Pathophysiology Intraocular pressure is determined by the rate of aqueous production in the ciliary body and the resistance to outflow of aqueous from the eye. Normal variations do not usually exceed 2 to 3 mm Hg. Intraocular pressure and blood pressure are independent of each other. Approximately 90 percent of primary glaucoma cases occur in clients with open angles. It is a multifactional disorder that is often genetically determined, bilateral, insidious in onset, and slow to progress.
Symptoms appear late when vision is impaired by damage to the optic nerve.
The most common cause of chronic open-angle glaucoma is degenerative change in the trabecular meshwork. An acute attack of angle-closure glaucoma can develop only in an eye in which the anterior chamber angle is anatomically narrow. The attack occurs due to a sudden blockage of the anterior angle by the base of the iris. When the aqueous flow is obstructed, intraocular pressure becomes markedly elevanted, causing severe pain and blurred vision or vision loss. These changes, however, develop in the presence of statistically normal intraocular pressures.