Glaucoma is a specific pattern of diseases that damage the optic nerve, the big bundle of nerves that carries the images we see to the brain.  As many people know, glaucoma has something to do with pressure inside the eye (intraocular pressure), and that the higher the pressure inside the eye, the greater the chance of damage to the optic nerve.  It is not true, however, that high intraocular pressure (IOP) necessarily causes nerve damage, or that it is a major symptom or indicator of glaucoma.  A person with high IOP should still be watched closely, however, since there still remains a chance that glaucoma may develop.

What Causes Glaucoma?
Pressure builds up in the eye when the clear liquid called the aqueous humor, which normally flows in and out of the eye, is prevented from draining properly.  This can happen in different ways, depending on the type of glaucoma.  The resulting increase in pressure within the eye can damage the optic nerve.

Ophthalmologists used to think that high intraocular pressure was the main cause of optic nerve damage in glaucoma, however, we now know that even people with "normal" IOP can experience vision loss from glaucoma -- so-called "normal tension glaucoma."

There may be other factors which affect the optic nerve, even when IOP is in the so-called "normal" range.  Elevated IOP is still considered a major risk factor for glaucoma, though, because studies have shown that the higher IOP is, the more likely optic nerve damage to occur.  If the entire nerve is destroyed, blindness results.

What are the Symptoms?
The reason glaucoma causes blindness in so many cases is that most people do not even notice any problems until some degree of damage has already occurred and some vision is lost.

As optic nerve fibers are damaged by glaucoma, small blind spots may begin to develop, usually in the side, or peripheral vision. Many people do not notice the blind spots until significant optic nerve damage has already occurred.

One type of glaucoma (acute angle-closure glaucoma) does not even produce noticeable symptoms until it has become a big problem.  There is a sudden build-up of IOP, which may cause any of the following symptoms:  blurred vision, severe eye pain, headache, rainbow haloes around lights, nausea, and vomiting.

Acute angle-closure glaucoma is a rare and severe form of glaucoma.  If you have any of these symptoms, you need to call your ophthalmologist immediately.  Unless a doctor treats acute angle-closure glaucoma quickly, blindness can result.

The different types of Glaucoma
The most common glaucoma is called open-angle glaucoma, which occurs as a result of aging.  The drainage angle of the eye becomes less efficient with time, and pressure within the eye gradually increases.

If this increased pressure results in optic nerve damage, it is known as chronic open-angle glaucoma.  This form of glaucoma can damage vision so gradually and painlessly that you are not aware of trouble until the optic nerve is already badly damaged.  Over 90% of adult glaucoma patients have open-angle glaucoma.

In angle-closure glaucoma, the normal drainage canals are blocked when the area between the iris and the cornea is not open.  This condition can be chronic (progressing slowly or occurring persistently) or acute (occurring suddenly).

In acute angle-closure glaucoma, there is a sudden increase in intraocular pressure (IOP) due to the buildup of aqueous in the eye.

Chronic angle-closure glaucoma, like open-angle glaucoma, may cause vision damage without symptoms.  On the other hand, acute angle-closure glaucoma is considered an emergency situation because optic nerve damage and subsequent vision loss can occur within hours of the onset of the problem.

"Normal (or low) tension" glaucoma is an unusual and poorly understood form of the disease.  In this type of glaucoma, the optic nerve is damaged even though the patient's intraocular pressure is consistently within a range usually considered normal.

Childhood glaucoma is rare and starts in infancy, childhood, or adolescence.  Like open-angle glaucoma, there are few, if any, symptoms in the early stage, and blindness can result if it is left untreated.  Like most types of glaucoma, this type is thought to have a hereditary component.

Congenital glaucoma is a type of childhood glaucoma that usually appears soon after birth, although it can become apparent later in the first year of life.  Unlike other childhood glaucomas, congenital glaucoma often has noticeable signs, including tearing, light sensitivity, and cloudiness of the cornea.  This type of glaucoma is more common in boys, and can affect one or both eyes.

Detection of Glaucoma
Regular eye examinations are the best way to detect glaucoma.  Your doctor uses several different instruments and techniques to check your intraocular pressure, inspect the drainage angle of your eye, evaluate any optic nerve damage, and test the visual field of each eye.

Some of these tests may not be necessary for every person, but some people may need to repeat these tests on a regular basis to determine if damage from glaucoma is increasing over time.

Risk Factors for Glaucoma
High IOP alone does not mean that you have glaucoma.  Your doctor puts together many pieces of information to determine your risk for developing the disease.  The most important of these risk factors include:

• Age
• Nearsightedness
• African ancestry
• A family history of glaucoma
• Past injuries to the eye
• A history of severe anemia or shock

Your doctor will weigh all of these factors before deciding whether you need treatment for glaucoma, or whether you should be monitored closely.

Treatment
Damage caused by glaucoma is, as a rule, not reversible, and no cure has yet been found for glaucoma.  Glaucoma can, however, be held in check with eye drops, pills, and laser or surgical operations that can be used to prevent or slow further damage from occurring.  With any type of glaucoma, periodic examinations are very important to prevent vision loss, even when treatment is successful.  Because glaucoma can worsen without you being aware of it, your treatment may need to be changed over time.

Treatment for glaucoma is focused on lowering IOP to a level the doctor thinks will not be likely to cause further damage in the optic nerve.  This level (sometimes referred to as the "target level") varies from person to person and may even vary over time for an individual.

Medicines
Open-angle glaucoma is usually controlled with medicine that will lower the IOP and may take the form of pills, eye drops, ointments, or inserts (wafer-like strips placed in the corner of the eye).  These medications reduce IOP by decreasing the production of aqueous humor or by increasing the flow through the drainage angle.

Glaucoma medications can have side effects, as can any medication.  You should notify your doctor if you think you may be experiencing side effects including, but not limited to:  a stinging sensation in the eyes, red eyes, blurred vision, headaches, changes in pulse, heartbeat or breathing, tingling of fingers and toes, drowsiness, loss of appetite, bowel irregularities, kidney stones, or anemia or easy bleeding.

Surgery
For many people, surgery may be the best treatment for their glaucoma.  There are several different types of surgery for glaucoma.  The kind of surgery that is right for you will be determined by you and your doctor after considering a number of factors, including the type and severity of glaucoma, overall health, and other eye conditions.  Depending on the type of surgery you and your doctor decide upon, it may be performed with either a laser or conventional surgical procedure.

Laser Surgery
The laser can be used in three different ways when treating glaucoma.

Trabeculoplasty is used most often to treat open-angle glaucoma.  In this procedure, a laser is used to place "spot welds" in the drainage area of the eye, known as the trabecular meshwork, that allow the aqueous to drain more freely.

Iridotomy is frequently used to treat angle-closure glaucoma.  In this procedure, the surgeon uses the laser to make a small hole in the iris, which allows the aqueous to flow more freely within the eye and through the trabecular meshwork.

Cyclophotocoagulation is a slightly more drastic procedure which may be used to treat more advanced or aggressive cases of glaucoma.  In this procedure, a laser beam is used to treat selected areas of the ciliary body, the part of the eye that produces aqueous humor, to reduce the production of fluid and thus lower the pressure within the eye.

Laser surgery is usually performed in an outpatient surgery center or the doctor’s office and requires only light anesthesia and a generally short recovery time.  Patients may experience some irritation in their eyes, but can usually resume their normal activities within one or two days.

Incisional Surgery
In some cases, laser surgery is not the preferred surgical treatment for glaucoma.  Sometimes, when vision loss is rapid, or medication and/or laser surgery fails to lower IOP sufficiently, "conventional" incisional surgery is the best option.

Filtering surgery is usually done in a hospital or outpatient surgery center with local anesthesia, and sometimes, sedation.  The surgeon uses very delicate instruments to remove a tiny piece of the wall of the eye (the sclera), leaving a tiny hole.  The aqueous can then drain through the hole and be reabsorbed into the bloodstream, thus reducing the intraocular pressure.

In some cases, the surgeon may place a small tube or valve in the eye through a tiny incision in the sclera.  The valve acts as a regulator for the buildup of aqueous within the eye.  When the intraocular pressure reaches a certain level, the valve opens, allowing the fluid to flow out of the eye's interior, where it can be reabsorbed by the body.  The procedure may take place in the ophthalmologist's office or outpatient surgical center, and can be done under local anesthesia.

The recuperative period following incisional glaucoma surgery is usually short.  You may need to wear an eye patch for a few days after surgery and to avoid activities which expose the eye to water, such as showering or swimming.  The ophthalmologist may recommend you refrain from heavy exercise, straining, or driving for a short time after surgery to avoid complications.

As with any surgery, patients should be aware that there are risks associated with glaucoma surgery.  Complications are not likely, but may include infection, bleeding, undesirable changes in IOP, and, in some cases, loss of vision.

Sometimes, a single surgical procedure will not effectively halt the progress of a patient’s glaucoma. In these cases a repeat surgery may be scheduled and continued treatment by medication may be prescribed.