Research explores how cataracts
by Will SansomJuanita Lopez of San Antonio is one of the more than 20 million U.S. citizens whose vision has been impaired by cataracts. The clouds on the lenses of her eyes took away her confidence to leave home and kept her from enjoying sewing, ceramic painting and other hobbies. She no longer wanted to go fishing with her husband at Braunig and Calaveras lakes near San Antonio. She only felt comfortable at home, away from people and potential obstacles.
In April, Mrs. Lopez underwent cataract removal to regain her quality of life. She is seeing clearly again. But what if research conducted at the Health Science Center could eliminate the need for cataract surgery? "It would be great, better than having surgery," she said.
Jean X. Jiang, Ph.D., associate professor of biochemistry, is studying two proteins that, when abnormal, keep many eye lens cells from forming properly. The proteins, connexin 50 and connexin 46, are supposed to promote cell-cell communication through "gap junctions," which are channels between cells. This intracellular dialogue is vital to having a healthy lens.
"The lens is supposed to be crystal clear," Dr. Jiang said. "Poor communication in gap junctions results in formation of cataracts. This is harmful because the lens is the window of the eye, focusing light on the retina in the back of the eye. If the lens is clouded, less light gets to the retina and vision is blurred."
She has a four-year, $1.2 million grant from the National Eye Institute to study
the "talking" going on at gap junctions, which maintain the transparency and clarity of the lens. She hopes that one day the research will lead to medications
to treat the biochemical cause of cataracts and possibly put an end to the need for cataract surgery.
"When a patient develops a cataract, we take it out and insert an artificial lens," said Carlos A. Rosende, M.D., assistant professor of ophthalmology at the Health Science Center. "The artificial lens is placed through a small incision after the cataract has been broken up and aspirated. Occasional complications include inflammation, infection and problems with the lens placement. So we have a way around cataracts, but obviously having no surgery would be better, especially for older patients, who are generally the ones who have cataracts."
Cataracts are a leading cause of blindness worldwide. Cataract removal is the most commonly done surgical procedure in this country, but is not widely available in Third World countries.
"A connexin protein treatment might do to cataract surgery what tuberculosis screening, surveillance and effective antibiotics did to sanitoriums," Dr. Rosende said. "The societal and economic ramifications would especially be felt in the developing world, where eye care is lacking."
Dr. Jiang is using a chicken model to learn more about the lack of cell-cell communication when connexin proteins are out of kilter. She has found it is possible to closely model the roles of connexins in actual eye lens formation.
Her studies may result in changing the standard of care for the Juanita Lopezes of the future and may lead to medications to clear the window of the eye.
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