Signs of Glaucoma: Why You Usually Can’t Feel It, and How to Catch It Early

Why glaucoma is so easy to miss

Glaucoma is a group of eye diseases that damage the optic nerve, the cable that carries images from the eye to the brain. According to the NEI, the most common type usually has no early symptoms. Vision loss starts at the edges, especially the part of your side vision closest to your nose, and creeps inward slowly.

Because it happens slowly and at the edges of your vision, you can lose a lot of side vision before anything seems wrong. By the time you notice, the damage is permanent.

Check your risk in 30 seconds

Since early glaucoma can’t be felt, knowing your risk is what tells you to get checked. This list combines the risk factors named by the NEI and the American Academy of Ophthalmology (AAO):

Even with no risk factors, the AAO recommends a baseline comprehensive eye exam at age 40, when early signs of eye disease may first appear. Your ophthalmologist then sets how often to come back.

The signs, when they appear

There are two main forms, and they behave very differently:

• Open-angle glaucoma (the most common): no warning signs in the early stages, the AAO says. Over time, side vision slowly narrows.
• Angle-closure glaucoma: can come on suddenly as an attack, with pain and blurry vision. That’s an emergency (see below).

Glaucoma can also make it harder to see at night. See our guide to glare and night vision problems for the other common causes.

The emergency form: an angle-closure attack

The AAO calls an acute angle-closure attack a true eye emergency. Call an ophthalmologist right away, or go to the emergency room, if you suddenly have:

• Blurry vision
• Severe eye pain
• A headache
• Nausea or vomiting
• Rainbow-colored rings or halos around lights

The NEI also lists a red eye among the warning signs. Don’t wait to see whether it passes.

Why “normal eye pressure” isn’t the all-clear

Many people think glaucoma simply means high eye pressure. It’s a major risk factor, but the NEI notes that some people with high eye pressure never get glaucoma, and one type of glaucoma happens in people with normal eye pressure.

That’s why a quick pressure check on its own isn’t a full glaucoma test.

The exam that finds it

Eye doctors check for glaucoma as part of a comprehensive dilated eye exam. The NEI describes it as simple and painless:

• Dilating drops widen your pupils so the doctor can look at the optic nerve.
• A visual field test checks your side vision, where glaucoma starts.
• Eye pressure may be measured too, as one piece of the picture.

When you book, say that you want to be checked for glaucoma, and mention any risk factors from the list above.

What treatment can do

The NEI lists three main treatments:

• Prescription eye drops, the most common treatment, which lower eye pressure
• Laser treatment to help fluid drain from the eye
• Surgery, if other treatments don’t work

Treatment can’t restore lost vision, but it can stop glaucoma from getting worse. That’s why finding it early matters so much, and why it’s important to keep using drops exactly as prescribed, even when your eyes feel fine.

Can supplements help glaucoma?

Not in any proven way. The AREDS2 formula sold for eye health was tested for macular degeneration, not glaucoma, and our AREDS2 evidence guide explains why it isn’t a glaucoma treatment.

The one supplement being seriously studied is nicotinamide (a form of vitamin B3). Small, short trials in people already on glaucoma treatment found some early improvements in how the retina worked, at doses of 1 to 3 grams a day, far more than any multivitamin. But a systematic review published in September 2026 concluded that the evidence isn’t enough to recommend it routinely, and larger, longer trials are still needed.

So: don’t take high-dose vitamin B3 on your own, and never use any supplement in place of your prescribed drops. If you’re curious, ask your eye doctor whether a trial is recruiting near you.