A disturbance in the fluid balance with the eyeball and a resulting rise in eye pressure are the two main causes of glaucoma, an eye condition. If allowed to persist, glaucoma may damage vision by pressing against the optic nerve. One of the main symptoms of glaucoma is tunnel vision. Well, in other words, an increasingly restricted field of vision, even though you can still focus perfectly well.
Other warning signs and symptoms that may or may not be present are headaches and seeing auras or haloes around bright objects. Because glaucoma is an age-associated defect, it is rarely seen in people under 35, and because it can be absolutely symptomless in its early stages by the time it is diagnosed medically, the process has often gone so far that the sufferer can be classified as blind for health insurance purposes.
You should have an eye test at about the age of 45 to check that you have not got it. This is particularly important if there is a history of it in your family. Once detected, glaucoma can never be cured, but it can be controlled in one of three ways: medically through the prescription of certain drugs, surgically in order to release pressure inside the eye, or through the use of prescription eye drops that use a drug called pilocarpine to constrict the pupil, making the wearing of glasses unnecessary.
