Eye Pressure and Chronic Glaucoma
The eyes are inflated by a fluid which is constantly produced inside the eye and filtered out of the eye and then back into the circulation. For various reasons the drainage mechanism of an eye may become partly blocked so the pressure in the eye rises.
OCULAR HYPERTENSION is a term used to describe eyes that generally run an elevated pressure but otherwise appear normal. About one person in every fifteen may have an eye pressure measurement over 21 mm Hg.
GLAUCOMA is the term used to imply that pressure related damage is occurring. The higher the pressure, the more likely it is that the optic nerve fibers leaving the eye to the brain will be damaged and characteristic loss of peripheral vision will occur. In the beginning there are no symptoms. The condition is normally painless, yet can cause a significant loss of vision if not detected and arrested. Glaucoma can only be detected by measuring the eye pressure, examining the optic nerve head, and carefully testing the visual sensitivity over the entire field of vision.
There are several types of glaucoma depending on the mechanism elevating the pressure.
CHRONIC OPEN ANGLE GLAUCOMA is by far the most common type of glaucoma. Roughly one fifth of eyes with elevated pressure have glaucoma, meaning that optic nerve fibers are dying. The goal of treatment is to lower the eye pressure to the point where no further loss of visual sensitivity occurs. This is done by eye drops. Laser treatment or surgery are added if no combination of drops is sufficient.
NARROW ANGLE GLAUCOMA occurs in small farsighted eyes, especially with swollen cataracts. Fluid produced behind the iris can bulge it forward causing the peripheral iris to block the outflow channels. The result can be a painful glaucoma attack. Fortunately a simple laser procedure to make a tiny hole in the peripheral iris can prevent this form of glaucoma if a narrow angle is detected during a complete eye examination.
GLAUCOMA SUSPECTS have risk factors for glaucoma but no detectable loss of vision. Some judgment is involved in deciding whom to treat and how low a pressure to aim for to prevent future loss of visual field. Some optic nerves tolerate pressure far more readily than others. Certain risk factors such as a family history, a suspicious looking nerve, diabetes, smoking or vascular disease favor treatment.
Glaucoma is controlled when the appearance of the nerve and the field of vision remain stable. When stable, a glaucoma patient is normally checked about every 3 to 6 months. More frequent pressure checks are indicated when treatment is initiated or changed. In the majority of cases early detection and a simple regimen of eye drops can prevent any serious visual loss.