Key Takeaways

  • Among patients who developed bilateral NAION, 56.8% of second-eye events in GLP-1 users occurred within 6 months, compared with 40.6% among nonusers
  • The retrospective database study identifies an association and cannot establish that GLP-1 medications cause earlier fellow-eye involvement
  • Researchers said ophthalmologists should consider GLP-1 use when taking medication histories and counseling patients after a first-eye NAION event, while recognizing the systemic benefits of the drugs

Patients taking GLP-1 medications who develop nonarteritic anterior ischemic optic neuropathy (NAION) in both eyes may experience involvement of the fellow eye sooner than patients who are not taking the drugs, according to research presented at the 130th annual meeting of the American Academy of Ophthalmology (AAO).

The study found that among patients who developed bilateral NAION, 56.8% of second-eye events in GLP-1 users occurred within 6 months of the initial event, compared with 40.6% among patients who were not taking GLP-1 medications.

NAION occurs when insufficient blood flow to the optic nerve results in sudden, painless vision loss, typically in one eye. Although the fellow eye can eventually become affected, rapid sequential involvement is less common.

“Approximately 15% of patients will develop NAION in the fellow eye within 5 years after a diagnosis in the first eye,” said Ashley Tin, a study co-author and medical student at Carle Illinois College of Medicine. “Rapid, sequential involvement of the second eye is typically less common.”

The study grew out of a clinical observation by co-author Matthew D. Kay, MD, who noticed several patients presenting over a relatively short period with NAION affecting both eyes in rapid succession—and, in some cases, simultaneously. The patients were taking GLP-1 agonists.

“The apparent increase in rapidly sequential presentations seemed unusual and prompted us to investigate whether this pattern could also be seen in a large national database,” Dr. Tin said.

Investigators used Epic Cosmos, a large repository of electronic health records, to examine second-eye NAION events recorded between 2015 and 2025.

The analysis included approximately 1,440 GLP-1 users and 20,700 patients who were not taking the medications. Researchers examined the timing of fellow-eye involvement following the initial NAION event, ranging from 1 month to 5 years.

Among GLP-1 users who developed bilateral disease, 56.8% of second-eye events occurred within 6 months, compared with 40.6% in the non-GLP-1 group. In the researchers’ statistical model, the shift toward earlier rather than later second-eye events was approximately 1.98 times as strong among GLP-1 users. Investigators reported that the pattern was observed both before and after GLP-1 medications came into widespread use.

“We were not particularly surprised by the findings because the large-database analysis was consistent with the clinical observation that prompted the study,” Dr. Tin said. “That said, seeing the clinical impression reproduced across a very large dataset was striking and underscored the need to investigate the association further.”

Findings do not establish causation

The researchers cautioned that the study identifies an association and does not establish that GLP-1 medications cause earlier fellow-eye NAION.

Patients taking GLP-1 medications had average hemoglobin A1C levels 1.0 to 1.4 percentage points higher than patients who were not taking the drugs. The difference raises the possibility that diabetes severity or other underlying health factors could contribute to the observed association.

The use of aggregated rather than individual patient-level data also limited researchers’ ability to control for potential confounding factors.

For ophthalmologists, Dr. Tin said the findings support including GLP-1 use when obtaining a medication history from patients with NAION and considering it when counseling patients following a first-eye event.

“GLP-1 use should be an important part of the medication history in patients presenting with NAION, particularly when counseling patients after a first-eye event,” Dr. Tin said, adding that treatment decisions “should continue to consider the substantial systemic benefits of these medications.”

Patients should not discontinue GLP-1 therapy on the basis of the findings, she emphasized.

“These drugs have important benefits for diabetes, obesity and cardiovascular health, and our study identifies an association rather than proving that the medications cause NAION,” Dr. Tin said.

The AAO and the North American Neuro-Ophthalmology Society have also issued guidance addressing current evidence surrounding GLP-1 medications and vision loss.

Further research will be needed to determine whether the observed pattern is related to GLP-1 therapy itself or to underlying characteristics of patients who use the medications. Studies using detailed patient-level data could account for diabetes severity and other vascular conditions while examining specific GLP-1 agents, doses, duration of treatment, and the timing of therapy relative to NAION events.

Ultimately, prospective studies will be needed to determine whether the association is causal, according to Dr. Tin.