Study links weight-loss drugs to serious eye problems

With the arrival of Mounjaro and Wegovy, powered by the blockbuster ingredients tirzepatide and semaglutide, more people in India are turning to them not just for controlling diabetes but also for weight loss. 

But far away from the glittery scene of these drugs, scientists are turning our attention to a less glamorous, and frankly worrying, question: what about the side effects, especially on the eyes?

A new study published in JAMA has raised eyebrows among both doctors and patients. Looking at data from nearly 15 lakh people, researchers found a higher risk of optic nerve disorders among people with diabetes who were on medications such as semaglutide or tirzepatide.

Semaglutide is a medicine that works like a natural hormone in the body called GLP-1. This hormone helps control blood sugar and reduce appetite. It’s used to treat type 2 diabetes, and in higher doses, to help with weight loss. Tirzepatide works like two hormones, GLP-1 and another one called GIP, which together help the body release insulin, control blood sugar, and manage weight.

One of the conditions flagged is a rare but serious one, known as non-arteritic anterior ischaemic optic neuropathy, shortened to NAION. Often described as an “eye stroke,” NAION occurs when blood flow to the optic nerve is suddenly reduced or blocked. The scary part? People usually notice it only after they’ve already lost vision in one eye. There's currently no treatment for it.

Until recently, NAION was thought to be extremely uncommon among people taking these drugs, about 1 in 10,000 patients, according to older research. But this new study paints a different picture: Out of 1,59,000 people with type 2 diabetes taking semaglutide or tirzepatide, 35 developed NAION during the two-year follow-up, that’s about 1 in 2,500. Another 93 patients were diagnosed with other optic nerve disorders. That’s still a low risk, researchers stress, but it’s higher than previously estimated.

The same journal published another large study, this one tracking 1,85,000 people, that looked at the link between GLP-1 drugs and diabetic retinopathy. This condition happens when blood vessels in the retina get damaged, sometimes leading to vision loss.

People on GLP-1 drugs did show a slightly higher risk of developing diabetic retinopathy. But here’s the twist: those on these drugs actually had fewer severe vision-threatening complications and needed less invasive treatments compared to patients on other diabetes medications.

If you’re taking or considering these medications, there's an important takeaway: the overall risk of eye complications is still low, but it’s not zero. Because eye conditions like NAION can’t be reversed, prevention and early detection matter a lot.

Researchers recommend that all diabetes patients on weight-loss drugs, even those without pre-existing eye problems, should have regular eye screenings. This means eye exams should be part of the standard care plan, not just something you do if your vision starts to change.

Scientists are still figuring out how GLP-1 drugs might lead to eye issues. They’re calling for long-term studies to track patients for many years and understand these connections better.

In the meantime, doctors are in a balancing act — weighing the high cost of GLP-1 drugs against their benefits in controlling blood sugar and reducing diabetes complications, while also keeping an eye (literally) on potential risks.