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May 29, 2005
Evidence for the Oxygen/Cataract Connection
Am J of Ophthalmol 2005;139:302-310
A study by a group at Washington University School of Medicine in St. Louis is shedding new light on the role oxygen plays in cataract development.As reported in the American Journal of Ophthalmology, they measured oxygen concentrations in the eyes of patients undergoing retinal surgery. “It’s fairly well-accepted in the field that anyone over the age of 50 who has vitrectomy surgery will develop a cataract within two years,” Just before surgery, Dr. Holekamp measured oxygen levels adjacent to the lens and near the center of the eye in the vitreous gel of 69 eyes. Before retinal surgery, oxygen concentrations were very low in both places. After surgery, oxygen levels in both locations were about eight times higher than normal.“It seems one of the important functions of the vitreous gel is to keep oxygen away from the lens,” When we remove the gel, we remove that protective mechanism A co-investigator, David C. Beebe, PhD, believes the same kind of mechanism may contribute to cataracts that form as people age. The difference is that in age-related cataracts, the gel breaks down over several years. In vitrectomy patients, the gel disappears all at once.They believe that when the gel separates from the retina or begins to break down and liquefy, it allows fluid to flow over the surface of the oxygen-rich retina and carry that oxygen to the lens. That’s true whether the cause is vitreous liquefaction or the vitreous gel has been removed.The work suggested that some retinal diseases may protect patients from cataracts. For example, patients who had retinal surgery for complications of diabetes had significantly lower levels of oxygen near the lens. They plan a follow-up study of whether diabetic patients are somehow protected from cataracts.They also note that researchers in Japan have performed retinal surgery without removing the vitreous gel. The surgery is more difficult to do, but the Japanese team found that when the vitreous gel remains intact, retinal surgery patients don’t develop nuclear cataracts to the same extent. Dr. Holekamp isn’t proposing that retinal surgeons stop doing vitrectomies, but she says lowering oxygen concentrations in the fluid that replaces the vitreous gel might help protect the lens. She and her colleagues plan to investigate methods to do so.....“Perhaps we could replace the vitreous gel with a gel polymer that would keep oxygen away from the lens,” he says. “Now that we’re beginning to get an idea of how the vitreous gel works, it may be possible to design interventions to protect the lens both in people who have had a vitrectomy and in those whose vitreous is degenerating as a part of normal aging.”
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Posted by mehdi khanlari at May 29, 2005 11:58 PM