We have written a great deal at this blog and at our sister blog, Childhood Obesity News, about GLP-1 receptor agonists, also known as GLP-1 drugs, and by scientific names — semaglutide, liraglutide, and tirzepatide — and by brand names: Ozempic, Wegovy, Mounjaro, and Zepbound.

Developed from the saliva of a gila monster lizard, GLP-1 drugs slow digestion, making people feel full sooner and, as a result, they consume less food. The drugs were developed as a treatment for Type 2 diabetes and exenatide was first approved for prescription by the U.S. Food and Drug Administration (FDA) 20 years ago, in 2005.

Noticing that the major benefits of using GLP-1 drugs came from weight loss and that the side effects, mostly nausea, seemed to be tolerable, drug manufacturers expanded their trials and, in 2014, Saxenda (liraglutide) was approved by the FDA for obesity. Other obesity drugs include Wegovy (semaglutide) — approved in 2021 — Trulicity (dulaglutide), and Bydureon (exenatide).

Now that these drugs have been prescribed millions of times, we have anecdotal evidence and some clinical evidence, that they work well against substance use disorders, including nicotine use disorder, alcohol use disorder, and opioid use disorder, as well as behavioral disorders including eating addiction, gambling addiction and internet addiction.

The ways in which GLP-1 drugs work is somewhat mysterious. The obvious impact is on the gut, with studies finding nearly half of users quit in the first year. A major factor in quit rates, however, is the cost of the drugs, which run $800 – $1200 per month without some subsidy. The main physical side effect is nausea, vomiting and diarrhea. It’s like it’s impossible to overindulge and, if you do, it makes you sick.

There is some concern about the psychological side effects of GLP-1 drugs. However, the weight loss associated with the use of GLP-1 drugs also has a positive psychological impacts. Users report feeling better about themselves. A reduction in the desire for pornography (and possibly sex) is offset by a feeling of being more attractive and healthier due to the weight loss.

Now, for the first time, we have a report from JAMA Ophthalmology about a potentially serious side effect of using GLP-1 drugs: sudden vision loss. Researchers from around the United States, led by Dr. Bradley J. Katz, a neurologist at the University of Utah, examined nine cases of “patients experiencing an ophthalmic complication in association with the use of semaglutide or tirzepatide.”

While they could not establish a causal connection between use of the drugs and blindness, they did conclude:

[T]hese findings cannot rule out the possibility that rapid correction of hyperglycemia may be associated with the results reported.

Emily Joshu, health and wellness reporter for The Daily Mail UK, has an explanation for what might be causing the sudden change in vision:

Several studies have linked the shots to conditions that cause inflammation and block blood flow to the eye, causing severe and sometimes permanent vision loss.

Joshu suggests that the drugs cause a sudden drop in blood sugar, potentially damaging blood vessels. A news release published by the American Academy of Ophthalmology in July of last year, recommended to GLP-1 users, “If you take semaglutide and have a sudden loss of vision, stop taking the drug and see a doctor immediately.”

Seven of the nine patients reviewed by researchers were diagnosed with nonarteritic ischemic anterior optic neuropathy (NAION), a condition that causes a blockage in the blood flow going to the optic nerve, leading to sudden vision loss. Joshu describes the condition:

NAION occurs in about 6,000 Americans every year, and it’s most common in patients with diabetes, high blood pressure, and sleep apnea, as these conditions can damage blood vessels.

In most of these cases, the vision returned to normal within a few weeks or months after stopping GLP-1 drugs.

This is a very concerning side effect. People who are taking GLP-1 drugs and have experienced sudden vision loss are advised to stop taking the drug and contact their physician immediately for further guidance. You can bring this article with you, to help your doctor evaluate the potential cause of the problem.

Written by Steve O’Keefe. First published February 18, 2025.

Sources:

“Ophthalmic Complications Associated With the Antidiabetic Drugs Semaglutide and Tirzepatide,” JAMA Ophthalmology, January 30, 2025.

“More Ozempic patients go BLIND as doctors sound alarm over side effect,” The Daily Mail UK, February 10, 2025.

“American Academy of Ophthalmology and North American Neuro-Ophthalmology Society Issue Advice on Weight Loss Drug and Eye Health,” American Academy of Ophthalmology, July 8, 2024.

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