Glaucoma is a term that describes a group of eye conditions that affect vision. Glaucoma often affects both eyes, usually in varying degrees. One eye may develop glaucoma quicker than the other.
If left untreated, glaucoma can cause blindness. But if it is diagnosed and treated early enough, further damage to vision can be prevented
Glaucoma occurs when the drainage tubes (trabecular meshwork) within the eye become slightly blocked. This prevents eye fluid (aqueous humour) from draining properly.
When the fluid cannot drain properly, pressure builds up. This is called intraocular pressure. This can damage the optic nerve, which connects the eye to the brain, and the nerve fibres from the retina (the light-sensitive nerve tissue that lines the back of the eye).
Other sources of information
Find out more from NHS Choices.