This is a group of conditions in which intraocular pressure rises due to impaired drainage of aqueous fluid through the scleral venous sinus(canal of Schlemm) in the angle between the iris and cornea in the anterior chamber. Persistently raised intraocular pressure may damage the optic nerve by:
- Mechanical compression.
- Compression of its blood supply causing ischaemia.
Damage to the optic nerve impairs vision,and the extent varies from some visual impairment to complete loss of sight.
PRIMARY GLAUCOMAS.
Primary open-angle glaucoma. There is a gradual painless rise in intraocular pressure with progressive loss of vision. Peripheral vision is lost first but may not be noticed until only central vision remains. As the condition progresses,atrophy of the optic disc occurs leading to irreversible loss of vision.
Acute closed-angle glaucoma. During life the lens gradually increases in size,pushing the iris forward. In dim light when the pupil dilates,the lax iris bulges still further forward,and may come into contact with the cornea,blocking the scleral venous sinus suddenly raising the intraocular pressure.
Chronic closed-angle glaucoma. The intraocular pressure rises gradually without symptoms. Later,peripheral vision deteriorates followed by atrophy of the optic disc and loss of sight.
