A popular class of drugs used to treat Type 2 diabetes may increase the risk of vision problems, a new study suggests, underlining the importance of regular eye exams for anyone with diabetes.
The study is one of the largest to investigate vision loss associated with thiazolidinediones, a group of drugs that includes the well-known medications Actos and Avandia. While the drugs can help to protect against the many complications of diabetes, small trials and case reports had suggested they may increase the risk of macular edema, or swelling in the central part of the retina, which can result in blindness in one or both eyes.
The new study, published in The Archives of Internal Medicine, involved over 103,000 people with Type 2 diabetes who were followed for about a decade. Those who were using one of the medications were found to have a roughly two to three times higher risk of macular edema, though the likelihood of disease was relatively small. About 1.3 percent of people taking one of the drugs developed diabetic macular edema, compared to a rate of 0.2 percent among those who were not on one of the medications. Combining the drugs with insulin, a common practice, seemed to heighten the risk further.
Iskandar Idris, an author of the study and a consultant in diabetes and endocrinology at Sherwood Forest Hospitals Foundation Trust in England, said that people taking one of the drugs would be wise to get their vision checked regularly, especially if they’re also taking insulin or have a history of visual issues. He pointed out that his study showed that taking ACE inhibitors, which are used for hypertension, seemed to have a protective effect. Some other steps that could help reduce the risk of macular edema, he said, were lowering blood pressure and keeping glucose levels in check.
Though there was no way to know for sure why the drugs might damage the retina, it may have something to do with greater sodium and fluid retention or changes in blood vessels, Dr. Idris said. There was also at least one caveat. Because drugs like Actos and Avandia are typically used as second-line agents, the findings could reflect to some extent a greater severity of diabetes in people using them.