Types Of Glaucoma

The two major categories of glaucoma are open-angle glaucoma (OAG) and narrow angle glaucoma. The "angle" in both cases refers to the drainage angle inside the eye that controls the outflow of the watery fluid (aqueous) that is continually being produced inside the eye.

If the aqueous can access the drainage angle, the glaucoma is known as open angle glaucoma. If the drainage angle is blocked and the aqueous cannot reach it, the glaucoma is known as narrow angle glaucoma.

• Primary open-angle glaucoma.

  This common type of glaucoma gradually reduces your peripheral vision without other symptoms. By the time you notice it, permanent damage already has occurred.

  If your IOP remains high, the destruction caused by POAG can progress until tunnel vision develops, and you will be able to see only objects that are straight ahead. Ultimately, all vision can be lost, causing blindness.

• Acute angle-closure glaucoma.

  Also called narrow-angle glaucoma, acute angle-closure glaucoma produces sudden symptoms such as eye pain, headaches, halos around lights, dilated pupils, vision loss, red eyes, nausea and vomiting.

  These signs constitute a medical emergency. The attack may last for a few hours, and then return again for another round, or it may be continuous without relief. Each attack can cause progressively more vision loss.

• Normal-tension glaucoma.

  Like POAG, normal-tension glaucoma (also called normal-pressure glaucoma, low-tension glaucoma or low-pressure glaucoma) is a type of open-angle glaucoma that can cause visual field loss due to optic nerve damage. But in normal-tension glaucoma, the eye's IOP remains in the normal range.

  Also, pain is unlikely and permanent damage to the eye's optic nerve may not be noticed until symptoms such as tunnel vision occur.

  The cause of normal-tension glaucoma is not known. But many doctors believe it is related to poor blood flow to the optic nerve. Normal-tension glaucoma is more common in those who are Japanese, are female and/or have a history of vascular disease.

• Pigmentary glaucoma.

  This rare form of glaucoma is caused by clogging of the drainage angle of the eye by pigment that has broken loose from the iris, reducing the rate of aqueous outflow from the eye. Over time, an inflammatory response to the blocked angle damages the drainage system.

  You are unlikely to notice any symptoms with pigmentary glaucoma, though some pain and blurry vision may occur after exercise. Pigmentary glaucoma most frequently affects white males in their mid-30s to mid-40s.

• Secondary glaucoma.

  Symptoms of chronic glaucoma following eye injury could indicate secondary glaucoma, which also may develop with presence of eye infection, inflammation, a tumor or enlargement of the lens due to a cataract.

• Congenital glaucoma.

  This inherited form of glaucoma is present at birth, with 80 percent of cases diagnosed by age one. These children are born with narrow angles or some other defect in the drainage system of the eye.

It's difficult to spot signs of congenital glaucoma, because children are too young to understand what is happening to them. If you notice a cloudy, white, hazy, enlarged or protruding eye in your child, consult your eye doctor. Congenital glaucoma typically occurs more in boys than in girls.

Diagnosis, Screening And Tests For Glaucoma

During routine eye exams, a tonometer is used to measure your intraocular pressure, or IOP. Your eye typically is numbed with eye drops, and a small probe gently rests against your eye's surface. Other tonometers send a puff of air onto your eye's surface. An abnormally high IOP reading indicates a problem with the amount of fluid (aqueous humor) in the eye. Either the eye is producing too much fluid, or it's not draining properly. Normally, IOP should be below 20 mmHg .

If your IOP is higher than 30 mmHg, your risk of vision loss from glaucoma is 40 times greater than someone with intraocular pressure of 15 mmHg or lower. This is why glaucoma treatments such as eye drops are designed to keep IOP low.

Other methods of monitoring glaucoma involve the use of sophisticated imaging technology — such as scanning laser polarimetry (SLP), optical coherence tomography (OCT) and confocal scanning laser ophthalmoscopy — to create baseline images and measurements of the eye's optic nerve and internal structures.

Visual field testing is a way for your eye doctor to determine if you are experiencing vision loss from glaucoma. The visual field test may be repeated at regular intervals to make sure you are not developing blind spots from damage to the optic nerve or to determine the extent or progression of vision loss from glaucoma.

Gonioscopy also may be performed to make sure the aqueous humor (or "aqueous") can drain freely from the eye. In gonioscopy, special lenses are used with a biomicroscope to enable your eye doctor to see the structure inside the eye (called the drainage angle) that controls the outflow of aqueous and thereby affects intraocular pressure. Ultrasound biomicroscopy is another technique that may be used to evaluate the drainage angle.

Glaucoma Treatment

Treatment can involve lasers, medication, glaucoma surgery, depending on the severity. Eye drops with medication aimed at lowering IOP usually are tried first to control glaucoma.

Because glaucoma often is painless, people may become careless about strict use of eye drops that can control eye pressure and help prevent permanent eye damage.

Non-compliance with a program of prescribed glaucoma medication is a major reason for blindness caused by glaucoma.

If you find that the eye drops you are using for glaucoma are uncomfortable or inconvenient, never discontinue them without first consulting your eye doctor about a possible alternative therapy.