Glaucoma is a condition which can affect sight, usually due to build up of pressure within the eye.
Glaucoma often affects both eyes, usually to varying degrees. One eye may develop glaucoma quicker than the other.
The eyeball contains a fluid called aqueous humour which is constantly produced by the eye, with any excess drained though tubes.
Glaucoma develops when the fluid cannot drain properly and pressure builds up, known as the 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).
Although any vision which has been lost to glaucoma cannot be recovered, with early diagnosis, careful monitoring and regular use of treatments, the vast majority of people retain useful sight for life. The only way to know if you have glaucoma is to have your eyes checked regularly.