Can blockbuster weight loss drugs affect your eyes? Here’s what new studies have found

Researchers focussed on how these drugs were linked to diabetic retinopathy (a condition where high blood sugar levels damage the tiny blood vessels in the retina and can cause blindness) and NAION (Non-arteritic Anterior Ischemic Optic Neuropathy, a condition where blood flow to the nerve reduces, leading to sudden, painless vision loss).

What do the studies say?

The first study looked at data of people with Type 2 diabetes on any GLP-1 medicine (including older molecules such as dulaglutide and liraglutide) and compared it with people on other diabetes medications. During the two-year follow-up, the researchers found that the risk of both diabetic retinopathy and NAION was higher in those taking GLP-1 medicines.

The good news, however, was that these medicines were linked to a lower all-cause blindness and lower rate of the sight-threatening complications of diabetic retinopathy such as bleeding in the space between the lens and retina of the eye or a severe form of eye condition where blood vessels grow abnormally in the eye. In patients with diabetic retinopathy, the use of the medicine did not lead to progression to advanced stages. The researchers also noted a reduced need for medical, surgical, or laser-based treatments for these conditions.

The second study compared the patients who were on the strongest GLP-1 medicines like semaglutide and tirzepatide with those on any other diabetes medicines including insulin, metformin, or even the older GLP-1 medicines. During the two-year follow-up period, the researchers noted a slight increase in cases of NAION and other optic nerve disorders.

Why were the studies conducted?

The studies were conducted to verify concerns about diabetic retinopathy that were raised nearly a decade ago during the initial trials of semaglutide. This prompted heightened scrutiny for eye diseases and led to the exclusion of high-risk individuals from further trials. More recently, a study from a single centre showed an increase in incidence of NAION in patients on semaglutide. This prompted further studies to understand the impact of these medicines on the eye.

The European Medicines Agency now says that NAION is an extremely rare adverse reaction that may affect one in 10,000 people who are on semaglutide. Similar studies would now be needed for tirzepatide as well.

Should you continue taking your prescription?

Yes. The researchers say while there is some increased risk of these eye conditions, the GLP-1 medicines themselves have been transformative when it comes to diabetes and obesity management. There is also evidence coming in to show the benefit of these medicines on heart, kidney, and liver conditions linked to diabetes and obesity.

What needs to be done?

Researchers say patients should be informed about the risk of eye conditions when they are prescribed the drugs. They suggest that people who already have diabetic retinopathy should undergo close ophthalmic monitoring when the drugs are initiated or when the doses are increased. They recommend that the medicines be gradually upgraded to avoid sudden swings in blood glucose levels that can affect the eye. For this purpose, they suggest a collaboration between diabetologists and eye specialists. The researchers have further suggested that parameters for eye safety be made a part of all future GLP-1 medicine trials.