Beta-Blockers Tied to Higher Cataract Risk
THURSDAY July 23, 2009 -- Australian researchers are reporting a possible link between widely used beta-blocker drugs and an increased risk of cataracts.
Beta-blockers are used in pill form to reduce high blood pressure and are also applied to the eye to treat glaucoma, a potentially blinding eye disease. The study found an association between both forms of beta-blocker therapy and accelerated cataract formation and a need for cataract surgery, according to the report published July 23 in the British Journal of Ophthalmology by researchers at the Centre for Vision Research at Westmead Hospital in Sydney.
The researchers tracked almost 3,700 Australians aged 49 or older for 10 years, looking at a variety of risk factors for cataract, a condition in which clouding of the lens of the eye reduces vision.
The association with beta-blocker use was seen after taking into account such known risk factors as smoking and steroid use.
The study found a 45 percent increased incidence of cataract formation and a 61 percent higher incidence of cataract surgery among people treated with beta-blockers, either for glaucoma or high blood pressure.
A "possible" association between use of a different class of high blood pressure drugs, calcium-channel blockers, and cataract surgery was seen in the study, but no such association was seen for all other drugs for high blood pressure.
The report adds weight to an existing theory of a link between beta-blockers and cataracts, said Dr. Donald L. Budenz, associate professor of ophthalmology and associate medical director of the University of Miami Bascom Palmer Eye Institute. But it should not affect use of the drugs for either glaucoma or high blood pressure, he said.
Like other forms of glaucoma treatment, topical beta-blocker therapy is designed to reduce the amount of aqueous humor, the fluid in the interior of the eye. Increased fluid pressure in the eye is believed to cause the damage done in glaucoma, in which the optic nerve deteriorates progressively, Budenz said.
"Living cells in the eye lens do not have blood," he said. "Oxygen is delivered by the aqueous humor. The theory is that beta-blockers reduce production of aqueous humor and so reduce delivery of oxygen to the lens, so the lens ages prematurely. This article seems to find further evidence of that."
But the final verdict on the beta-blocker/cataract link is far from certain, Budenz stressed. "There are studies showing no effect of glaucoma drugs on cataract formation," he noted.
The widespread use of beta-blockers should not be affected by the finding because glaucoma is a more direct -- and less treatable -- cause of vision loss than cataract formation, Budenz said.
Cataracts form slowly, he said. "Most people who have cataracts would need surgery eventually," Budenz said. "If there were sure evidence that beta-blockers hasten their development, that would not factor into our algorithm for treating glaucoma."
Cataract surgery, in which the clouded lens is replaced by a clear, artificial lens, can be done in a matter of hours, usually without a hospital stay, he noted.
"I really don't think that this study would affect patient care at this moment unless stronger evidence came out linking the two," said Dr. Vatinee Bunya, assistant professor of ophthalmology at the University of Pennsylvania Scheie Eye Institute.
The finding "should be taken with a degree of caution," she said. "We definitely need more studies."
Anyway, Bunya said, "topical beta-blockers are not the first line of glaucoma treatment for most practitioners. I don't think many ophthalmologists would change their practice based on this."
There's more on cataracts at the U.S. National Eye Institute.
Posted: July 2009
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