March 29, 2004.
By JENNI LAIDMAN,
Doctors at a Toledo clinic are offering an experimental treatment for the most common form of blindness in the United States -- macular degeneration.
Each year some 200,000 Americans learn they're losing their sight to the worst form of the disease. Abnormal blood vessels growing beneath the retina's center, known as the macula, can distort and destroy vision. These new blood vessels often leak.
One of the best approved treatments is photodynamic therapy, which uses a laser and a photosensitive drug to kill the malformed vessels. Doctors infuse the drug intravenously, then point a laser at the damaged vessels. The drug reacts with the cool laser, blocking the vessel. But clinical trials show photodynamic therapy at best stabilizes the deterioration in some patients. It does not restore sight.
Now, early trials on a new generation of drugs seem to offer a bit more hope.
"This is one of the first treatments that has actually shown improvement," said Ira K. Orgel, an ophthalmologist at Retina Vitreous Associates, Inc. Dr. Orgel is the local princiipal investigator for one new treatment.
Lucentis, manufactured by the San Francisco biotech firm, Genetech Inc. -- along with another promising experimental compound called Macugen -- works by shutting down blood vessel growth.
Both drugs act on compounds called growth factors, which urge the body to grow new blood vessels. Cancer researchers hoping to starve tumors of blood supply pioneered antigrowth-factor drugs. In fact, Lucentis is a modified version of a Genentech cancer drug recently granted U.S. Food & Drug Administration approval.
In a small, early trials of Lucentis, 26 percent of 53 patients who received the drug were able to see three more lines on a vision chart after treatment. Patients on average gained two lines of vision in this small trial.
"With photodynamic therapy, you see stabilization in a third of the patients," Dr. Orgel said. "Perhaps in only 1 percent do you see any improvement."
On average, Lucentis patients gained an average of at least two lines a chart. The average photodynamic therapy patient loses a line.
Patients in Toledo who sign up for the Lucentis trial won't know if they're receiving the new drug or photodynamic therapy.
The other drug aimed at blood-vessel growth, Macugen, performed as well as Lucentis in a small Phase II trial. Macugen is a product of a Manhattan firm, Eyetech. Twenty-five percent of those treated with Macugen saw an additional three or more lines on a vision chart after treatment. But when Macugen treatment included photodynamic therapy -- the standard care for wet macular degeneration -- results were even better. Sixty percent of patients saw three more lines on the vision chart.
But the best measure of success comes not in these small trials, but in the large nationwide Phase III trials, such as the one Dr. Orgel's Lucentis patients will participate in.
Macugen recently completed Phase III trials - the last step before the FDA can consider approving medication for market. The larger study continued to show the drug effective, but not quite as promising as initial results appeared.
Vision improved or stabilized for a third of the patients in the Phase III trial. Among these, 6 percent gained three or more lines, 11 percent gained two lines, and 22 percent gained one line, said Dr. Lawrence Singerman, president of Retinal Associates in Cleveland.
Still, Dr. Singerman said, the results were "very dramatic." He was the leading recruiter in the Macugen trial, which included 1,200 patients nationwide, and active in many other studies.
Although the much larger Phase III trial failed to show the high percentage of dramatic improvements found in the earlier Macugen study, the drug still performed better than photodynamic therapy, he said.
Besides producing better results than regular therapy, Dr. Singerman says Macugen can help many more people than photodynamic treatment.
"Photodynamic therapy cannot even be tried in very large lesions. This offers a treatment for many more types of lesions."
Patients who participate in the Lucentis trial in Toledo will be randomly assigned to receive either photodynamic therapy and sham Lucentis injections, or sham photodynamic therapy and real Lucentis injections.
All in all, Dr. Singerman says, the hope for better treatment of macular degeneration is growing.
Another important step in dealing with macular degeneration would be preventing its onset. While it's unclear why one individual develops the eye disease and a second doesn't, smoking and diet play some role. People who eat lots of fruits and vegetables, especially green leafy vegetables, have a lower incidence of macular degeneration. Physicians also often advise patients to take a multiple vitamin supplement with zinc, which limits oxidative damage that can lead to macular degeneration.
Another risk factor is exposure to light. Although we've grown accustomed to thinking of invisible UV light as a troublemaker, it turns out a portion of the visible light spectrum plays a role in macular degeneration.
Visible light is made of a rainbow of colors. Beam that light through a prism and the colors reveal themselves, from the low-energy red wavelengths, to the very energetic blue.
A study of 838 men who made their living fishing showed that those who were exposed to the highest levels of blue light in the preceding 20 years were most likely to develop macular degeneration. Light exposure earlier in life appeared to have no effect.
In animals, short periods of exposure to UV light and blue light caused retinal damage. In fact, the retina is much more sensitive to blue light than any other wavelength of visible light, laboratory tests show.
But for much of our life, our own lenses protect us from the blue light spectrum. Age gradually erodes that protection, contributing apparently to macular degeneration.
For people who undergo cataract surgery, the risks may be greater yet, said Paul Ernest, a ophthalmologist in Jackson, Mich. Artificial lenses implanted during surgery lack a natural blue-light barrier, and some believe this leads to higher levels of macular degeneration among cataract patients.
"That's the debate," Dr. Ernest said. The question awaits an adequate study to address it. Small studies are thus far inconclusive.
Lenses that block blue light for cataract patients have been on the market for a year. They are about $15 more than the other cataract lenses, Dr. Ernest said, a price that cannot be passed on to the patient. The lens manufacturer pays for some of Dr. Ernest's research. "I've put in thousands already," Dr. Ernest said. "I look at it this way, there's no down-side."
So what about the rest of us? Should we be wearing blue-blocking sunglasses to shield our aging eyes? There is no definitive research to say so. But some people are inclined to play it safe. "I have them," Dr. Ernest said. "And I filter out all the blue light when I operate."
Contact Jenni Laidman at: firstname.lastname@example.org or 419-724-6507.
© 2004 The Blade.
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