There is not enough evidence to say whether screening adults without vision problems for glaucoma has any clear benefit, according to a government-backed panel.
Between 2 and 4 million people in the U.S. have the degenerative eye condition, which occurs when there is damage to the optic nerve fibers that run between the eye and the brain.
In its new recommendations, the U.S. Preventive Services Task Force (USPSTF) says there are not enough data showing tests for glaucoma are accurate and that treating early glaucoma ultimately prevents vision loss and improves quality of life.
"At this point, probably the most critical gap in the evidence is an approach to screening that actually works," said Dr. Virginia Moyer, chair of the Task Force from Baylor College of Medicine in Houston.
She said a full-on eye exam that could adequately detect early signs of glaucoma takes a long time and is "way too complicated for a primary care appointment."
In looking over past studies, the USPSTF found some evidence that treating early glaucoma can reduce the chance people will develop tiny defects in the visual field, which are usually unnoticeable.
One 2007 review showed a 38 percent lower chance of those defects with treatments such as medicated eye drops, compared to sham treatment with a placebo or nothing.
However, there is "inadequate evidence" that treatment for people without symptoms can prevent more serious vision loss and blindness, the panel wrote Monday in the Annals of Internal Medicine.
"It's clear that the treatment can improve the disease," Moyer told Reuters Health. "It's not crystal clear that the treatment of disease before it's noticeable improves the outcome."
What's more, most glaucoma tests available in primary care offices aren't very accurate, according to the USPSTF, and can't discern when vision problems are likely to get worse. That could lead some people who never would have developed advanced glaucoma to be diagnosed and treated unnecessarily.
Dr. Angelo Tanna, a glaucoma researcher from the Northwestern University Feinberg School of Medicine in Chicago, said screening can still be useful when performed by an ophthalmologist.
"I agree, we don't have strong scientific evidence that proves that screening for glaucoma helps," Tanna, who wasn't involved in creating the new guidelines, told Reuters Health.
"But there's very compelling common sense knowledge that screening for glaucoma is a benefit," he added. "There's no question that identifying and treating glaucoma reduces the risk of progressive vision loss."
He pointed to recommendations from the American Academy of Ophthalmology, which call for regular eye exams for adults with frequency varying by age. For example, the group says people younger than 40 should have a comprehensive exam every five to ten years, and those aged 65 and older should be evaluated every one to two years.