GLAUCOMA as a disease is highly misunderstood by the public. You can have perfect vision and still suffer from the potential blinding condition, with no symptoms. Glaucoma as a disease, exists in two different forms; Open Angle Glaucoma and Closed Angle Glaucoma. The Glaucomas are blinding conditions occurring when the delicate nerves within the retina that we use to see are damaged from the pressure in the eye. Generally, the first nerves to be affected are the nerves responsible for our side vision. Side vision is also known as Peripheral Vision.
It is easiest to understand Glaucoma comparing the eye to the faucet and drain mechanism of a kitchen sink enclosed in a balloon. The walls of the eye are analogous to the balloon. To keep a balloon inflated, air is blown into it. The air exerts an outward pressure on the walls of the balloon enabling the balloon to keep its shape. The eye is kept “inflated” by a watery liquid called Aqueous humor. There is a gland inside the eye that secretes aqueous into the eye, the Ciliary Body. This gland is the “faucet” of our kitchen sink. There is also a drain, the trabecular meshwork where the aqueous fluid leaves the eye. In the healthy eye, Aqueous is secreted, circulated and drained through the trabeculum with pressure maintained between 8 mmHg (millimeters of mercury) to 22-23 mmHg.
Open Angle Glaucoma
In an eye with Open Angle Glaucoma, the pressure is too high either because too much aqueous fluid is entering the eye, or not enough aqueous fluid is able to drain away, or both. Occasionally the person has nerve fibers that are dying without any apparent pressure problems. This is termed Ocular Hypertension or Low Tension Glaucoma. The cause of Ocular Hypertension is unknown. Open Angle Glaucoma is painless and slowly blinding from the peripheral vision inward. Untreated, total vision loss can occur slowly over years without the patient’s knowledge. The doctor is usually the first to discover changes that indicate open-angle glaucoma.
In a general eye examination, the doctor tests pressure with an air puff or blue light device. Both devices are known as tonometers. Most of the time, pressure is not enough to confirm a diagnosis of Open-Angle Glaucoma. The doctor will look inside the eye at the Optic Nerve. If the nerve looks suspicious or damaged, the doctor will run another test known as a Visual Field Test. The Visual Field test is like a video game. The patient is asked to stare straight ahead and identify flashes of light of varying intensities in their side vision by pressing a button. The doctor may ascertain a status of Glaucoma Suspect and ask the patient to return in three months, six months to monitor the pressure, the nerve appearance and the patients visual fields.
If the results are exceedingly suspicious, treatment is begun and the patient is seen every three months. Treatment usually consists of several month’s trials of different combinations of eye drops and may include a laser procedure known as A.L.T. (argon-laser trabeculoplasty) When the pressure is unable to be controlled via drops or laser surgery, a drainage shunt may be created surgically. This procedure is usually a last resort. When the final treatment plan is adopted, the patient is monitored very closely over time for any changes. People who are being treated with topical corticosteroid therapy can have increased eye pressure and temporary glaucoma secondary to their medications. Pressure usually returns to normal after removal of the steroid regimen.
Closed-Angle Glaucoma is an eye emergency and must be dealt with immediately. Closed Angle Glaucoma is usually acute and painful. It can be caused by trauma, systemic disease or can be idiopathic in nature. It can cause dimming of vision, halos around lights, nausea and headaches above the affected eye. Closed Angle Glaucoma occurs when the outflow of aqueous is completely blocked by the Iris, or colored part of the eye.
The Iris can block the angle in one of two ways. It can become lodged in the drainage angle or it can fuse to the surface of the lens of the eye, keeping aqueous from entering the anterior part of the eye where the drainage channels are located. Closed Angle Glaucoma is treated with systemic diuretic medications, a surgical procedure called iridotomy or iridectomy, surgical formation of a drainage shunt or all of the above. The condition is very rare and causes a rapid loss of vision if not treated immediately. Glaucoma is common in the general population. There is literature available and community resources such as support groups and the Lighthouse for the Blind.