GLP-1s Cause Blindness?!

Happy Monday!

Today’s email is a direct response to questions I received from several different readers over the last few months.

Most of their questions go like this:

The mainstream media has gone full scorched-earth with headlines like “Weight-Loss Drugs Causing Blindness?” and “New Class of Fat-Loss Medications Linked to Eye Damage.”

These stories spread quickly, mainly because if it bleeds, it leads!

So let’s slow down and take a breath.

Let’s zoom out.

Let’s look at the actual human data.

And then let’s answer this clearly and rationally.

There is a signal in the data, but it is heavily misunderstood.

And the question we should be asking is not “Do GLP-1s cause blindness?” but instead…“What kind of patient population is developing these issues? And what else is going on in their physiology?”

By the end of this email, you will have a full understanding of the actual studies, the magnitude of risk, what is known, what is speculative, and whether healthy individuals using GLP-1 agonists need to worry.

The Rumors

The panic started with a few observational studies showing an association between GLP-1 drugs (mostly Semaglutide and occasionally Tirzepatide) and NAION, a rare condition known as non-arteritic anterior ischemic optic neuropathy.

This condition is often described as an “optic nerve stroke.”

Notice that word.

Stroke.

Not “drug-induced retinal destruction.”

Not “drug melting your optic nerve.”

A stroke of the optic nerve, almost always driven by vascular disease.

The studies found a slightly elevated hazard ratio for NAION in GLP-1 users.

But when you look at the actual numbers, the absolute risk is extremely low.

In one of the most widely shared studies, there were 35 cases out of nearly 80,000 people using these drugs over two years.

Hardly an epidemic.

Every single one of these large studies is observational, retrospective, and overwhelmingly involves patients with type 2 diabetes, hypertension, obesity, and other vascular comorbidities.

In other words, the exact population most likely to develop an optic-nerve stroke in the first place.

But this nuance doesn’t make the headlines.

“Diabetic patients face low but measurable vascular eye risk” doesn’t get clicks.

“Blindness epidemic from weight-loss drugs” does.

The Research

Let’s break down what the research actually found.

One large JAMA Network Open study reported a hazard ratio of ~1.76 for NAION in GLP-1 or dual-agonist users compared to other diabetic medications.

Sounds scary on the surface. But hazard ratios can be misleading without context.

Here is the context:

• Absolute cases: 35 events in 79,699 GLP-1/dual-agonist users

• Population: Nearly all diabetic, overweight, or obese

• Confounding: High likelihood of other vascular and metabolic risk factors

• Study type: Retrospective observational (cannot prove causation)

This is exactly the kind of population already at high baseline risk for optic nerve vascular disease. A healthier, non-diabetic population has not shown the same signals.

Another study found lower rates of “visual issues and blindness” in Tirzepatide users compared to other obesity drugs (hazard ratio around 0.44).

In this case, GLP-1s were actually improving vision outcomes.

In fact, the EMA warning that made headlines applied specifically to Semaglutide, not Tirzepatide, and even that was classified as a “very rare” event.

So the data is inconsistent, observational only, and highly confounded by the patient population being studied.

My Theory

Here’s what I believe is actually happening, based on thousands of real-world patients and the mechanistic pathways involved.

GLP-1 agonists rapidly alter metabolic variables.

Blood sugar can normalize quickly if someone is hyperglycemic.

Weight drops quickly.

Blood pressure and fluid shifts can change quickly.

If someone has underlying vascular disease, especially diabetes-related microvascular damage, this rapid change can temporarily alter perfusion pressure to fragile tissue beds such as the eye.

In rare cases, that risk could manifest as NAION.

But that is not the same thing as GLP-1s causing blindness in healthy people.

The typical user experiencing NAION in the studies is:

• Diabetic

• Hypertensive

• Obese

• Already at elevated risk for microvascular diseases

• Sometimes unmanaged sleep apnea (a major NAION risk factor)

Their underlying metabolic and vascular disease is the real issue.

The drug just happens to be present at the same time, because GLP-1s are now the most widely prescribed diabetic medications on the planet.

This is correlation, not causation, and the data strongly supports this interpretation.

Are Healthy Individuals at Risk?

If you are a healthy, non-diabetic, non-hypertensive individual with no pre-existing vascular eye disease, there is no compelling evidence that GLP-1 agonists pose any meaningful risk to your vision.

No randomized controlled trial has ever shown an increased incidence of blindness.

No mechanism unique to Tirzepatide or Semaglutide has been identified that would selectively injure the optic nerve in healthy individuals.

No ophthalmologic society has issued a warning for healthy, non-diabetic users.

And in contrast to the fear-based headlines, some of the most robust datasets suggest improved ocular outcomes due to improved glucose handling, reduced inflammation, and improvements in vascular function.

The only people showing issues are the exact same people who already experience the highest rates of NAION, maculopathy, and retinal vascular disease.

So if you are metabolically healthy, insulin sensitive, and losing weight predictably, there is no reason to believe you are at increased risk.

If you are diabetic, hypertensive, older, or have sleep apnea, you might want periodic eye exams anyway.

Best Practices

Here is what I recommend for GLP-1 users who want to be proactive for eye and vascular health:

1. Get a baseline eye exam.

   Especially if you are diabetic or have any degree of insulin resistance.

2. Avoid overly rapid titration.

   Jumping from 2.5 mg per week to 12.5 mg per week in eight weeks is a good way to shock your system. Let your physiology adapt.

3. Support mitochondrial and vascular function.

   Agents such as SS-31, MOTS-c, ARA-290, and taurine can improve microvascular health (as documented in studies).

4. Treat sleep apnea if present.

   Untreated apnea is one of the strongest drivers of NAION in all populations.

5. Maintain hydration and electrolytes.

   Rapid weight loss often creates intravascular shifts that can affect perfusion.

6. Do not rely on GLP-1s alone.

   You must be training, performing cardio, sleeping well, and eating whole foods.

When used responsibly, GLP-1s are one of the most powerful metabolic tools ever created.

The risk of serious eye disease for healthy users is not zero. Nothing in biology is zero risk.

But it is extraordinarily low, and the data does not support widespread danger.

Final Thoughts

Headlines are designed to scare you.

The people designing them are not reading hazard ratios, confidence intervals, or diabetic comorbidity tables.

But you want to understand your physiology at a deeper level.

We have a weak observational signal in a high-risk diabetic population for a rare vascular optic event that is already known to occur in those same populations regardless of medication.

We do not have evidence of GLP-1 agonists independently causing blindness in healthy people.

We do not have plausible mechanisms showing direct drug toxicity to the optic nerve.

We do not have randomized data confirming risk.

My theory is that the underlying disease state is the real culprit. GLP-1 use acts as a marker for metabolic dysfunction, not a cause of blindness.

So if someone brings this up at turkey time on Thursday, remind them:

GLP-1s are not blinding healthy people.

Unmanaged metabolic disease blinds people.

Best,

Hunter Williams

Further Reading

• JAMA Network Open study on GLP-1 use and NAION

• University at Buffalo analysis of observational GLP-1 eye study

• QPS analysis of GLP-1-related eye health reports

• Nature study comparing Tirzepatide with other obesity drugs (lower vision-issue risk)

• EMA statement on Semaglutide and rare NAION risk