Diagnosis and Treatment of Glaucoma

Glaucoma is a serious disease of the eye which may lead to loss of peripheral vision and, if untreated, total blindness. The precise cause of glaucoma is not known, but is related to the production and removal of the fluid in the eye known as the aqueous humor. It is a transparent fluid that provides nutrition to the lens and cornea and transmits light rays to the retina at the back of the eye. Aqueous humor leaves the eye through a sieve-like tissue called the trabecular meshwork, and glaucoma is believed to be caused by changes in the meshwork that prevent aqueous humor from leaving the eye. The result is increased pressure within the eye. There may be no symptoms initially and there is no cure, although not all people with increased intraocular pressure have glaucoma.

Four criteria are used to diagnose glaucoma:

1. pressure within the eye,
2. the appearance of the meshwork,
3. the appearance of the optic nerve,
4. the individual's visual field, particularly peripheral vision.

A routine eye exam usually includes a check of the pressure inside the eye, and most ophthalmologists will examine the meshwork as well. Dilating the pupils is usually necessary to examine the meshwork and optic nerve.

Research into glaucoma causes and treatments is ongoing. There are a number of studies underway examining the genetics and heritability of glaucoma as well as new approaches to glaucoma therapy. The Glaucoma Research Foundation, for example, cites several goals including protecting and restoring the optic nerve; accurately monitoring the progression of glaucoma; finding the genes responsible for glaucomas; understanding the intraocular pressure system and developing better treatments; and determining risk factors for glaucoma damage.

Three types of treatments are available for Galucoma: 1) medication -- eye drops and pills, 2) laser procedures and 3) incisional surgery.

Medications. The four main families of medications are: beta blockers (Timoptic, Betoptic), carbonic anhydrase inhibitors (Trusopt, Azopt), alpha agonists (Alphagan, Iopidine) and prostaglandin (Xalatan). The first three types of medications decrease production of fluid in the eye, while prostaglandin helps fluid leave the eye through a different pathway located at the back of the eye.

Laser procedures. An argon laser may be used to perform a procedure called a trabeculoplasty. The laser is focused into the meshwork where it alters cells there to let aqueous fluid leave the eye more efficiently. It is a painless procedure, taking 10-20 minutes, in a doctor's office or outpatient facility. According to the Glaucoma Foundation, nearly 80% of patients respond well enough to the procedure to delay or avoid further surgery. Some patients can eventually discontinue glaucoma medication. However, pressure increases again in more than half of all patients within two years after laser surgery, according to the National Eye Institute. A laser is also sometimes used to make a small hole in the colored part of the eye (the iris) to allow the aqueous fluid to flow more freely within in the eye.

Incisional surgery. Open, incisional surgery may be performed if medication and initial laser treatments are unsuccessful in reducing pressure within the eye. One type of surgery, a trabeculectomy, creates an opening in the wall of the eye so that aqueous humor can drain. If it performed under local anesthetic as an outpatient procedure or may require a brief hospital stay. Most patients can discontinue glaucoma medication after surgery, although 10 to 15% will require additional surgery. About one-third of trabeculectomy patients develop cataracts within five years, according to the Glaucoma Foundation. If the trabeculectomy fails, another type of surgery places a drainage tube into the eye between the cornea and iris. It exits at the junction of the cornea and sclera (the white portion of the eye). The tube drains to a plate that is sewn on the surface of the eye about halfway back. A final -- and infrequently used -- surgical procedure uses a laser or freezing treatment to destroy tissue in the eye that makes aqueous humor

Surgery may save remaining vision, but it does not improve sight. Vision may actually be worse following surgery. The key to preserving vision in a glaucoma patient remains early detection. With early detection, the disease can be more easily managed without invasive procedures.

Also see Dr. Robinson's HealthLink article on Glaucoma Basics.

James C. Robinson, MD
Associate Professor of Ophthalmology
Medical College of Wisconsin
Froedtert & Medical College Eye Institute

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.