Glaucoma - The Basics  | Intraocular Glaucoma | Neovascular Glaucoma | Normal-Tension Glaucoma | Optic Disc Photographs | Peripheral Iridotomy | Selective Laser Trabeculoplasty | Transscleral Cyclophotocoagulation (G6) |  Trabeculectomy | Visual Field Testing

Glaucoma—The Basics

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 blind spots and vision loss.

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 optic nerve and lead to vision loss.

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 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 (Eye M.D.) may recommend treatment to lower your IOP to prevent future damage.

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.

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.

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.

Your ophthalmologist may tell you that you are at risk for glaucoma if you have one or more risk factors, including having an elevated IOP, a family history of glaucoma, certain optic nerve conditions, are of a particular ethnic background, or are of advanced age. Regular examinations with your ophthalmologist are important if you are at risk for this condition.

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 eyedrops 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.

Intraocular Pressure

Elevated intraocular pressure (high pressure within the eye) is the number one risk factor for glaucoma. However, elevated intraocular pressure (IOP) does not always cause glaucoma.

The average eye pressure in adults ranges between 10 mm Hg and 21 mm Hg (“mm Hg” stands for “millimeters of mercury”). There can be a significant difference in your IOP throughout the course of a day. This variation is known as diurnal fluctuation. We know that many patients with IOP in the 20s do not develop glaucoma. Up to 50% of patients diagnosed with glaucoma have an initial pressure reading lower than 22 mm Hg. Intraocular pressure is not a very sensitive tool for diagnosing glaucoma, but it becomes very useful in monitoring treatment for glaucoma.

A variety of methods can be used to check the intraocular pressure, but the most common is applanation tonometry. Your ophthalmologist (Eye M.D.) will often set a “target” pressure for you and will work hard to keep the pressure at or below that target to help preserve your vision.

Neovascular Glaucoma

Neovascular glaucoma is a particularly aggressive and difficult to treat kind of glaucoma. It is caused by new, small blood vessels growing in the front part of the eye. These neovascularvessels grow on the surface of the iris (the colored part of the eye) and over the drainage channel, blocking the flow of fluid from the eye. This causes a rapid and painful rise in pressure within the eye. This type of glaucoma often does not respond well to medical treatment, and the high intraocular pressure can lead to a rapid loss of vision.

Causes of neovascular glaucoma include diabetic retinopathy, vein and artery occlusions, carotid artery disease, and many other conditions. The prognosis for neovascular glaucoma is poor. The goal of treatment is to minimize the factors that have caused the neovascularization, usually using a laser treatment called panretinal photocoagulation or anti-VEGF injections.

If the high eye pressure persists, treatment can include medication or surgery. When surgery is recommended, a particular type of medication therapy called antimetabolite therapy improves the chances of success. Because of the risk of scarring, seton surgery is often recommended.

The goal in treating neovascular glaucoma is to lower the intraocular pressure, preserve vision, and maintain a comfortable eye.

Normal-Tension Glaucoma

Normal-tension glaucoma typically means that glaucoma damage has been detected in an eye with so-called "normal" intraocular pressure (IOP)-that is, an eye that has not had documented pressure above 20 mm Hg. Ophthalmologists increasingly believe that this condition is a continuum of the same glaucoma process seen in those people with higher IOP.

Normal-tension glaucoma is diagnosed by examining the appearance of the optic nerve or by detecting abnormalities on visual field tests.

One large study showed that progressive damage and visual field loss can be significantly reduced in people with normal-tension glaucoma by lowering their IOP by 30% or more.

Other conditions can sometimes be mistaken for normal-tension glaucoma, so thorough eye and medical examinations are often required to make this diagnosis. Often the IOP will be measured at different times during the day to see if there are any pressure elevations. Other tests may also be necessary.

If your ophthalmologist (Eye M.D.) believes that you have normal-tension glaucoma, he or she may begin treatments to lower your IOP. This can be done with medications, laser treatment, or surgery.

Patients with adequately treated normal-tension glaucoma have a good prognosis, especially when the disease is caught early in its course.

Optic Disc Photographs

Photographic images of the optic disc are essential for monitoring glaucoma.

Glaucoma damage is seen clinically as loss of the nerve fiber layer and an associated thinning of tissue at the optic nerve head. With this damage, ophthalmologists (Eye M.D.s) look for what they call “cupping” of the optic nerve. Stereoscopic disc photos of the optic nerve are helpful in providing a baseline of information about the optic nerve’s condition for future comparison. These photographs are taken in the ophthalmologist’s office using a special camera that can create a stereo image.

Because one ophthalmologist may interpret the appearance of optic nerve cupping differently from another ophthalmologist, optic disc photography is invaluable because it helps create a baseline for future comparison. Your ophthalmologist later may take additional pictures for side-by-side comparison. These can help identify signs of glaucoma progression.

Despite many new imaging techniques for glaucoma, disc photos and a careful clinical examination are still the standard of care for glaucoma.

Peripheral Iridotomy

If your ophthalmologist (Eye M.D.) suspects that you have “narrow” or “closed” angles, this means that the drainage channel of your eye is blocked or nearly blocked, placing you at high risk for elevated intraocular pressure and vision loss. This is called angle-closure glaucoma.

An acute attack of angle-closure glaucoma is marked by very high eye pressure and complete blockage of the drainage channel in the eye. Symptoms include pain, red eye, and decreased vision.

To treat angle-closure glaucoma, your ophthalmologist will perform a peripheral iridotomy (PI), creating a surgical opening within the upper part of the iris (the colored part of the eye) using a laser. This opening is typically so small that it cannot be seen with the naked eye. The opening in the iris allows fluid to flow from behind the iris through the opening, allowing the iris to fall back into a more normal position and opening the drain.

This laser treatment is always performed on an outpatient basis, often in the ophthalmologist’s office. The treatment will not improve your vision, but it can help prevent vision loss from a dangerous type of glaucoma. The side effects of the treatment can include the appearance of a “light streak,” a temporary rise in intraocular pressure, and inflammation.

Selective Laser Trabeculoplasty

Selective laser trabeculoplasty (SLT) is a laser surgical procedure used to help lower intraocular pressure (IOP) of patients with open-angle glaucoma. SLT is used to treat the eye’s drainage system, known as the trabecular meshwork—the mesh-like drainage canals that surround the iris. Treating this area of the eye’s natural drainage system improves the flow of fluid out of the eye, helping to lower the pressure.

The laser used in SLT works at very low levels. It treats specific cells selectively, leaving untreated portions of the trabecular meshwork intact. For this reason, SLT, unlike other types of laser surgery, may be safely repeated many times.

SLT is typically performed in the ophthalmologist’s (Eye M.D.’s) office or an outpatient surgery center. The procedure usually takes about five to ten minutes. First, anesthetic drops are placed in your eye. The laser machine looks similar to the examination microscope that your ophthalmologist uses to look at your eyes at each office visit.

You will experience a flash of light with each laser application. Most people are comfortable and do not experience any significant pain during the surgery, although some may feel a little pressure in the eye during the procedure.

Most people will need to have their pressure checked after the laser treatment, since there is a risk of increased eye pressure. 

 Transscleral Cyclophotocoagulation (G6) 

MicroPulse TSCPC, also knows as the G6 delivers repetitive, low-energy laser ‘micropulses’ which reduce risks associated with other destructive therapies.MicroPulse TSCPC is a noninvasive therapy thatdoes not require any incisions or implants.

The G6  can be performed in an office setting or in the operating room, as determined by the doctor. The procedure does not cause tissue damage, therefore the doctor may repeat it as needed for glaucoma management

Prior to MicroPulse TSCPC, anesthesia is used to make patients comfortable while the doctor gently moves the MP3 probe above and below the iris during surgery. Following the procedure, patients may wear a small eye patch for the rest of the day. Most patients do not experience pain after the therapy. Any mild discomfort or redness in the eye that may be experienced typically goes away within a few days. Short term use of an anti-inflammatory medicine is often prescribed to control inflammation.

Typically, IOP decreases a few weeks after the procedure. In time, it may be determined that MicroPulse TSCPC has reduced the need for glaucoma medications*. However, it is important for glaucoma patients to maintain regular appointments with an eye care doctor for monitoring and treatment of the disease

Trabeculectomy

If you have glaucoma and medications and laser surgeries do not lower your eye pressure adequately, your ophthalmologist (Eye M.D.) 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.

Some of the risks and complications from trabeculectomy surgery include the following:

• failure to control intraocular pressure, with the need for another operation;
• infection;
• bleeding in the eye;
• swelling in the eye;
• irritation or discomfort in the eye;
• eye pressure that is too low;
• cataract (in cases where cataract has not already been removed); and
• decreased or lost vision.

Antimetabolites
Certain medications, called antimetabolites, were originally developed to help treat some kinds of cancer. These same medications have also been found to be helpful when used with some types of glaucoma surgery.

These medicines may be applied to the eye during or after the surgery to reduce the growth of scar tissue, a common cause of failure in glaucoma surgery. Mitomycin-C and 5-fluorouracil (5-FU) are the most commonly used antimetabolites for glaucoma surgery. When these antimetabolites are used with other medications that reduce inflammation, the success rate of surgery is greatly improved, especially for patients who are at high risk for excessive scarring.

Your ophthalmologist may consider using antimetabolite medicines with your glaucoma surgery if:

• you are having surgery on an eye that has been operated on before;
• you have inflammation in your eye (called uveitis);
• you have glaucoma due to new blood vessel formation within the eye;
• you are having glaucoma and cataract surgery at the same time;
• you are relatively young;
• you have more deeply pigmented skin; or
• your eyes are at risk for postoperative scarring.

In addition to the usual complications of glaucoma surgery, other risks associated with using antimetabolites include:

• eye pressure that is too low;
• leaking incisions;
• slower healing of the cornea;
• blurred vision;
• fluid in or behind the retina;
• thinning of the eye tissues; and
• infection.

If your ophthalmologist has decided to use antimetabolite medications, he or she will explain why they are recommended for you.

While some people may experience side effects from medications or surgery, the risks associated with these side effects should be balanced against the greater risk of leaving glaucoma untreated and losing your vision.

Visual Field Testing

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

One particular test, called a visual field test (orperimetry test), measures all areas of your eyesight, including your side, or peripheral, vision. A visual field test can help find certain patterns of vision loss and is a key way to check for glaucoma. It is very useful in finding early changes in vision caused by nerve damage from glaucoma.

To take this painless 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 the location of each flash and whether you pressed the button when the light flashed in that location. At the end of the test, a printout shows if there are areas of your field of vision where you did not see the flashes of light. This test shows if you have any areas of vision loss. Loss of peripheral vision is often an early sign of glaucoma. Regular perimetry tests are an important technique for learning how, if at all, your vision is changing over time. It can also be used to see if treatment for glaucoma is preventing further vision loss.