In an eye with open-angle glaucoma, the aqueous humor drains too slowly through the channel system, creating a chronic rise in fluid pressure inside the eye. This elevated pressure may gradually interrupt the metabolic processes of cells in the optic nerve, leading to a progressive destruction of nerve fibers that are essential for vision.
The loss of sight is gradual. It begins as loss of side vision, then it continues toward the center of vision, until finally all sight is destroyed. Because the visual loss is gradual in the early stages of the disease, few signs of the disorder are recognized.