Drugs such as Ozempic, Wegovy and Mounjaro also known as semaglutide and tirzepatide are the types of medication that help to manage severe obesity conditions and also helps to control the sugar levels in blood. Collectively they are known as GLP-1 agonists, these drugs mimic the hormone GLP-1. This limits both hunger and interest for food and helps the users to lose weight. In 2023, prescriptions for GLP-1 drugs like semaglutide and tirzepatide surpassed 40 million worldwide, with billions of dollars in global sales. Their rapid adoption not only reflects their medical benefits but also the cultural conversation around weight loss and metabolic health. Two new studies published today show that people taking these drugs may have a small increased risk of serious eye conditions and vision loss.

Here’s what you need to know if you’re taking or considering these medications.

What damage can occur?

Non-arteritic anterior ischaemic optic neuropathy, or NAION, is a rare but devastating eye condition that occurs when blood flow to the optic nerve is suddenly reduced or blocked. It’s also called an “eye stroke”. Scientists believe that improper flow of blood in the tiny vessels to the optic nerve can be the reason for NAION. The complications included with this are diabetes, hypertension, sleep apnea, smoking, and high cholesterol. There are some anatomical factors, like a small or ‘crowded’ optic nerve head, also provide NAION risks to patients.

The exact cause of NAION remains unclear and there are no current treatments available. People with diabetes are at increased risk of developing NAION.

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Unlike other eye conditions that develop gradually, NAION causes a sudden & painless loss of vision. Patients typically notice the condition when they wake up and discover they’ve lost vision in one eye. Vision tends to worsen over a couple of weeks and slowly stabilises. Recovery of vision is variable, but around 70% of people do not experience improvement in their vision.

What has previous research shown?

A previous study from 2024 found participants prescribed semaglutide for diabetes were four times more likely to develop NAION. For those taking it for weight loss, the risk was almost eight times higher.

In June, the European Medicines Agency concluded NAION represented a “very rare” side effect of semaglutide medications: a one in 10,000 chance. In a first for medicines regulators, the agency now requires product labels to include NAION as a documented risk. In the U.S., the FDA has also been monitoring post-marketing reports of NAION and other ocular complications. While no warnings currently exist, clinicians are encouraged to monitor visual symptoms closely in patients on GLP-1 drugs.

However the recent studies suggest the risks may be lower than we first thought.

In addition to NAION, there is also evidence to suggest GLP-1 drugs can worsen diabetic eye disease, also known as diabetic retinopathy. This occurs when high blood sugar levels damage the small blood vessels in the retina, which can lead to vision loss. Experts suggest that while there is relatively low risk, the absolute numbers are clinically meaningful given the millions of people now taking GLP-1 drugs. For example, even a 0.04% risk translates into thousands of potential cases globally.

It may sound counter-intuitive, but rapid blood sugar reductions can also destabilise the fragile blood vessels in the retina and lead to bleeding.

What do the new studies say?

Two newly published studies investigated people with type 2 diabetes living in the United States over two years. The studies looked at the medical records of 159,000 to 185,000 people.

One study found semaglutide or tirzepatide was associated with a more risk of developing NAION than previously thought. Of 159,000 people with type 2 diabetes who were taking these drugs, 35 people (0.04%) developed NAION, compared with 19 patients (0.02%) in the comparison group.

The researchers also found an increased risk of developing “other optic nerve disorders”. However, it’s unclear what kind of optic nerve disorders this includes, as the medical record codes used didn’t specify.

In contrast, the second study did not find an increased risk of NAION among those taking GLP-1 drugs.However, the researchers found a small increase in the number of people developing diabetic retinopathy in those prescribed GLP-1 drugs.

But overall, participants on GLP-1 drugs experienced fewer sight-threatening complications related to their diabetic retinopathy and required less invasive eye treatments compared to the group taking other diabetes medications.

Further studies are still needed to understand how GLP-1 drugs can lead to eye complications. A current, five-year clinical trial is studying the long-term effects of semaglutides and diabetic eye disease in 1,500 people, which should tell us more about the ocular risks in the future.

What does this mean for people taking GLP-1 drugs?

NAION is a serious condition. But we need to strike a balance between these (and other) risks and the benefits of GLP-1 medications in diabetes care, obesity treatment, reducing heart attack risks and extending lives.

The key lies in informed decision-making and identifying different levels of risk.

People with multiple NAION risk factors – such as sleep apnoea, high blood pressure and diabetes – should undergo careful consideration with their treating doctor before starting these medications.

“Crowded” optic nerve heads are also a risk factor for NAION. This is an anatomical feature where blood vessels at the optic nerve head are tightly packed together. People with crowded optic nerve heads should also undergo careful consideration before starting GLP-1 medications. Additionally, there are benefits of GLP-1 agonists including, reduction in cardiovascular conditions, helping in weight loss, and improving diabetes control—may still outweigh these risks for most patients. The key is shared decision-making between patients and doctors, balancing the metabolic benefits against potential ocular complications.

Although NAION can strike without warning, regular comprehensive eye examinations with your optometrist or ophthalmologist are important. They can detect other drug-related eye problems, including worsening diabetic retinopathy, and can identify patients with crowded optic nerve heads. Patients should report any sudden vision changes. Annual dilated eye exams are especially critical for people with diabetes on GLP-1 therapy.

Emerging research also suggests that improving your heart health might help to reduce risks of developing NAION. This includes proper management of high blood pressure, diabetes and cholesterol – all conditions that compromise the small blood vessels feeding the optic nerve.

Studies also show patients with heart conditions who rely on their medication prescriptions have lower risks of NAION than those who don’t.

Doctors should discuss NAION risks during prescribing and work with eye care providers to monitor regularly for diabetic eye disease.

Aggressive treatment of sleep apnoea and other heart conditions may also help reduce NAION risks.

In recent times, there remains an ongoing need for more research to understand how GLP-1 medications can affect the eye. More clarity is expected within the next 3–5 years. The findings will shape not only how GLP-1 drugs are prescribed but also how ophthalmologists and endocrinologists collaborate to protect vision while treating metabolic disease.

Sources https://theconversation.com/ozempic-and-other-weight-loss-drugs-linked-to-rare-but-serious-eye-conditions-262874

https://www.business-standard.com/health/ozempic-other-weight-loss-drugs-tied-to-rare-serious-eye-issue-study-125081200778_1.html