Key points
- Most glaucoma has no early symptoms; about half of people with it don't know.
- Loss starts in side vision, and the other eye and the brain hide it.
- Age over 60, Black or Hispanic/Latino heritage over 40, and family history raise risk.
- Treating early glaucoma lowers the chance of it getting worse.
What glaucoma does
Glaucoma is a group of diseases that damage the optic nerve, the bundle of nerve fibers that carries what your eye sees to your brain.[1] The damage usually happens when fluid pressure inside the eye is too high for that nerve, although it can happen at normal pressure too.[1]
The most common type in the United States is open-angle glaucoma.[2] Fluid drains from the eye too slowly, pressure rises gradually, and nerve fibers are lost a few at a time.
Why you don't notice it
Glaucoma usually takes side vision first, often on the side closest to the nose.[2] Three things hide that loss:
- Your other eye covers for it. The two fields overlap, so a gap in one eye is filled in by the other.
- Your brain fills in the blanks. Missing areas aren't seen as black. They're simply not noticed.
- It's slow. Change over months or years doesn't stand out.
That's why about half of people with glaucoma don't know they have it.[3]
Who is at higher risk
Risk is higher if you are over 60, if you are Black or Hispanic/Latino and over 40, or if you have a family history of glaucoma.[2] Asian adults and people with diabetes are also at higher risk.[3] Other risk factors include higher eye pressure, a thin cornea and low corneal hysteresis.[4]
How it's found
A comprehensive dilated eye exam, including a test of your side vision, is the only way to know whether you have glaucoma.[2] A glaucoma evaluation adds a pressure check, a look at the drainage angle, an OCT scan of the nerve, and a visual field test.[4]
Why finding it early matters
In the Early Manifest Glaucoma Trial, people with early glaucoma whose pressure was lowered by about 25% were less likely to get worse: about 45% progressed, compared with 62% of people who weren't treated.[5] Treatment can't bring back lost vision, but it can stop or slow further loss.[2]
When to see a doctor
Ask for a comprehensive dilated eye exam if you're at higher risk, or if you've been told your pressure or optic nerve looks unusual.
Emergency: If you have sudden eye pain with redness, blurred vision, halos around lights, headache, nausea or vomiting, or sudden vision loss or a curtain over your vision, go to an emergency department now or call 911.
Sources and references
- Centers for Disease Control and Prevention. About common eye disorders and diseases. Vision and Eye Health. View source (opens in a new tab)
- National Eye Institute. Glaucoma. National Institutes of Health. View source (opens in a new tab)
- Centers for Disease Control and Prevention. Announcement: Glaucoma Awareness Month, January 2016. MMWR Morb Mortal Wkly Rep. 2016;65(1):12. View source (opens in a new tab)
- Gedde SJ, Bowden EC, Challa P, et al; American Academy of Ophthalmology Preferred Practice Pattern Glaucoma Committee. Primary Open-Angle Glaucoma Preferred Practice Pattern. Ophthalmology. 2026;133(4):P1-P103. doi:10.1016/j.ophtha.2025.12.029 View source (opens in a new tab)
- Heijl A, Leske MC, Bengtsson B, et al; Early Manifest Glaucoma Trial Group. Reduction of intraocular pressure and glaucoma progression: results from the Early Manifest Glaucoma Trial. Arch Ophthalmol. 2002;120(10):1268-1279. View source (opens in a new tab)
This article is general education for adults and is not a substitute for personal medical advice.