Eye and vision care

What is glaucoma?

Glaucoma is a disease of the eye characterized by increased pressure inside the eye. Although this condition often has no symptoms, when detected early, it is easily treatable. Left untreated, however, it can slowly rob sight and lead to blindness.

Simply put, glaucoma is a condition in which pressure increases inside the eye. If you think of your eye as a sink filling with water and the drain closed or clogged, glaucoma is quite similar. If you place a rubber disc over the drain, as the sink continues to fill, you'll notice the rubber disc will soon begin to bulge outward. Similarly, this is what happens inside the eye. If left untreated, this can lead to impaired vision or even blindness.

Normally, the eye drains excess fluid through a network of tissues commonly known as a drainage angle. Problems arise when normal drainage through the drainage angle no longer occurs. As long as the drainage angle is obstructed or not functioning properly, intraocular pressure will continue to mount. This in turn reduces blood flow to the retina and optic nerve. Without proper nourishment in the form of blood, fibers of the optic nerve can die. A patient's vision begins to dim. If left untreated for a prolonged period, this most often leads to blindness.¹

Types of glaucoma²

There are two types of glaucoma—primary open angle glaucoma and angle closure glaucoma.

Primary open angle glaucoma (POAG)

This is the most common form of glaucoma, and it occurs when the eye's drainage angle becomes clogged over time. Pressure inside the eye mounts because the correct amount of fluid cannot drain out of the eye. In open angle glaucoma, the entrances to the drainage canals should be clear and functioning properly. The clogging problem actually occurs inside the drainage canals, much like the clogging that can occur in the pipe under a sink.

Primary open angle glaucoma often has no symptoms or early warning signs. Left undiagnosed or untreated, it can lead to a gradual loss of vision. POAG develops slowly, often without noticeable loss of vision, over the course of several years. POAG can be managed with medication, particularly if detected and treated early.

Angle closure glaucoma

Also known as acute glaucoma or narrow angle glaucoma, aAngle closure glaucoma is much more rare and differs greatly from Primary Open Angle Glaucoma in that pressure can mount very rapidly. This occurs when the drainage canals get clogged or covered over, much like placing a rubber disc over the drain in a clogged sink. In angle closure glaucoma, the angle between the iris and the cornea is not as wide as it should be, and as a result, when the pupil enlarges, the edge of the iris covers and obstructs the drainage canals.

Symptoms of glaucoma

Early symptoms of glaucoma include blurred vision, loss of peripheral vision (also known as decreased visual field), teary eyes, and headaches. In more acute and advanced cases, symptoms include sudden acute eye pain, blurred vision, the appearance of "halos" or rainbows around lights, and nausea or vomiting.

Testing for glaucoma

Early detection of glaucoma depends on regular eye examinations. Glaucoma checks consist of two main tests: tonometry and ophthalmoscopy.³

Tonometry

Tonometry is a test conducted to measure the pressure inside the eye. Drops are used to numb the eye, and the doctor will also sometimes use an orange stain. Neither is painful, and neither has any harmful effects, although the eyes may water a little following the test, and tears may have a slight orange tinge as a result of the stain. This effect is very short-lived. Using a device known as a tonometer, the doctor will measure the pressure in the eye. The tonometer presses slightly against the cornea. By measuring the eye's resistance, the doctor can determine the pressure inside the eye.

Ophthalmoscopy

Opthalmoscopy is used to examine inside the eye and to examine the optic nerve. In a darkened room, the doctor will examine a patient's eye using an ophthalmoscope, a device with a light at the end that will magnify the eye, allowing the doctor to look inside and examine the shape and color of the optic nerve. If pressure inside the eye is outside the normal range, or if the optic nerve appears unusual, the doctor may recommend additional tests for glaucoma: perimetry and/or gonioscopy.

Perimetry

Also called a visual field test, perimetry requires patients to look straight ahead and to indicate when a moving light passes through their side (or peripheral) vision. This test allows the technician (although computerized machines are more common now) to draw a map of your vision. Significant blind spots may be indicative of glaucoma.

Gonioscopy

In gonioscopy, the doctor examines the eye to determine whether the angle where the iris meets the cornea is open or closed. By doing this, he can determine whether open angle or angle closure glaucoma is present.

Treatments for glaucoma

Although glaucoma cannot be cured, there are non-invasive means to control and maintain it, and many patients live with glaucoma without experiencing any of the effects associated with progression of the disease. Eyedrops such as Xalatan®, Propine®, Cosopt®, Alphagan®, and Timoptic® are often prescribed to help manage pressure and keep it at an acceptable level. Pills such as Diamox® can also achieve this result, but many patients report that Diamox has undesirable side effects such as bitter aftertaste, stomach and digestive problems, constipation, and tingling in the hands and feet.

A number of medications such as asthma medications, cold and flu remedies, and antihistamines are not recommended for people with glaucoma because they have a tendency to aggravate the condition, causing increase in pressure. If unsure, always consult with your ophthalmologist or pharmacist.

In acute cases of glaucoma where the pressure suddenly "spikes", a more immediate and powerful medication, administered intravenously at a hospital, is required. These intravenous medications (e.g., Mannitol) are administered through an IV over the course of 45 to 60 minutes and because of their extreme diuretic effects, patients often report feeling cold and rather tired following treatment.

Although medication is successful in a large number of patients, for some, laser therapy and surgery may be necessary.

Glaucoma is commonly treated through the use of a laser. A small opening is created in the iris to relieve the pressure. Occasionally, an entirely new opening is created, successfully correcting the drainage problem.

Secondary glaucoma

Glaucoma can also be the result of injury, inflammation, tumor, or advanced cases of cataracts or diabetes. It can also be brought on by steroid use. Secondary glaucoma can be mild or severe, and treatment will depend on whether it is open angle or angle closure glaucoma.⁴

Who's at special risk?⁵

• Glaucoma is 6 to 8 times more common in Blacks than in Caucasians.
• People over 60 are 6 times more likely to develop glaucoma than those younger.
• People with a family history of glaucoma are 4 to 9 times more likely to develop the disease than those without a family history of glaucoma.
• Asians appear to be at some risk for angle closure glaucoma.
• Steroid users appear to be more at risk for open angle glaucoma and ocular hypertension.
• Those who have suffered an eye injury may develop glaucoma immediately after the injury or years later. This type of glaucoma, known as traumatic glaucoma, can result from a blow to the head or a direct injury to the eye. The most common sports-related injuries leading to traumatic glaucoma are baseball and boxing. When blunt trauma occurs, damage to the drainage system can lead to traumatic glaucoma. Glaucoma can also be the result of a penetrating injury.

Thankfully, glaucoma is treatable. In acute glaucoma, proper immediate treatment can often restore normal vision. In chronic glaucoma, early detection is key. By having your eyes examined regularly, particularly if you are over the age of 40, you increase your chances of detecting this disease early and reversing its effects.

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1. What is glaucoma? Marie Roy. © 2002 PageWise, Inc.
2. What is glaucoma? Glaucoma Research Foundation.
3. Diagnostic Tests. Glaucoma Research Foundation.
4. What is glaucoma? Glaucoma Research Foundation.
5. Who's at Special Risk? Glaucoma Research Foundation.