In just over one month, Lynn Dahling lost nearly 80 percent of her vision in her left eye.
That was in December 1999. By Christmas Eve, she was frightened and unclear how it had happened so quickly. Her doctor diagnosed the problem as uveitis, an inflammation inside the eye that can cause sudden loss of sight.
Eighteen months later, after several setbacks, Dahling is seeing in both eyes again. She is one of the first success stories for a still-experimental approach to treating eye diseases by surgically implanting long-lasting medicine at the back of the eye. If approved by regulators, the new technology, developed by a Watertown company, could become widespread and replace older medicines that have serious side effects.
Dahling's doctor initially gave her eye drops, but they did not work. Then he prescribed prednisone, a generic drug that healed the inflammation and restored her eyesight. But that caused the side effects of weight gain, increased blood pressure and depression.
Constantly squinting and barely passing a vision exam to renew her driver's license, Dahling, a patient coordinator at Massachusetts General Hospital, wanted to stop taking the drug.
``I hated the moodiness and putting on weight, and begged for something different,'' said Dahling, who is in her mid-30s.
Her doctor told her the alternative was monthly drug injections directly into the eye that could potentially damage the retina. But another surgeon suggested a radically different treatment.
He convinced her to try an unproven time-released drug delivery system that is surgically implanted into the back of the eye (about a quarter of an inch from the colored part of the eye, called the iris). The device emits microscopic amounts of a mild steroid over 1,000 days.
Two months ago, she got the pencil point-sized implant, called Envision, in a 20-minute outpatient procedure. Since then, her vision has been nearly back to normal, with none of the drug's side effects.
"I feel like I've got my life back,'' she said Tuesday.
Envision was developed by Watertown's Control Delivery Systems Inc., which five years ago created a first-generation eye implant device that releases an antiviral drug over an eight-month period for the treatment of cystomegalovirus (CMV) ritinitis, a debilitating condition that afflicts AIDS patients. The device is now used less frequently because of significant improvements in AIDS medications.
Control Delivery is using Envision in a series of clinical trials for uveitis; for age-related macular degeneration, the leading cause of blindness in people over 50; and for diabetic macular edema, a major cause of vision loss in people with diabetes.
Treatments for these diseases are in clinical trials with Control Delivery's partner, Bausch & Lomb Inc., the developer and marketer of health-care products for the eye. Control Delivery officials are hoping to get their first Food and Drug Administration approval of Envision for diabetics in late 2003.
``Their (Envision) concept is promising,'' said Dr. Matthew Davis, emeritus professor of ophthalmology and visual science at the University of Wisconsin. ``But whether this device and the drug for these particular diseases will work is still unclear because it's relatively early, as few patients have had the implants.''
However, given the company's early success with AIDS patients, Davis, a Control Delivery consultant, said implant technology has been generally accepted by ophthalmologists.
Control Delivery is also evaluating a comparable sustained release drug to treat cancerous brain tumors with an implanted, refillable device. A Phase II study is slated to start this summer using bleomycin, an anti-cancer drug.
Beyond vision and brain diseases, Control Delivery recently began animal testing of a screw-type device implanted in sheep. It is designed for people with severe osteoarthritis, possibly delaying the need for joint-replacement surgery.
``By delivering medicine locally - to the eye, the brain, a joint - you provide a constant rate of a potent drug in the surrounding tissue,'' said Paul Ashton, Control Delivery president and chief executive.
By contrast, when drugs are injected into the blood stream to treat eye diseases, they often fail to reach their destination in sufficient quantities. And drops work well on the surface of the eye, but don't get to the back of the eye.
Inserting a sustained-release drug exactly where it is required also eliminates the side effects of injected or swallowed drugs that travel throughout the body.
Still, the company acknowledges some patients in its clinical trials have experienced glaucoma, in which increased pressure within the eye impairs vision and may slowly cause eye damage. Another side effect is infection from the surgical incision. Those problems, said Smith, can be corrected with existing medications.
Several other companies are also developing new ways of treating eye diseases. QLT PhotoTherapeutics Inc. of Vancouver, Canada, and its partner, Atlanta-based Ciba Vision Crop., use Visidyne, a combination of a dye and a laser system to preserve the vision of patients with age-related macular degeneration. About 12 million Americans have this disease.
Visidyne works by injecting into a patient's arm a dye that reacts to light. As the dye passes through the body and moves up to the eye, it pools in the abnormal blood vessels that have grown and leaked in the central part of the retina. Ophthalmologists then shine into the eye a low-power laser light that functions like a spot welder to seal off the leaking blood vessels to prevent further vision loss.
A third company, Eli Lilly & Co., is working on a prevention drug for diabetics who do not have clinically significant vision problems. Called a kinase C inhibitor, it is being tested in diabetics with some visual problems, with the goal of slowing the progression of diabetic macular edema.
For Bausch & Lomb, Control Delivery's Envision product line has been described as one of the most important research initiatives in the company's history.
The company bankrolled Control Delivery for several years before venture capitalists ponied up $34 million last summer. Those funds enabled the small company to expand its nonvision clinical trials.
