Conditions and symptoms
What Is NAION? Why Some Labels Warn About Vision Loss
NAION · say it: NAY-onAlso written: non-arteritic anterior ischemic optic neuropathy, ischemic optic neuropathy, eye stroke
Short answer
NAION is sudden loss of vision in one eye caused by reduced blood flow to the optic nerve. Sudden vision loss needs urgent medical help.
What it means
NAION stands for non-arteritic anterior ischemic optic neuropathy. It happens when blood flow to the front of the optic nerve, which carries signals from the eye to the brain, is reduced. It usually causes sudden, painless loss or blurring of vision in one eye, often noticed on waking. Any sudden loss of vision needs urgent medical help, the same day.
It appears on the labels of erectile dysfunction medicines (PDE5 inhibitors such as sildenafil and tadalafil), which advise stopping the medicine and seeking medical care straight away if sudden vision loss occurs. It is also mentioned for some GLP-1 medicines in some regions. Risk factors include a small, crowded optic disc, diabetes, high blood pressure, smoking and being over 50; people who have had NAION before may be advised to avoid these medicines.
'Non-arteritic' separates it from arteritic optic neuropathy, which is caused by giant cell arteritis, an inflammation of arteries that needs different urgent treatment.
Where you may see it
- 'Warnings' sections of sildenafil, tadalafil and vardenafil labels
- Medicine leaflets under 'Sudden loss of vision'
- Ophthalmology letters
📄 How it looks on a report
Advise patients to stop use and seek medical attention in the event of a sudden loss of vision in one or both eyes, which could be a sign of NAION.
🙅 What it does not mean
- A label warning does not mean it is likely to happen.
- Blurred vision that clears quickly is not usually NAION, but sudden loss should always be checked.
- It is not the same as a stroke in the brain, although both involve reduced blood flow.
🗒️ Questions to ask your doctor
💊 Medicines whose labels mention “NAION”
Plain-English explanations of each medicine, from its official FDA label.
- Sildenafil
A phosphodiesterase-5 (PDE5) inhibitor, a medicine used to treat erectile dysfunction
- Tadalafil
a phosphodiesterase 5 (PDE5) inhibitor, which is a medicine that blocks an enzyme called PDE5
🔗 Read more from trusted sources
- “NAION” on MedlinePlus ↗
US National Library of Medicine
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