Ozempic® and the risk of blindness: what's the real story?

An in-depth look at the recent research on semaglutide and NAION

Introduction

Ozempic® and Wegovy® (active ingredient: semaglutide) have long been in the spotlight as effective medications for the treatment of type 2 diabetes and for weight loss. However, concern has recently been raised by news reports and a recent study published in JAMA Ophthalmology suggesting a possible link between semaglutide and a rare eye disease (non-arteritic anterior ischemic optic neuropathy, or NAION) that can lead to blindness (1).

But how strong is that evidence, really? And who is at risk? In this blog post, we'll outline the facts and any uncertainties, so you're better informed about the current state of affairs.

What is NAION?

Non-arteritic anterior ischemic optic neuropathy (NAION) is a rare but serious condition also called an optic nerve infarction. It occurs when the optic nerve suddenly receives less blood and oxygen, causing (partial) vision loss in one eye. This usually occurs without pain (2).

Key features of NAION: 

• Sudden decrease in vision in one eye.

• Often painless, although a small group of patients do experience pain.

• Can range from having reduced vision, for example, to severe, permanent blindness.
  
  

The new research: what does it say?

A research team from Harvard University reviewed the medical records of thousands of people who took Ozempic or Wegovy. They compared this group with people who were given other medications (1). The findings suggest that:

1. In people with type 2 diabetes who took Semaglutide, the risk of NAION was about four times higher than in people with type 2 diabetes who took another non-GLP-1 diabetes medication.

2. In people with obesity or overweight (without type 2 diabetes) who used semaglutide, the risk appeared to be even 7.5 times higher.

3. Risk factors: Other factors such as being male, having high cholesterol, and having a white skin color appeared to further increase the risk.

That sounds alarming, but it's important to emphasize that the researchers haven't proven a causal link. This is called a correlation.

What does correlation mean?

A correlation is a connection. For example, people who swim frequently are also more likely to use sunscreen. This doesn't mean swimming requires sunscreen; the sun plays a role. Similarly, we don't yet know whether semaglutide directly causes NAION or if other factors are involved.

Possible explanations and ambiguities

Although the study points to an increased risk, the precise explanation is still unclear. Here are some possible hypotheses (1,2):

1. Rapidly changing blood sugar and blood pressure levels

• Semaglutide lowers blood sugar levels and can lead to weight loss, which can indirectly lower blood pressure and cholesterol.

• Sudden changes in these body functions – such as a rapid drop in blood pressure, fluctuations in blood sugar levels, and possibly reduced blood flow – can contribute to an increased risk of NAION.

2. Pre-existing increased risk of diabetes and obesity

• People with type 2 diabetes, obesity, high blood pressure, and sleep apnea already have a greater risk of developing eye conditions such as NAION.

• The question remains whether semaglutide further increases this risk or whether this is a coincidence.

3. Research population and selection

• The study was conducted in a single region and involved a predominantly white population. Therefore, the results cannot be easily generalized globally.
  
  

Other explanations and risk factors

There are several factors that can increase the risk of NAION (2):

• Type 2 diabetes

• Obesity

• High blood pressure

• Sleep apnea

• High cholesterol

• Age and gender (in some studies, men were found to be slightly more at risk)

If someone has a combination of these risk factors and is taking Ozempic® or Wegovy®, you may wonder whether the cause is the drug, the underlying conditions, or a combination of both.

Why are we only hearing this now?

Ozempic® and Wegovy® were rigorously tested in clinical trials before they were marketed. No increased risk of NAION was found. It is possible that:

• NAION is so rare that it was not noticed in those relatively small groups of subjects.

• "Real-world" data now provide more insight, as millions of people worldwide use semaglutide. This means that much more data is available than in the initial studies.
  
  

Response from experts and authorities

Both the manufacturer of Ozempic® (Novo Nordisk) and several medical organizations have responded to these findings:

1. American Academy of Ophthalmology (AAO) and North American Neuro-Ophthalmology Society (NANOS) (3)

• They acknowledge that the research suggests a possible link, but emphasize that the study design is not suitable to prove a causal relationship.

• They emphasize that the drug has been extensively tested in several clinical trials and that no increased risk of NAION had previously been identified prior to this study.

• They indicate that patients should not simply stop taking semaglutide and that further research is crucial to gain clarity.

2. European Medicines Agency (EMA) – PRAC Committee (4)

• The EMA's Pharmacovigilance Risk Assessment Committee (PRAC) recently announced that it will thoroughly investigate the findings.

• All available data, such as research results and user experiences after market launch, are examined.

• There is currently no definitive conclusion; the PRAC is expected to make recommendations once the review is completed.

3. Novo Nordisk

• The manufacturer states that NAION has not been identified as a known side effect in previous studies.

• They underline that semaglutide went through very strict controls before it came on the market.
  
  

Is further research being done?

Yes, there will definitely be further research to determine whether semaglutide actually increases the risk of NAION (3). The researchers are looking at various sources for this:

• Post-Market Monitoring: Authorities are collecting and analyzing reports of adverse events as more people use this medicine.

• Comparative studies: Several groups of researchers are now comparing large numbers of people who use semaglutide with people who do not, to see whether NAION is more common in the semaglutide group.

In the meantime, as long as there is no strong evidence that semaglutide actually causes NAION, doctors will generally continue to prescribe it to people for whom the benefits outweigh the potential risks.

What does this mean for you if you use Ozempic® or Wegovy®?

1. Don't just stop taking your medication

• Semaglutide is a very valuable medication for many people. It helps control blood sugar in type 2 diabetes, and it can aid weight loss in obesity.

2. Be aware of your vision

• If you experience a sudden decrease in vision, in one or both eyes, without pain or any other obvious cause, contact a doctor or ophthalmologist immediately.

3. Consult with your doctor

• Are you worried about this news? Discuss it with a doctor or specialist. They can advise you on your treatment.
  
  

Conclusion

Although news reports suggest that Ozempic® and Wegovy® can cause blindness, there is currently no convincing evidence that these medications actually cause NAION. A link has been found, but further studies are needed to determine the cause.

Continue to talk to your doctor, follow the instructions for use, and be alert to any sudden changes in your vision.

Sources: 

1. Hathaway JT, Shah MP, Hathaway DB, et al. Risk of nonarteritic anterior ischemic optic neuropathy in patients prescribed semaglutide. JAMA Ophthalmol. 2024;142(8):732-739. doi:10.1001/jamaophthalmol.2024.2296.

2. Oogartsen.nl. Optic nerve infarction [Internet]. [cited 2025 Feb 22]. Available from: https://www.oogartsen.nl/zenuwen-en-oogkas/oogzenuw-infarction / .

3. American Academy of Ophthalmology. American Academy of Ophthalmology and North American Neuro-Ophthalmology Society issue advice on weight loss drug and eye health [Internet]. 2023 Jul 3 [cited 2025 Feb 22]. Available from: https://www.aao.org/newsroom/news-releases/detail/weight-loss-drug-and-eye-health .

4. European Medicines Agency (EMA). Meeting highlights from the Pharmacovigilance Risk Assessment Committee (PRAC) 13-16 January 2025 [Internet]. 2025 Jan 17 [cited 2025 Feb 22]. Available from: Link to PRAC message .