GLAUCOMA
Glaucoma: A common eye condition in which the fluid pressure inside the eye rises to a level higher than healthy for that eye. If untreated, it may damage the optic nerve, causing the loss of vision or even blindness.
The elderly, African-Americans, and people with family histories of the disease are at greatest risk. There are no symptoms in the early stage of glaucoma. Glaucoma is often called “the sneak thief of sight.” Often, by the time the patient notices vision loss, glaucoma can only be halted, not reversed.
CAUSES
Elevated pressure in the eye is the main factor leading to glaucomatous damage to the eye (optic) nerve. Glaucoma with normal intraocular pressure is discussed below in the section on the different types of glaucoma. The optic nerve, which is located in back of the eye, is the main visual nerve for the eye. This nerve transmits the images we see back to the brain for interpretation. The eye is firm and round, like a basketball. Its tone and shape are maintained by a pressure within the eye (the intraocular pressure), which normally ranges between 8 millimeters (mm) and 22 mm of mercury. When the pressure is too low, the eye becomes softer, while an elevated pressure causes the eye to become harder. The optic nerve is the most susceptible part of the eye to high pressure because the delicate fibers in this nerve are easily damaged either by direct pressure on the nerve or decreased blood flow to the nerve.
The front of the eye is filled with a clear fluid called the aqueous humor, which provides nourishment to the structures in the front of the eye. This fluid is produced constantly by the ciliary body, which surrounds the lens of the eye. The aqueous humor then flows through the pupil and leaves the eye through tiny drainage channels called the trabecular meshwork. These channels are located at what is called the drainage angle of the eye. This angle is where the clear cornea, which covers the front of the eye, attaches to the base (root or periphery) of the iris, which is the colored part of the eye. The cornea covers the iris and the pupil, which are in front of the lens. The pupil is the small, round, black-appearing opening in the center of the iris. Light passes through the pupil, on through the lens, and to the retina at the back of the eye.
In most people, the drainage angles are wide open, but in some individuals, they can be narrow. For example, the usual angle is about 45 degrees, whereas a narrow angle is about 25 degrees or less. After exiting through the trabecular meshwork in the drainage angle, the aqueous fluid then drains into tiny blood vessels (capillaries) into the main bloodstream.
if the eye’s trabecular meshwork becomes clogged or blocked, the intraocular pressure may become elevated. if too much fluid is being produced within the eye, the intraocular pressure may become too high. In either event, since the eye is a closed system, if it cannot adequately remove the increased fluid, the pressure builds up and optic-nerve damage may result.
SIGNS AND SYMPTOMS
- Hazy or blurred vision
- The appearance of rainbow-colored circles around bright lights
- Severe eye and head pain
- Nausea or vomiting (accompanying severe eye pain)
- Sudden sight loss
- Eye redness
If left untreated, glaucoma will eventually cause blindness. Even with treatment, about 15 percent of people with glaucoma become blind in at least one eye within 20 years.
DIAGNOSIS
Early detection, through regular and complete eye exams, is the key to protecting your vision from damage caused by glaucoma. A complete eye exam includes five common tests to detect glaucoma.
Tonometry
Tonometry measures the pressure within your eye. During tonometry, eye drops are used to numb the eye. Then a doctor or technician uses a device called a tonometer to measure the inner pressure of the eye.
Ophthalmoscopy
This diagnostic procedure helps the doctor examine your optic nerve for glaucoma damage. Eye drops are used to dilate the pupil so that the doctor can see through your eye to examine the shape and color of the optic nerve.
Perimetry
Perimetry is a visual field test that produces a map of your complete field of vision. This test will help a doctor determine whether your vision has been affected by glaucoma.
Gonioscopy
This diagnostic exam helps determine whether the angle where the iris meets the cornea is open and wide or narrow and closed.
Pachymetry
Pachymetry is a simple, painless test to measure the thickness of your cornea — the clear window at the front of the eye.
TREATMENT
Glaucoma can be treated with eye drops, pills, laser surgery, traditional surgery or a combination of these methods. The goal of any treatment is to prevent loss of vision, as vision loss from glaucoma is irreversible. The good news is that glaucoma can be managed if detected early, and that with medical and/or surgical treatment, most people with glaucoma will not lose their sight.