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Glaucoma

• Definition of Glaucoma
• Description of Glaucoma
• Causes and Risk Factors of Glaucoma
• Symptoms of Glaucoma
• Diagnosis of Glaucoma
• Treatment of Glaucoma
• What Questions To Ask Your Doctor About Glaucoma
• Prevention of Glaucoma

Definition of Glaucoma

Glaucoma is a group of eye diseases that damage the optic nerve. The optic nerve is the main nerve to the eye (located in the back of the eye) that is responsible for transmitting electrical impulses to the brain. Damage usually occurs as a result of elevated pressure of the fluid (aqueous humor) in the eye. This damage results in gradual visual changes and then loss of vision.

Description of Glaucoma

The eye is protected by the sclera (the white covering of the eye). At the front of the eye is a clear window (the cornea) that lets light in. The iris is the colored part of the eye that controls the amount of light that can enter the eye by automatically opening and closing the pupil (the opening of the eye).

The lens (the portion of the eye lying behind the pupil) focuses light onto the retina (the innermost layer of the eye and the sensitive organ upon where light rays are focused). Nerve fibers and blood vessels in the retina gather together to form the optic nerve which carries images to the brain. The place where the optic nerve leaves the eye is called the optic disc.

The front part of the eye is filled with aqueous humor that nourishes the lens, iris and cornea, as well as maintains the shape of the eye. This fluid is continuously produced every hour by ciliary tissues.

The fluid circulates from behind the iris through the opening at the center of the pupil and into the spaces between the iris and cornea. Since this fluid is constantly produced, it must be drained. The fluid drains through an area called the drainage angle (located where the iris and cornea meet) to the trabecular meshwork (the valve that regulates pressure within the eye) to a channel (called the canal of Schlemm), and then to a system of small veins outside of the eye, called the drainage canals.

When there is a problem in the drainage, the fluid builds up in the eye and presses against the optic nerve (called intraocular pressure or IOP), resulting in glaucoma.

This increased fluid pressure actually pushes the optic nerve back into a "cupped" or concave shape. If the intraocular pressure remains too high for too long, the extra pressure damages parts of the optic nerve.

This damage appears as gradual visual changes and then loss of vision. The early visual changes are very slight and do not affect the central vision the center portion of what is seen when looking straight ahead or when reading. Certain parts of the peripheral vision (the top, sides and bottom) are affected first. Glaucoma usually occurs in both eyes, but extra fluid pressure first begins to build up in one eye.

There are many types of glaucoma, but the two most common types are open-angle glaucoma and closed angle (angle-closure) glaucoma.

Open-angle glaucoma, (also called primary open-angle glaucoma and chronic glaucoma) accounts for 90 percent of all glaucoma cases and occurs when the trabecular meshwork becomes blocked and the fluid can't get to the normal drainage canals. This blockage results in fluid build-up and intraocular pressure. The fluid build-up happens gradually.

Closed angle glaucoma, (also called acute glaucoma or angle closure glaucoma), accounts for about 9 percent of all glaucoma cases and occurs when the opening between the cornea and iris narrows, such that the fluid cannot get to the trabecular meshwork and normal drainage channels. This narrowing results in fluid build-up and intraocular pressure. The fluid build-up happens very quickly.

Other less common glaucomas include:

• normal tension glaucoma: optic nerve is damaged even though intraocular pressure is consistently within a normal range
• congenital glaucoma: incorrect or incomplete development of the eye's drainage canals during the prenatal period
• childhood glaucoma: open-angle glaucoma in infancy, childhood or adolescence
• secondary glaucoma: occurs as a result of eye injury, inflammation or tumor, or in advanced cases of cataracts or diabetes

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Causes and Risk Factors of Glaucoma

Several factors that can put a person "at risk" for developing glaucoma:

• Family history of glaucoma - There is a 20 percent chance of developing glaucoma of a parent had it, and 50 percent chance if a sibling has it.
• Age - If the person is 65 to 79 years of age, there is a 3 percent chance of developing glaucoma. If the person is 80 years of age or older, there is a 14 percent of developing glaucoma.
• Medical conditions, such as morning headaches, diabetes, lupus, Crohn's disease, rheumatoid arthritis, myopia (nearsightedness), and high blood pressure
• Use of topical steroid (prednisone or cortisone) medications
• Race - Blacks are three to four times more likely than Caucasians to develop glaucoma. Asians and Eskimos are more likely to develop glaucoma than Caucasians.
• Abnormally high intraocular pressure
• Previous eye injuries
• Recurrent blurry vision
• Pain around the eyes after watching TV or leaving a dark theater
• Seeing a rainbow - hued halos around lights at night
• Peripheral (side) vision is decreasing

Symptoms of Glaucoma

Known as the "sneak thief" of sight, open-angle glaucoma has no early warning signs or symptoms. However, as the disease progresses a person may experience:

• Tiny blind spots appear at the edges of the visual field (peripheral or side vision) that slowly get larger and spread
• Blurred vision
• Appearance of colored halos around lights
• Adjustment problems on entering a dark room
• Repeated difficulties that new eyeglass prescriptions do not help
• Peripheral (side) vision is decreasing

The symptoms of closed angle glaucoma are:

• Severely blurred vision
• Severe eye and head pain
• Nausea or vomiting
• Appearance of rainbow-colored halos around bright lights
• Rapid loss of vision

Diagnosis of Glaucoma

There are four (4) important factors in the diagnosis of glaucoma: intraocular pressure, the condition of the optic nerve, the patient's visual field and the angle where the iris meets the cornea. To detect these factors, the ophthalmologist will do the following diagnostic tests:

• Tonometry - used to measure intraocular pressure. Drops are put in the eyes to numb the eye and then the doctor measures the eye pressure, using an instrument called a tonometer. This instrument measures the inner pressure of the eye by determining how much pressure is necessary to cause a slight indentation on the outer part of the eye.
• Ophthalmoscopy - used to examine the inside of the eye, the optic nerve and the patient's field of vision. Drops are put in the eyes to dilate the pupil and then the doctor uses an instrument called an ophthalmoscope that lights up and magnifies the inside of the eye.

If the intraocular pressures are not within normal range or if the optic nerve looks unusual, the doctor may do a perimetry or a gonioscopy:

• Perimetry - a special test that produces a map of the complete field of vision.
• Gonioscopy - a test to check whether the angle where the iris meets the cornea is open or closed.

Treatment of Glaucoma

There is no cure for glaucoma, but it can be controlled. Ophthalmologists use medication and surgery to prevent further vision loss. These treatment methods are used to bring the intraocular pressure under control.

Medication

Nearly all glaucoma can be treated successfully with topical medications (applied directly to the eyes, such as eye drops or eye ointments) or oral medications (taken by mouth). There are six medications available to treat glaucoma:

1. Miotics are eye drops that help open the drainage canals and increase the flow of aqueous humor out of the eye. This type of medication includes pilocarpine (Isopto Carpine, Pilocar, Pilopine), carbachol and echothiophate.
2. Epinephrine compounds are eye drops that lower the intraocular pressure by increasing the rate of aqueous humor flow out of the eye. This type of medication includes dipivefrin (Propine) and Epifrin.
3. Beta-blockers (available as eye drops or pills) help decrease the rate at which the aqueous humor flows into the eye. This type of medication includes topical timolol (Timoptic), levobunolol (Betagan), betaxolol (Betaoptic-S), Iopidine and Ocupress. Additionally, this type of medication can also be taken orally. Oral medications include propranolol, timolol, atenolol and nadolol.
4. Carbonic anhydrase inhibitors (available as pills or eye drops) help reduce aqueous humor flow into the eye. This type of medication includes oral acetazolamide (Diamox), methazolamide (Neptazane) and chlorpropamide (Daranide), as well as topical dorzolamide (Trusopt).
5. Alpha adrenergic agonists are topical medications used to reduce the aqueous humor production and increase aqueous humor outflow. This type of medication includes apraclonidine (Iopidine) and brimonidine (Alphagan).
6. Prostaglandin analogues are topical medications that help lower intraocular pressure by increasing uveoscleral outflow (outflow through the soft tissues of the front of the eye [iris and ciliary body]). This type of medication includes latanoprost (Xalatan).

Three medications approved in 2001 are prostaglandin-related drugs (Travatan, Lumigan) and a selective alpha2 agonist called Alphagan. A study by the maker of Travatan indicated the possibility that it may work best for African-Americans with glaucoma. The drug Copaxone, normally used to treat multiple sclerosis, is being researched as a possible vaccine to protect the optic nerve from the effects of glutamate in people with glaucoma.

What Questions To Ask Your Doctor About Glaucoma

tellHow can you tell if I have glaucoma?

Will you explain how each test is performed and what it will tell?

What type of glaucoma is it and how severe is it?

Will you be prescribing a medication to treat the glaucoma?

What are the side effects?

What does the medication do to relieve the glaucoma or to stop further deterioration?

Will surgery be performed to relieve the glaucoma?

If so will you recommend laser treatment or microsurgery? What are the risks?

Will any of the symptoms go away after treatment?

Can certain medications cause glaucoma or make the condition worse?

Are there any signs or symptoms that require immediate medical attention?

Prevention of Glaucoma

While glaucoma cannot be prevented, the earlier it is diagnosed the better. Recommendations for early detection include:

--Have a test every two to four years if you are between the ages of 40 and 65.

--Have a test every one to two years if you:

• Are 65 years of age or older
• Have a family history of glaucoma
• Are of Black or Asian ancestry
• Have diabetes or a chronic inflammatory disease
• Have had previous serious eye injury
• Are taking steroids