A new study adds to evidence to suggest the main ingredient in Novo Nordisk’s injectable drug for type 2 diabetes may increase patients’ risk for a dangerous eye condition.

The findings about the NOVOb.CO injectable GLP-1 drug are included in JAMA Ophthalmology, published on Thursday.

The researchers tracked nearly 175,000 patients with diabetes who received semaglutide – the active ingredient in Ozempic and other Novo products – and the same number of patients with diabetes who received non–GLP-1 drugs.

The higher risk of developing the sight-threatening eye problem known as nonarteritic anterior ischemic optic neuropathy, or NAION, did not appear during patients’ first year of treatment with semaglutide.

But their risk for NAION was more than doubled after two years of treatment, compared to patients taking diabetes medicines from other classes.

In subgroup analyses, the elevated risk for NAION associated with semaglutide was confined to women and to patients taking Ozempic, which is only one of Novo’s semaglutide products.

Patients with diabetes who received Rybelsus, an oral semaglutide, or Wegovy, which is injected like Ozempic and approved for obesity, had no increased risk for NAION compared with those who received non–GLP-1 medications.

A small study published last year and a separate large study published last month had similarly found that adults with type 2 diabetes using semaglutide had a higher NAION incidence rate than when they were not using the medication.

The authors of the new report note that retrospective studies such as these cannot prove causation.

“Because NAION is a potentially debilitating ophthalmic condition, gaining a clearer understanding of its incidence and the factors influencing its occurrence would enhance care for those considering the use of these medications,” they said.