Glaucoma is a leading cause of blindness in the world. There are over 50 different types of glaucoma, each characterized by widely diverse clinical manifestations. With the exception of acute angle closure glaucoma, most glaucomas have no symptoms to alert the patient of his disease. The most common glaucoma is caused by the build up of intraocular fluid within the eye exerting an abnormally high pressure on the optic nerve. If left unchecked, this high pressure will result in nerve damage and subsequent irreversible blindness. Blindness can be prevented though. Through early detection and proper treatment, a person with glaucoma can lead a normal life with perfectly good vision.
A person diagnosed as having glaucoma once damage to the optic nerve is evident. This can be determined by examination of the optic nerve with funduscopy as well as documentation of visual damage through visual field examination. Damage to the optic nerve is due to an increase of intraocular pressure (IOP) which cuts off the flow of oxygen to the small extraocular vessels that supply the optic nerve fibers in the region of the lamina cribrosa. Intraocular pressure is directly related to the production and escape of the aqueous humor in the eye. Aqueous humor is a protein-free fluid that is produced in the ciliary processes and provides nourishment to the tissues of the eye. It flows from the posterior chamber into the anterior chamber following a pathway through the trabecular meshwork and Schlemm’s canal, finally draining from the eye through the episcleral veins into the bloodstream.
The eye must maintain a state of “dynamic equilibrium” in which the rate of entry of fluid equals the rate of escape. Intraocular pressure reflects a balance between aqueous production and aqueous outflow and any alterations of this balance will cause the intraocular pressure to rise. Overproduction of aqueous in the presence of normal outflow very rarely causes increased IOP. The interference with the mechanism of aqueous outflow is the significant factor in the etiology of the glaucomas.
- Glaucoma is a leading cause of blindness. It is an optic nerve disease, often characterized by elevated intraocular pressure, slow profession, and few, if any, symptoms.
- In glaucoma, the optic nerve loses tissue at its tip due to mechanical and vascular damage, and it appears more scooped or “cupped out”. The missing nerve fibers are responsible for the loss of visual field.
- Aqueous fluid inflow and outflow must remain matched for the intraocular pressure (IOP) to be stable and normal. If the outflow is impaired, the pressure rises. Damage to the optic nerve occurs at a different threshold pressure for each person.