Glaucoma is irreversible but preventable.

Glaucoma Diagnosis & Treatment for Houston & Galveston from The Eye Clinic of Texas

What is glaucoma?

Severe Peripheral Loss from Glaucoma

Glaucoma is a sight stealing eye disease affecting more and more of our population in Houston as we age. Glaucoma is a disease of the optic nerve, which transmits the images you see from the eye to the brain. The optic nerve is made up of many nerve fibers (like an electric cable with its numerous wires). Glaucoma damages nerve fibers, which can cause subtle loss of peripheral vision and blind spots. If not treated, it can lead to progressive loss of central vision and blindness. It’s irreversible but preventable. Glaucoma is usually, but not always, associated with elevated intraocular eye pressure. The high pressure presses on the optic nerve and damages it.

What causes glaucoma?

Glaucoma has to do with the pressure inside the eye, known as intraocular pressure (IOP). When the aqueous humor (a clear liquid that normally flows in and out of the eye) cannot drain properly, pressure builds up in the eye. The resulting increase in IOP can damage the delicate optic nerve fibers and lead to vision loss.

What are the different types of glaucoma?

Primary open angle glaucoma:

The most common form of glaucoma is primary open-angle glaucoma, in which the aqueous fluid is blocked from flowing back out of the eye at a normal rate through a tiny drainage system. Most people who develop primary open-angle glaucoma notice no symptoms until their vision is impaired.

Ocular hypertension

Ocular hypertension is often a forerunner to actual open-angle glaucoma. When ocular pressure is above normal, the risk of developing glaucoma increases. Several risk factors will affect whether you will develop glaucoma, including the level of IOP, family history, and corneal thickness. If your risk is high, your ophthalmologist may recommend treatment to lower your IOP to prevent future damage.

Angle-closure glaucoma

In angle-closure glaucoma, the iris (the colored part of the eye) may drop over and completely close off the drainage angle, abruptly blocking the flow of aqueous fluid and leading to increased IOP or optic nerve damage. In acute angle-closure glaucoma there is a sudden increase in IOP due to the buildup of aqueous fluid. This condition is considered an emergency because optic nerve damage and vision loss can occur within hours of the problem. Symptoms can include nausea, vomiting, seeing halos around lights, and eye pain.

Normal-tension glaucoma

Even some people with “normal” IOP can experience vision loss from glaucoma. This condition is called normal-tension glaucoma. In this type of glaucoma, the optic nerve is damaged even though the IOP is considered normal. Normal-tension glaucoma is not well understood, but lowering IOP has been shown to slow progression of this form of glaucoma.

Pigmentary glaucoma

This is a secondary glaucoma that’s more common in young patients. For reasons not yet understood, pigments detach from the iris, block the trabecular meshwork and prevent proper aqueous fluid outflow. This leads to elevated IOP and consequently damages the optic nerve fibers.

Exfoliation or pseudoexfoliation glaucoma

This can occur with open or closed angle glaucoma. There are flaky materials deposit in front of the lens and in the angles of the eye. The accumulation of these flakes blocks the drainage system of the trabecular meshwork and consequently leads to elevated IOP.

What are the risk factors?

• Age over 45
• Family history of glaucoma
• Black or Asian or American Indian or Hispanic ancestry
• Elevated IOP
• Diabetes
• Nearsightedness or farsightedness
• History of injury to the eye, use of steroids (in the eyes or systemically)

Childhood glaucoma

Childhood glaucoma, which starts in infancy, childhood, or adolescence, is rare. Like primary open-angle glaucoma, there are few, if any, symptoms in the early stage. Blindness can result if it is left untreated. Like most types of glaucoma, childhood glaucoma may run in families. Signs of this disease include:

• clouding of the cornea (the clear front part of the eye);
• tearing; and
• an enlarged eye.

How is glaucoma diagnosed?

Because it has no noticeable symptoms, glaucoma is a difficult disease to detect without regular, complete eye exams.

Enlarged Cupping

During a glaucoma evaluation, your ophthalmologist will perform the following tests:

• Tonometry. Your ophthalmologist measures the pressure in your eyes (intraocular pressure, or IOP) using a technique called tonometry. Tonometry measures your IOP by determining how your cornea responds when an instrument presses on the surface of your eye. Eye drops are usually used to numb the surface of your eye for this test.

• Gonioscopy. For this test, your ophthalmologist inspects your eye’s drainage angle—the area where fluid drains out of your eye. During gonioscopy, you sit in a chair facing the microscope used to look inside your eye. You will place your chin on a chin rest and your forehead against a support bar while looking straight ahead. The goniolens is placed lightly on the front of your eye, and a narrow beam of light is directed into your eye while your doctor looks through the slit lamp at the drainage angle. Drops will be used to numb the eye before the test.

• Ophthalmoscopy. With this test, your ophthalmologist can evaluate whether or not there is any optic nerve damage by looking at the back of the eye (called the fundus). There are two types of ophthalmoscopy: direct and indirect. With direct ophthalmoscopy, your ophthalmologist uses a small flashlight-like instrument with several lenses that magnifies up to about 15 times. This type of ophthalmoscopy is most commonly done during a routine physical examination. With indirect ophthalmoscopy, the ophthalmologist wears a headband with a light attached and uses a small handheld lens to look inside your eye. Indirect ophthalmoscopy allows a better view of the fundus, even if your natural lens is clouded by cataracts.

• Visual field test. The peripheral (side) vision of each eye is tested with visual field testing, or perimetry. For this test, you sit at a bowl-shaped instrument called a perimeter. While you stare at the center of the bowl, lights flash. Each time you see a flash, you press a button. A computer records your response to each flash. This test shows if you have any areas of vision loss. Loss of peripheral vision is often an early sign of glaucoma.

• Photography. Sometimes photographs or other computerized images are taken of the optic nerve to inspect the nerve more closely for damage from elevated pressure in the eye.
• Pachymetry. This determines the thickness of your cornea. Recent studies have shown that corneal thickness can influent the measurement of IOP. Thicker cornea may give falsely high reading and thinner cornea can give falsely low reading.

• Special imaging – Optical coherence tomography (OCT). This is a laser scanner that is used to better determine the configuration of the optic nerve head and retinal nerve fiber layer in micrometers. This new technology is able to obtain sub-surface images of translucent or opaque materials at a resolution equivalent to a low-power microscope. It is effectively ‘optical ultrasound’, imaging reflections from within tissue to provide cross-sectional images.

Each of these evaluation tools is an important way to monitor your vision to help ensure that glaucoma does not rob you of your sight. Some of these tests will not be necessary for everyone. Your ophthalmologist will discuss which tests are best for you. Some tests may need to be repeated on a regular basis to monitor any changes in your vision caused by glaucoma.

How is glaucoma treated?

The goal of glaucoma treatment is to lower your eye pressure to prevent or slow further vision loss. Your ophthalmologist will recommend treatment if the risk of vision loss is high. Treatment often consists of eye drops but can include laser treatment or surgery to create a new drain in the eye. Glaucoma is a chronic disease that can be controlled but not cured. Ongoing monitoring (every three to six months) is needed to watch for changes. Ask your ophthalmologist if you have any questions about glaucoma or your treatment.

Medication:

These eye drops work by reducing the production of the aqueous humor into the eye or increasing the outflow of aqueous humor away from the eye.

• Beta blockers (Timolol, levobunolol, carteolol, metipranolol, betaxolol)
• Prostaglandin (latanoprost, travoprost, brimatoprost)
• Adrenergic agonists (bromonidine, apraclonidine)
• Carbonic anhydrase inhibitors (brinzolamide, dorzolamide)
• Parasympathomimetic agents (pilocarpine)

Laser:

These are quick, painless, and relatively safe procedures.

• Laser iridotomy involves creating a hole in the iris to allow fluid to drain in narrow or closed angle glaucoma.
• Laser trabeculoplasty creates larger opening pores in the trabecular meshwork to allow the aqueous humor to percolate away from the eyes. It’s usually done in open angle or normal tension glaucoma.
• Laser cilioablation is another form of laser that’s reserved for severe form of glaucoma with poor visual potential. These laser burns destroy the cells that make the aqueous fluid, thereby, reducing the IOP. This is done only other more traditional therapies have failed.

Glaucoma surgery:

Trabeculectomy

If you have glaucoma and medications and laser surgeries do not lower your eye pressure adequately, your ophthalmologist may recommend a procedure called a trabeculectomy.

In this procedure, a tiny drainage hole is made in the sclera (the white part of the eye). The new drainage hole allows fluid to flow out of the eye into a filtering area called a bleb. The bleb is mostly hidden under the eyelid. When successful, the procedure will lower your intraocular pressure (IOP), minimizing the risk of vision loss from glaucoma. The surgery is performed in an operating room on an outpatient basis.

Shunts devices:

In cases of severe open-angle glaucoma or chronic (long-term) glaucoma, if your eye is at high risk for scarring and your IOP needs to be lowered to preserve your vision, your ophthalmologist may recommend placing a tiny drainage tube in your eye called a Seton.

The drainage tube creates a new channel for fluid to flow from the eye to a filtering area, called a bleb. A tiny plate placed on the eye helps the bleb form and remain open. The tube is covered with a patch and is typically not seen or felt. This procedure is performed in the operating room on an outpatient basis.