Being prescribed semaglutide, the active ingredient in Ozempic and Wegovy, increases a person’s chance of developing a sight-threatening condition, a Harvard study published on Wednesday found.

Non-arteritic anterior ischemic optic neuropathy (NAION) occurs when the optic nerves in the eyes are damaged due to insufficient blood flow, causing vision loss.

NAION is the second most common optic neuropathy condition with the first being glaucoma.

“You can reasonably consider it as a stroke of the optic nerve. And, like a stroke, you lose function,” the study’s senior author, Dr. Joseph Rizzo III, professor of ophthalmology and director of the neuro-ophthalmology service at the Harvard teaching hospital Massachusetts (Mass) Eye and Ear, told The Epoch Times.

He said that his study makes “a strong case for an association between” the development of NAION and semaglutide prescription.

In diabetic patients not prescribed semaglutide, less than 2 percent developed NAION while around 9 percent prescribed semaglutide developed the condition.

In obese or overweight patients not prescribed semaglutide, less than 1 percent developed NAION. In the semaglutide group, less than 7 percent developed NAION.

Semaglutide is a GLP-1 receptor agonist. The drug mimics the effects of GLP-1 hormones naturally present in the body and binds to the GLP-1 receptor to reduce blood sugar and appetite, and causes a host of reactions to cause weight loss and improve diabetes.

The mechanisms of GLP-1 receptor agonists are still not well understood.

While the study found that semaglutide prescription is linked to an over four-fold chance of NAION development in diabetic patients, in people who took semaglutide to treat obesity, prescription of the drug was linked to a more than seven-fold chance of NAION occurrence.

It is still unclear why semaglutide is associated with higher incidences of NAION, Dr. Rizzo said. One major reason for this is that NAION is a highly mysterious disease that doctors, even now, do not know its cause.

People who develop NAION in one eye have a moderate risk of also developing the condition in their other eye.

Dr. Dean Cestari, one of the study authors, said that patients experience varying severities of vision loss, and a third may recover their vision.

The presumption is that NAION occurs due to vascular insufficiency, meaning that the blood vessels supplying the optic nerves are not working properly.

Dr. Rizzo highlighted that NAION is a separate condition from retinopathy, and in the case of diabetic retinopathy, the mechanism is better understood.

Diabetic retinopathy occurs when the retina, which is a layer of tissue that lines the back of the eye, becomes damaged from insufficient blood flow. High blood sugar can cause blood vessels to become inflamed, restricting blood flow.

“My group are all neuro-ophthalmologists,” Dr. Rizzo said. “We were just talking amongst ourselves that I had just seen a patient with NAION who was on Ozempic, and then one of the residents commented that she had just seen one … and then I saw a third one the following week or so, and that coincidence just seemed too unusual.”

However, he highlighted that while his study determined a strong association between semaglutide and NAION, it did not explore causation.

“We don’t know if it’s the medication itself or if these are the patients that are at the highest risk [of developing NAION],” Dr. Cestari said. Dr. Rizzo told The Epoch Times he doesn’t want people to get overly concerned.

“Our findings should be viewed as being significant but tentative, as future studies are needed to examine these questions in a much larger and more diverse population,” he said in the press release.

“This is information we did not have before and it should be included in discussions between patients and their doctors, especially if patients have other known optic nerve problems like glaucoma or if there is preexisting significant visual loss from other causes.”