the most common cause of vision loss among people over 65. In Mrs. Swift’s case, the presence of the abnormal blood vessel indicated the more destructive “wet” form of the disease in her left eye. “Dry” macular degeneration was diagnosed in the right. In the wet form, errant vessels from the wall of the eye make their way through the pigment layer and can slip under the retina. The vessels leak fluid or blood around the macula and damage sight. The hallmark of the more common dry macular degeneration is the atrophy of pigment cells, which appears as yellow spots in the retina. During the delicate laser surgery that followed, Dr. Stoessel cauterized the abnormal vessel in Mrs. Swift’s left eye in an attempt to prevent further damage. But over the past several years, additional laser treatments have been required to treat abnormal vessels that developed from the underlying macular degeneration. Although her left-eye vision is blurred, management of her right eye has been more successful. Despite its progression from dry to wet form of the disease, the right eye has responded well to laser treatment. Two years ago, a buildup of blood and fluid in the macula of her right eye was treated promptly with laser, and her blurred vision has improved and been stable for more than a year. Mrs. Swift, who lives alone, has a life filled with friends, church activities and three grandchildren. With the help of glasses, her eyes still work. She lives independently, drives a car, cooks, reads and enjoys watching birds at the feeder in her back yard. Her sight is generally good, she feels, despite the loss of central vision on the left side. “When I put my glasses on,” she says, “I’m not really aware of it.” More than 90 percent of patients with macular degeneration have the dry form, for which there is no effective treatment, according to the National Eye Institute. Laser treatment, the only proven therapy for the wet form, is most effective if the condition is diagnosed early. The incidence of macular degeneration increases dramatically with age. Whereas fewer than 10 percent of people have significant macular changes at age 65, nearly 50 percent have some degree of change at age 80, says clinical faculty member David Parke, M.D. “The importance of these figures takes on even greater meaning as we tend to live longer.” Many people in their 70s and 80s develop significant macular disease, while others show little evidence of it. “If we knew which variables were involved in preventing macular degeneration in some patients, there is the potential that they could be used as a treatment to prevent the growth of abnormal vessels,” says Dr. Stoessel. “We have to examine the growth factors that allow blood vessels to develop normally and the factors that prevent too much blood vessel growth. We need to understand these better in order to learn what goes wrong when children are born prematurely with stunting of the retinal blood vessels. The growth factors in retinopathy of prematurity may turn out to be similar to the growth factors in macular degeneration.” Looking to
the future
More than a year has passed since Rosalie and Alexander Comfort’s eyes were treated with cryopexy. The retinal vessels have regressed, and the children, now 17 months old in late September, are doing well. Alex had surgery at the end of August on his eye muscles. He is doing well but is frustrated at having to wear eyeglasses for nearsightedness, which is common among children with retinopathy. “Now the biggest challenge is keeping his glasses on. He has the habit of flinging them off,” says his mother, Diana Comfort. They keep two pairs around the house because they never know where his glasses will end up. Rosalie doesn’t wear glasses and didn’t need the surgery. Like her brother, her development seems to have been delayed slightly by weaker eyesight, but both children seem to be catching up. The Comforts, who also have a 4-year-old daughter, are happy with the twins’ progress. And while they had hoped Alex wouldn’t need glasses, they feel good about his future. “He’ll be able to see. Without some kind of vision, he would be very limited,” says his father, who looks forward to introducing his son one day to the outdoor pursuits he enjoys. “I like to hunt and fish, and I want to take him along.”YM |
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