Glaucoma

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Risk Factors

Open-angle glaucoma can develop in anyone and it occurs most often in people over the age of 40. Many factors can increase the risk:

• African American
• Corticosteroid use on a regular, long-term basis
• Diabetes
• Family history of glaucoma
• High blood pressure (hypertension)
• High intraocular pressure in one or both eyes
• Myopia (nearsightedness)
• Other eye disorders (e.g., uveitis, exfoliation syndrome, tumor, lens dislocation)
• Over the age of 45 and not having regular eye exams
• Previous eye injury

The risk factor for congenital glaucoma is the presence of an autosomal recessive gene for the condition in both parents.

Signs and Symptoms

In most cases of glaucoma, there are no obvious symptoms and most people remain unaware of it until serious vision loss has occurred. Two types of glaucoma—acute angle-closure glaucoma and congenital glaucoma—do produce symptoms. Symptoms of acute angle-closure glaucoma include:

• Eye pain after watching television or upon leaving a dark theater
• Halos or rainbows around lights
• Headaches (primarily in the morning)
• Intense eye pain
• Nausea and vomiting brought on by pain
• Redness in the eyes
• Sudden increase in IOP
• Swollen or clouded cornea

Symptoms of congenital glaucoma include:

• Enlargement and/or clouding of the cornea
• Excessive tearing in one or both eyes
• Sensitivity to light (the infant may close one or both eyes in bright light)

Diagnosis

Diagnosis of glaucoma requires a thorough eye exam performed by an ophthalmologist or an optometrist. The four diagnostic tests for glaucoma are tonometry, ophthalmoscopy, perimetry, and gonioscopy.

Tonometry
There are three ways to perform tonometry (measure IOP). In the Schiotz method, the eye first is anesthetized with drops. The patient then lies on a table and looks at a spot on the ceiling. A tonometer is lowered onto the surface of the eye for a few seconds to measure intraocular pressure. The procedure is repeated on the other eye.

The applanation method measures how much force is required to flatten a portion of the cornea. This procedure is done with the patient sitting. The side of the eye is touched lightly with a fine strip of paper stained with an orange dye called fluorescein. This stains the front of the eye and helps with the examination. Anesthetic drops are placed in the eyes. A slit lamp microscope (instrument that utilizes a high-intensity light to examine the eyelids, sclera, lens, conjunctiva, iris, and cornea) is placed in front of the patient, who rests their chin and forehead on a support to keep their head steady. The instrument is moved forward until the tonometer touches the eye. Looking through the eyepiece, the doctor adjusts the tension on the tonometer and measures eye pressure.

In the noncontact method, the eye is not directly touched with an instrument. This test is performed while the patient is sitting with their chin resting on a padded support. The patient stares straight into the examining instrument, is asked to fixate on a target of light, and a puff of air is blown. Pressure is calculated by evaluating the change in light reflected off the cornea as the air is blown into the eye.

Ophthalmoscopy
Opthalmoscopy is used to examine the interior of the eye, including the optic nerve. Using an ophthalmoscope (small, hand-held instrument consisting of a battery-powered light and a series of lenses) the doctor can see if there has been damage to the optic nerve.

If tonometry reveals normal pressure and the optic nerve looks healthy, testing ends. However, if pressure is abnormal and/or the optic nerve appears damaged, more tests are done.

Perimetry
Perimetry is the evaluation the patient's total visual field (i.e., area where objects can be seen while the eye is looking straight ahead). It can be performed in different ways. A common method is to have the patient stare straight ahead while the doctor moves a light through the field of vision. The patient indicates when the light is seen. This helps the physician evaluate peripheral vision and determine if vision loss has occurred.

Gonioscopy
Gonioscopy is the examination of the drainage angle (i.e., trabecular meshwork, Canal of Schlemm), where the aqueous fluid normally exits the eye. The eyes are anesthetized with drops and, using a special biomicroscope, a gonioscopy lens is placed on the cornea. This lens has mirrors that allow the physician to inspect the drainage area and determine if open-angle or angle-closure glaucoma is present.

Glaucoma, Risk Factors, Signs and Symptoms, Diagnosis reprinted with permission from visionchannel.net
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