Glaucoma is a group of eye diseases that damage the optic nerve. It can permanently reduce vision, often before you notice a change. An eye examination can find damage early enough to start treatment that helps protect the sight you still have.
What symptoms should you watch for?
The most common form, open-angle glaucoma, usually has no early symptoms. Over time, side vision may fade gradually. You cannot rely on pain or a normal-looking eye to tell you whether you have it.
A sudden attack of angle-closure glaucoma is different. Severe eye pain, a red eye, blurred vision and nausea may appear together. This is an emergency; see the urgent-care advice below.
When should you arrange an eye examination?
Ask an eye care professional about your personal risk and how often to have a comprehensive dilated eye examination, especially if a close relative has glaucoma or you have been told your eye pressure is high. Glaucoma can also occur at eye pressures within the usual range.
How is glaucoma diagnosed?
An examination may include eye-pressure measurement, a dilated view of the optic nerve, a visual-field test to check side vision and an assessment of the drainage angle. One pressure reading alone cannot give the full picture.
What does treatment involve?
Treatment aims to prevent further damage, often by lowering eye pressure. Depending on the type and stage, an eye specialist may recommend prescription eye drops, laser treatment or surgery. Lost vision generally cannot be restored, so follow-up matters even when your sight seems unchanged.
If you are prescribed drops, use them on the schedule you were given. Ask your eye care team to show you how to put them in, and tell them if side effects or cost make it hard to continue. Do not stop treatment without discussing an alternative with them.
When is urgent help needed?
Seek emergency eye care immediately for sudden severe eye pain, particularly with a red eye, blurred vision, headache or nausea. Acute angle-closure glaucoma needs prompt treatment to protect vision.
Related topics
Sources and further reading
- National Eye Institute: Glaucoma
- National Eye Institute: Types of glaucoma
- National Eye Institute: How to put in eye drops
Last reviewed: 28 September 2026. This page provides general health information and does not replace individual medical assessment or treatment.