Glaucoma. Illustration showing flow of aqueous humour (red arrows) in the eye in glaucoma. Aqueous humour is fluid produced by the ciliary processes surrounding the lens (round blue body, lower left). Normally this fluid passes through the pupil into the anterior chamber (light blue domed region), where it drains away via the Canal of Schlemm (blue, top centre). Glaucoma is an increase in pressure within the eye, usually resulting from a defect in the drainage of the aqueous humour. This may be due to infection, trauma or other causes. It is an important cause of blindness in the elderly. Treatment is by drugs to control the pressure, or drainage surgery.