GLP-1 Vision Loss

Losing vision is not like most injuries. There is often no warning, no pain and no obvious explanation — one morning part of the visual field is simply gone, and it does not come back. If that happened to you while you were taking a GLP-1 medication, you are almost certainly asking whether the two are connected.

That is a fair question, and it is now being asked in a federal court. Lawsuits pending before one judge allege that the makers of certain GLP-1 receptor agonist medications failed to warn patients and prescribers that the drugs could cause non-arteritic anterior ischemic optic neuropathy (NAION), a form of sudden vision loss. The manufacturers dispute the allegations, including whether these medications are capable of causing the injury at all5.

GLP-1 medications and vision loss

GLP-1 receptor agonists are a class of medications prescribed for type 2 diabetes and for chronic weight management. The class is not interchangeable. Different medications in it contain different active ingredients, were approved at different times, and carry different bodies of research behind them.

The vision-loss concern in the published research has focused on semaglutide, the active ingredient sold under the brand names Ozempic, Wegovy and Rybelsus. The federal litigation reaches further than that. The court has described the proceeding as involving GLP-1 receptor agonists and GLP-1/GIP dual receptor agonists sold under the brand names Ozempic, Wegovy, Rybelsus, Saxenda, Trulicity, Mounjaro and Zepbound — the first four made by the Novo Nordisk defendants, the last three by Eli Lilly and Company10.

That gap between where the published research points and how widely the litigation is drawn is worth understanding before you read anything else on this page. The studies below examine semaglutide. The MDL examines a broader group of GLP-1 medications, and whether each of them can cause NAION is one of the questions the court has not yet answered.

Observational research can identify an association. It cannot, on its own, establish that a medication caused one person’s vision loss.

Every study discussed on this page says so in its own conclusions. That is not a reason to dismiss the research, and it is not a reason to assume the research settles anything. It is the reason individual cases have to be examined individually — by the facts of one prescription history and one medical chart, not by a headline.

What is NAION?

NAION stands for non-arteritic anterior ischemic optic neuropathy. It is a condition in which part of the optic nerve is damaged because it does not receive enough blood flow48.

How NAION typically presents

Sudden onset

Vision loss generally comes on abruptly rather than gradually, and is often first noticed on waking.

Usually painless

There is typically no pain in or around the eye, which is one reason people delay seeking care.

Usually one eye

NAION generally affects one eye, although the other eye can be affected later8.

Often permanent

There is no treatment established to reverse the damage, and vision that is lost frequently does not return8.

This is a plain-language summary of how a condition is described in the medical literature, not a diagnosis and not medical advice. Whether a particular episode of vision loss was NAION is a question for the clinicians who examined the eye.

Sudden vision loss is a medical emergency. If your vision changes suddenly, seek prompt medical attention — an emergency department, an ophthalmologist or your own physician — rather than waiting to see whether it improves. Nothing on this page should delay that call.

Why is semaglutide being studied?

Because clinicians noticed something, published it, and other researchers went looking. The sequence is short and it is on the public record:

1. In 2024, researchers at Massachusetts Eye and Ear and Harvard Medical School published a retrospective matched cohort study in JAMA Ophthalmology. Working from a registry of 16,827 patients seen by neuro-ophthalmologists at a single academic institution, they reported an association between prescribed semaglutide and NAION, and described the finding as a basis for further investigation rather than a demonstration of cause1.
2. In 2025, larger observational studies followed, drawn from national databases rather than one institution. They have not all pointed the same way or produced the same effect size — one large cohort study of patients with diabetes reported an increased risk of NAION emerging over a period of years, while noting that a retrospective design can infer association and not causation2.
3. In June 2025, the European Medicines Agency’s safety committee completed its own review and concluded that NAION is a very rare side effect of semaglutide medicines, occurring in up to 1 in 10,000 people who take them. European product information for those medicines was updated to list it34.
4. Through 2025 and 2026, the research has continued in both directions — additional cohort studies, systematic reviews and commentary — and the question of whether these medications cause NAION remains open in the scientific literature9.

Read together, that record supports a specific and limited statement: a possible association has been identified, regulators outside the United States have treated it as a very rare adverse effect, and the underlying causal question has not been closed. Any page that tells you more than that is telling you more than the evidence does.

A developing medical timeline

Semaglutide, NAION and the courts

1. December 2017

   The U.S. Food and Drug Administration approves semaglutide injection for the treatment of type 2 diabetes in adults, as an adjunct to diet and exercise7.

2. July 2024

   JAMA Ophthalmology publishes the Massachusetts Eye and Ear cohort study reporting an association between prescribed semaglutide and NAION1.

3. 2025

   Larger observational studies using national databases examine the same question and report varying effect sizes, each noting the limits of a retrospective design2.

4. June 2025

   The European Medicines Agency’s Pharmacovigilance Risk Assessment Committee concludes that NAION is a very rare side effect of semaglutide medicines and recommends adding it to the European product information3. The World Health Organization relays the conclusion the same month4.

5. December 2025

   The Judicial Panel on Multidistrict Litigation centralizes the federal GLP-1 vision loss cases in the Eastern District of Pennsylvania before U.S. District Judge Karen S. Marston as MDL No. 31635.

6. 2026

   Research continues to be published, including a nationwide cohort study of United States veterans with type 2 diabetes in JAMA Ophthalmology9, while the federal litigation moves through discovery on general causation.

A timeline is not a causal argument. These are the dated, verifiable events behind the current state of the question — regulatory, scientific and procedural — set out so you can see what has actually happened and what has not.

Signs and symptoms associated with NAION

People who have experienced NAION commonly describe some combination of the following. They are the changes worth mentioning to a clinician, and worth mentioning to us:

• Sudden loss or reduction of vision
• Vision change that is usually painless
• Loss of part of the visual field
• Blurred or dimmed vision
• Reduced contrast or color perception
• Changes first noticed on waking

Sudden vision loss is a medical emergency. Seek medical attention first; the legal question can wait a day.

The federal GLP-1 vision loss litigation

In re: Glucagon-Like Peptide-1 Receptor Agonists (GLP-1 RAs) Non-Arteritic Anterior Ischemic Optic Neuropathy (NAION) Products Liability Litigation — MDL No. 3163

Federal lawsuits alleging NAION after the use of GLP-1 receptor agonist medications have been centralized in the U.S. District Court for the Eastern District of Pennsylvania before U.S. District Judge Karen S. Marston, who also presides over the separate GLP-1 proceeding concerning gastrointestinal injuries5.

An MDL, or multidistrict litigation, allows federal cases sharing common questions of fact to be coordinated before one judge for pretrial proceedings6. It is not a class action, individual plaintiffs keep their own claims, and the creation of an MDL establishes nothing about whether the allegations are true.

The common factual questions identified in this proceeding concern5:

• The development, manufacture and testing of the medications at issue
• Their regulatory history, promotion and labeling
• Their capacity to cause NAION
• Whether the warnings given to patients and prescribers were adequate

The plaintiffs assert claims for failure to warn, design defect and breach of warranties5. The litigation is at the pretrial stage; no court has decided whether these medications can cause NAION.

The proceeding is young and, by mass tort standards, small. The court counted 137 cases in it on June 15, 2026, nineteen of them against the Eli Lilly defendants10. In July 2026 the court decided to take up two threshold questions first — whether these medications are capable of causing NAION at all, and whether the plaintiffs’ warning claims are blocked by federal drug labeling law — rather than working up individual cases in parallel10. It also appointed a retired federal judge as Special Discovery Master to hear discovery disputes in the first instance11.

What if this happened to you?

You do not need to have worked out the science, the litigation or your own medical history before you call. It helps to think about four things:

What we ask on the first call

Which medication, and when

The name if you remember it, the approximate dates you took it, and who prescribed it. Proof of use — a pharmacy record, a prescription, a refill history — is one of the two things this litigation turns on.

What happened to your vision

Which eye, how suddenly, what you noticed and what you could no longer see.

What you were told

The diagnosis, approximately when it was made, and the clinician who made it. Proof of diagnosis is the other thing this litigation turns on.

Your health history

Other conditions, other medications and any prior eye problems. Defendants will examine all of it, so we would rather understand it early.

Don’t try to decide what matters before you call. Tell us what happened, and we’ll ask the questions needed to understand it.

Medical records that may help tell the story

Depending on the circumstances, the records that help document a GLP-1 prescription history and a vision-loss diagnosis may include:

• GLP-1 prescription and pharmacy records
• Primary-care records
• Endocrinology records
• Weight-management or bariatric program records
• Ophthalmology records
• Neuro-ophthalmology records
• Emergency department or urgent-care records
• Vision tests and imaging, including visual fields and OCT
• Records documenting the initial onset of symptoms
• Health insurance explanations of benefits

If you have none of these, that is not a reason to wait. Much of it can be requested on your behalf once we know where you were treated.

Health insurance and ongoing care

Vision loss rarely involves one appointment. It can mean an emergency visit, a referral to a neuro-ophthalmologist, repeat visual-field testing, imaging, monitoring of the unaffected eye and, for some people, low-vision rehabilitation, changes to driving and changes to work.

All of that generates paperwork, and the paperwork is worth keeping. Explanations of benefits, denial letters, referral authorizations, bills and appeal correspondence together document the course and the cost of care in a way that memory cannot. Coverage questions themselves belong with your insurer or your provider — but bring the letters to us if they are not clear.

You tell us what happened. We take it from there.

People who lose vision suddenly spend the following months being handed information rather than answers — a diagnosis in unfamiliar words, a prognosis that is hedged, and advice from every direction about what they should do next. You should not also have to become an expert in neuro-ophthalmology or federal procedure just to find out whether what happened to you deserves a closer look.

At CBW Law, we use modern technology and case-management systems to handle complex litigation efficiently, but the reason those systems exist is simple: so our team can focus on the people behind every case.

We listen. We investigate. We order the records. And when the facts support a case, we are prepared to pursue it for the long haul. Tell us your story.

Plain English

Medical, Health & Insurance

A claim like this arrives wrapped in two vocabularies, neither of them yours: the clinical language in your eye-care chart, and the coverage language in the letters from your health plan. Here is what some of the terms you may encounter mean, so the paperwork is readable before it becomes decisive.

The medications

GLP-1 receptor agonist

A class of medications that act on the glucagon-like peptide-1 receptor. They are prescribed for type 2 diabetes and for chronic weight management, and the class includes several different active ingredients sold under several different brand names5.

Semaglutide

One active ingredient within the GLP-1 class, sold under the brand names Ozempic, Wegovy and Rybelsus. It is the ingredient the published NAION research has focused on13.

The eye and the injury

NAION

Non-arteritic anterior ischemic optic neuropathy: damage to the front portion of the optic nerve caused by insufficient blood flow, typically producing sudden and usually painless vision loss in one eye48.

Optic nerve

The nerve that carries visual signals from the eye to the brain. Damage to it cannot be corrected with glasses, because the problem is in the transmission rather than in the focusing.

Ischemia

A reduction in blood flow to tissue, and therefore in the oxygen that blood carries. The ischemic in NAION refers to this.

Visual field

The full extent of what an eye can see, including everything outside the point being looked at directly. NAION characteristically removes part of it while leaving the rest, which is why the loss is sometimes described as a missing region rather than as general blurring.

Visual acuity

The sharpness of central vision, usually reported as the familiar fraction from an eye chart. Acuity and visual field are different measurements, and an eye can lose one while retaining much of the other.

The clinicians and the coverage

Ophthalmologist

A physician who specializes in the medical and surgical care of the eyes.

Neuro-ophthalmologist

An ophthalmologist or neurologist with additional training in conditions affecting the visual pathway between the eye and the brain, including the optic nerve. NAION is often diagnosed or confirmed by one.

The paperwork worth keeping

Organized copies of pharmacy records, insurance correspondence, explanations of benefits, medical bills and referral authorizations can make it easier to establish both the prescription history and the course of care.

A denied service

If coverage for a service is denied, the denial notice generally contains the insurer’s reason and the available review or appeal procedures. Coverage questions should be addressed with the insurer, the provider or another qualified professional.

Educational only. These are plain-language summaries of words that turn up in charts, letters and bills — not clinical definitions, not medical advice, not a diagnosis of anyone, and not a description of what any particular policy covers. For what a diagnosis means for you, ask the clinician who made it. For what your plan covers, read the plan, and bring it to us if it is not clear.

Questions

Frequently asked GLP-1 vision loss questions

The questions callers actually open with, answered the way we would answer them on the phone.

What does GLP-1 mean?

GLP-1 stands for glucagon-like peptide-1. A GLP-1 receptor agonist is a medication that acts on the receptor for that hormone; the class is prescribed for type 2 diabetes and for chronic weight management5.

It is a class, not a single drug. Which medication you took matters.

Which GLP-1 medications are involved in the vision loss litigation?

The court has described the federal proceeding as involving GLP-1 receptor agonists and GLP-1/GIP dual receptor agonists sold under the brand names Ozempic, Wegovy, Rybelsus, Saxenda, Trulicity, Mounjaro and Zepbound. The first four are Novo Nordisk products; the last three are Eli Lilly products10.

The published research on NAION has centered on semaglutide — the active ingredient in Ozempic, Wegovy and Rybelsus13. Those two lists are not identical, and the difference is part of what the litigation is about.

What is NAION?

Non-arteritic anterior ischemic optic neuropathy — damage to the front of the optic nerve from insufficient blood flow. It usually causes sudden, painless vision loss in one eye, and is often first noticed on waking48.

Is NAION permanent?

Often, yes. There is no treatment established to reverse the damage, and vision lost to NAION frequently does not return8.

What that means for any individual is a question for the clinicians treating that person.

Does taking semaglutide mean someone will develop NAION?

No. The European Medicines Agency’s safety committee reviewed the available data and concluded that NAION is a very rare side effect of semaglutide medicines — occurring in up to 1 in 10,000 people who take them3.

Very rare is not the same as impossible, and it is not the same as likely.

Does the research prove that semaglutide caused an individual’s vision loss?

No, and the studies themselves say so. Observational research of this kind identifies associations across populations; it does not establish what caused one person’s injury12.

That is the work an individual case does — through the prescription history, the medical records and expert analysis of that one person’s circumstances.

What should I do if my vision suddenly changes?

Treat it as a medical emergency and seek prompt medical attention. Do not wait to see whether it improves, and do not wait to speak to a lawyer first.

The legal question keeps. Vision often does not.

What if I don’t remember exactly which GLP-1 medication I took?

That is common, particularly for people who were switched between medications or doses.

Start with what you remember — roughly when, who prescribed it, which pharmacy filled it. Pharmacy and prescribing records can usually reconstruct the rest.

What if I don’t have all of my medical records?

Most people don’t. If you have them, keep them. If you don’t, that should not stop you from calling — requesting records is part of the work we do.

Is there a settlement in the GLP-1 vision loss cases?

Not as of this page’s last review. The federal docket in MDL No. 3163 contains no settlement program, no claims administrator and no mediation order, and the court has set a schedule that runs through 2027 on the threshold question of whether these medications can cause NAION5.

Be careful with any website that suggests otherwise. A common benefit fund — which this MDL does have — is a mechanism for allocating the costs and fees of plaintiffs’ counsel. It is not money for claimants.

What compensation is available?

The existence and amount of any potential recovery depend on the facts, the applicable law and the outcome of the case. No result is guaranteed.

Where damages are legally recoverable, claims may involve categories of loss associated with an injury, including medical costs and the effects on work and daily life. What may be recoverable in a particular case has to be evaluated individually.

What does it cost to talk to a lawyer about this?

Nothing. Case reviews are free, and if we take the case we take it on contingency — no money up front, and no attorney’s fee unless we recover.

It also means we say no when the claim is not there, and tell you why.

Can I contact CBW Law if I’m unsure whether I have a claim?

Yes. That is most of the calls we take on this case type.

You do not need to know the science, you do not need to understand the MDL, and you do not need to decide whether your history fits a lawsuit before speaking with us. Tell us what you took, what happened to your vision and what you were told. We’ll start there.

This page is general information about how GLP-1 vision loss claims work. It is not legal advice, it does not create an attorney-client relationship, and it is not medical advice about anyone’s diagnosis or treatment. Do not start, stop or change a prescription because of anything written here — that is a conversation with the clinician who prescribed it.