Glaucoma damages the eye’s optic nerve. It is a leading cause of blindness in the United States. It usually happens when the fluid pressure inside the eyes slowly rises, damaging the optic nerve. Often there are no symptoms at first, but a comprehensive eye exam can detect it. Glaucoma refers to a category of eye disorders often associated with a dangerous buildup of internal eye pressure (intraocular pressure or IOP), which can damage the eye’s optic nerve that transmits visual information to the brain.
In most people, the filtering angles are wide open, although in some individuals, they can be narrow. For example, the usual filtering angle is about 45 degrees, whereas a narrow angle is about 25 degrees or less. After exiting through the trabecular meshwork in the filtering angle, the aqueous fluid then drains into tiny blood vessels (capillaries) into the main bloodstream. The aqueous humor should not be confused with tears, which are produced by a gland just outside of the eye.
In the front of the eye is a space called the anterior chamber? A clear fluid flows continuously in and out of the chamber and nourishes nearby tissues. The fluid leaves the chamber at the open angle where the cornea and iris meet. (See diagram below.) When the fluid reaches the angle, it flows through a spongy meshwork, like a drain, and leaves the eye.
This is caused by trabecular blockage which is where the aqueous humor in the eye drains out. Because the microscopic passage ways are blocked, the pressure builds up in the eye and causes imperceptable very gradual vision loss. Peripheral vision is affected first but eventually the entire vision will be lost if not treated. Diagnosis is made by looking for cupping of the optic nerve.
Angle-closure (acute) glaucoma is caused by a shift in the position of the iris of the eye that suddenly blocks the exit of the aqueous humor fluid. This causes a quick, severe, and painful rise in the pressure within the eye (intraocular pressure). Angle-closure glaucoma is an emergency. This is very different from open-angle glaucoma, which painlessly and slowly damages vision.
Glaucoma is often referred to as the “silent thief of sight,” because most types typically cause no pain and produce no symptoms. For this reason, glaucoma often progresses undetected until the optic nerve already has been irreversibly damaged, with varying degrees of permanent vision loss.
Neovascular glaucoma results from abnormal blood vessel growth that blocks the fluid drainage channels of the eye, resulting in increased eye pressure. Low blood supply to the eye as a result of diabetes, insufficient flow of blood to the head due to blocked arteries in the neck, or blockage of blood vessels in the back of the eye can cause the abnormal blood vessel growth.
The treatment of glaucoma is aimed at reducing intraocular pressure by improving aqueous outflow, reducing the production of aqueous, or both. Doctors accomplish these treatment goals with eyedrops, systemic medications, laser treatment, surgery, or a combination of treatments. If your doctor determines that you have elevated intraocular pressure , an excavated optic disk and loss of visual field, you’ll likely be treated for glaucoma. If you have only slightly elevated eye pressure, an undamaged optic nerve and no visual field loss, you may not need treatment, but your doctor may advise more frequent examinations to detect any future changes.