Glaucoma Surgery - Symptoms and Treatment

Glaucoma is a group of disorders characterized by high intraocular pressure (lOP) that damages the optic nerve. Glaucoma may occur as a primary or congenital disease or secondary to other causes, such as injury, infection, surgery, or prolonged topical corticosteroid use.

Primary glaucoma has two forms: open-angle (also known as chronic, simple, or wide-angle glaucoma) and angle-closure (also known as acute or narrow­angle) glaucoma. Angle-closure glaucoma attacks suddenly and may cause permanent vision loss in 48 to 72 hours.

Glaucoma - one of the leading causes of blindness - affects about 2% of Americans over age 40 and accounts for about 12% of newly diagnosed blindness in the United States. The incidence is highest among males and African-American and Asian populations. In the United States, early detection and effective treatment contribute to the good prognosis for preserving vision.

Causes

Open-angle glaucoma results from degenerative changes in the trabecular meshwork. These changes block the flow of aqueous humor from the eye, which causes lOP to increase. The result is optic nerve damage. Open-angle glaucoma affects about 90% of all patients who have glaucoma and commonly occurs in families.

Angle-closure glaucoma results from obstruction to the outflow of aqueous humor caused by an anatomically narrow angle between the iris and the cornea. This causes lOP to increase suddenly. Angle-closure glaucoma attacks may be triggered by trauma, pupillary dilation, stress, or any ocular change that pushes the iris forward (for example, a hemorrhage or swollen lens).

Secondary glaucoma can proceed from such conditions as uveitis, trauma, drug use (such as corticosteroids), venous occlusion, or diabetes. In some instances, new blood vessels (neovascularization) form, blocking the passage of aqueous humor.

Symptoms

Open-angle glaucoma produces no symptoms at first because the build-up of pressure is so gradual. As the condition progresses, however, the patient will experience a smaller field of peripheral (side) vision, headaches, and visual disturbances, such as halos around lights. Eventually, the patient may not be able to see anything to either side (tunnel vision). Open-angle glaucoma can progress to blindness. 

Closed-angle glaucoma causes sudden attacks of increased pressure, resulting in blurred vision, swelling, severe pain, sensitivity to light, nausea, and halos around lights. These types of attacks need to be treated immediately. Congenital glaucoma is present at birth, with symptoms including bulging eyes, cloudy corneas, excessive tearing, and sensitivity to light.

Diagnostic tests

In addition to a complete medical history and eye examination, your eye care professional may perform the following tests to diagnose glaucoma:

• tonometry - a standard test to determine the fluid pressure inside the eye.
• pupil dilation - the pupil is widened with eye drops to allow a close-up examination of the eye's retina.
• visual acuity test - the common eye chart test (see above), which measures vision ability at various distances.
• visual field - a test to measure a person's side (peripheral) vision. Lost peripheral vision may be an indication of glaucoma.

Treatment

Most patients with glaucoma require only medication to control the eye pressure. Sometimes, several medications that complement each other are necessary to reduce the pressure adequately. These include beta-adrenergic blockers, such as timolol (used cautiously in asthmatics or patients with bradycardia) or betaxolol. Other drug treatments include epinephrine to dilate the pupil (contraindicated in angle­closure glaucoma) and miotic eyedrops, such as pilocarpine, to promote aqueous humor outflow.

Patients who don't respond to drug therapy may benefit from argon laser trabeculoplasty or from a surgical filtering procedure called trabeculectomy. This procedure involves creating an opening for out flowing aqueous humor.

To perform argon laser trabeculoplasty, the ophthalmologist focuses an argon laser beam on the trabecular meshwork of an open angle. This produces a thermal burn that changes the meshwork surface and facilitates the outflow of aqueous humor.

To perform a trabeculectomy, the surgeon dissects a flap of sclera to expose the trabecular meshwork. The surgeon removes a small tissue block and performs a peripheral iridectomy, which produces an opening for aqueous outflow under the conjunctiva and creates a filtering bleb. Postoperatively, subconjunctival injections of fluorouracil may be given to maintain the fistula's patency.

An iridectomy is used to relieve pressure by excising part of the iris to reestablish the outflow of aqueous humor. A few days later, the surgeon performs a prophylactic iridectomy on the other eye. This prevents an episode of acute glaucoma in the normal eye.

If the patient has severe pain, treatment may include narcotic analgesics. After peripheral iridectomy, treatment includes cycloplegic eyedrops to relax the ciliary muscle and to decrease inflammation and there­by prevent adhesions. The end stage of glaucoma may require a tube shunt or valve to keep lOP down.

Prevention

Glaucoma cannot be prevented. Early detection can prevent vision loss and control the disease. Regular eye examinations are recommended, especially for people over the age of 35. After age 40, eye exams should be done every 2 to 4 years, and after age 60, every 1 to 2 years. Glaucoma testing is recommended every 1 to 2 years after the age of 35 for those at high risk.

Eating vitamin-rich fruits and vegetables, taking a vitamin supplement, protecting eyes from injury, and getting medical treatment for systemic illnesses promote good eye health.

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