You continuously make a fluid inside your eyes, so they have the nutrients they need to work normally. This fluid drains away naturally through tiny drainage channels (called the trabecular meshwork in an area described as the anterior chamber angle) in the front of your eyes. You can see where the angle is in the diagram below.
Your optometrist has found that your drainage channel is narrower than usual. This does not normally need any treatment. Many people have narrow drainage channels, and this doesn’t cause any problems for most people. But you may be at a greater risk of developing an eye condition called glaucoma.
Glaucoma is where the optic nerve, which connects the eye to the brain, becomes damaged. It’s usually caused by fluid building up and increasing the pressure inside the eye. Glaucoma can lead to loss of vision if it’s not diagnosed and treated early. There are two main types of glaucoma – chronic and angle closure.
Chronic glaucoma develops slowly and does not usually cause any symptoms. It affects the edges of your vision (peripheral vision) first. Many people do not realise they have chronic glaucoma, and it’s often only picked up during an eye examination. Most people with chronic glaucoma have normal drainage channels.
Angle closure glaucoma (ACG) is where the pressure inside your eye increases due to blockage or damage to the drainage channels. The increased pressure can come and go, and some people get short bursts of pain and blurred vision, particularly in low light. Sometimes the pressure increases, remains high and these symptoms do not go away – this is known as acute angle closure (AAC). Some people may also experience nausea and vomiting if these symptoms continue. Both ACG and AAC are more common in people with narrow drainage channels.
Contact your optometrist immediately if you notice the following symptoms that do not go away:
If your optometrist is not available to give you advice, you should go to your nearest eye casualty unit or A&E as soon as possible. These symptoms may be related to the narrow drainage channels, so refer to this page. They may recommend immediate treatment. If you need treatment, the eye specialist can reduce the pressure and get rid of the pain.
If you have these symptoms and they appear to go away, your vision may be still be damaged. You should see your optometrist as soon as possible and tell them you have had these symptoms.
Last updated: February 2026
