Glaucoma. Conceptual computer artwork of the eye disease glaucoma. Glaucoma is an increased pressure in the eyeball due to an excessive amount of aqueous humour (the fluid that fills the eyeball). The eye may be producing too much aqueous humour or it may not be draining away. The increased pressure compresses the optic nerve and blood vessels in the eye, impairing vision. Treatment is with eye drops and in some cases surgery. If left untreated glaucoma can cause total blindness.