Study: complementary, alternative meds for glaucoma show no benefit, harm

Baltimore-Complementary and alternative medicine (CAM) is a multibillion-dollar industry in the United States, and the fact that it lacks regulatory oversight creates some cause for concern. However, when it comes to glaucoma, it appears that CAM use is modest and mostly benign, but also backed by little evidence of efficacy, said Derek S. Welsbie, MD, PhD.

Dr. Welsbie noted that the National Center for Complementary and Alternative Medicine of the National Institutes of Health estimates that Americans are spending $34 billion a year on CAM. However, studies of glaucoma patients seen at university-based practices in the United States and Canada found only 5% and 14% of participants, respectively, were using CAM for their disease.

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Across the two studies, megavitamins/antioxidants, bilberry, gingko biloba, carrots, and a topical formulation of n-acetylcarnosine (Bright Eyes) were the most commonly reported CAM agents being used. The prevalence of marijuana usage for glaucoma is difficult to determine accurately, but in two studies, self-reported usage was ≤2%, noted Dr. Welsbie, assistant professor of ophthalmology, The Wilmer Eye Institute, Johns Hopkins School of Medicine, Baltimore.

“The most commonly used CAM agents correspond with the top hits of a Google search for alternative medicine and glaucoma, suggesting patients are turning to the Internet as their leading source of information,” Dr. Welsbie said. “Particularly notable is the fact that the top hits are links to university websites.”

Lack of scientific support

A PubMed search for evidence about the efficacy of the most frequently used CAM agents reveals little to no support that they provide any benefit. Although 15 articles are identified in a search for n-acetylcarnosine and glaucoma, a single individual is the author on all but 1 article, and mentions of ‘ageless vision,’ ‘powerful eye health,’ and ‘all-in-one universal antioxidant’ in the articles titles provides good reason for skepticism about the information they contain, said Dr. Welsbie.

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Discussing bilberry, Dr. Welsbie explained that it is generally used as an extract from the fruit that is similar to blueberry, and the active compound is thought to be anthocyanins. The idea that bilberry has a positive effect on vision dates back to World War II where pilots in the Royal Air Force anecdotally noted ingestion of bilberry jam seemed to improve their night vision. However, results of a study enrolling young healthy men found no differences in various vision tests comparing subjects receiving bilberry and placebo-treated controls.

Results from both a retrospective study and a prospective study including patients with glaucoma show small benefits from treatment with bilberry/anthocyanins, but the data are anything but definitive.

“I would summarize the evidence by saying there is a little data in favor of bilberry use for glaucoma, but clearly more needs to be done,” Dr. Welsbie said.

He similarly concluded that there was little data to support the use of gingko biloba. Dr. Welsbie noted that this extract of the leaf from the gingko biloba tree demonstrates neuroprotective and antioxidant properties in in vitro studies and showed neuroprotectant activity in a rat model of chronic glaucoma. However, in the decade since the latter report was published, there has been no further evidence that gingko biloba is neuroprotective to retinal ganglion cells, and results from two small clinical studies enrolling patients with glaucoma produced conflicting results.

Little cause for concern

Ophthalmologists should know that the Canadian study investigating CAM use among glaucoma patients found it was not disclosed to the ophthalmologist by 75% of users. However, at least for some of the more commonly used agents, there is likely no reason to be worried about concealed use, Dr. Welsbie said.

“For carrots and bilberry, any possible risks are probably small, and while there had been concern that gingko could affect platelet function and interact with other anticoagulants, more recent data indicates that by itself, gingko probably does not cause a significant coagulopathy,” he explained.