There are several kinds of glaucoma. The two major types are primary open-angle glaucoma (POAG) and angle-closure or narrow-angle glaucoma. There are also several secondary types.

• Primary open-angle glaucoma (POAG) is the most common form of glaucoma, and it afflicts about 2.2 million people in the U.S. It is the most common form of glaucoma in Caucasians and those of African descent. With POAG, the entrances to the drainage canals usually remain open, but the disease develops as the canals that drain fluid become clogged, which causes inner eye pressure to rise. POAG typically has no symptoms and can develop over several years with no loss of vision. It gradually reduces vision if it is not diagnosed and treated. If diagnosed early, it usually responds well to treatment.
  
• Angle-closure glaucoma may develop gradually or quickly. If it develops suddenly, it may be called acute glaucoma or narrow-angle glaucoma, which is a medical emergency requiring immediate attention. This form of glaucoma is more common in people of Chinese ancestry. In the U.S., it is less frequent than POAG and very different from it in that the eye pressure usually increases quickly. With angle-closure glaucoma, the angle between the iris and cornea becomes narrow or obstructed so that aqueous pressure builds to levels high enough to damage the optic nerve before draining.
  
  This condition tends to occur in far-sighted eyes, which may be slightly smaller than others and have more crowded internal structures. Under some circumstances, such as when one enters a dark room, the pupil (the opening in the central part of the iris) dilates (opens) causing the outer edge of the iris to gather and fold, blocking the entrance to the drainage canals. Certain medications, including some over the counter cold and sinus remedies may provoke such a blockage. When purchasing drugs, always be sure to discuss side effects with your pharmacist.
  
  Surgery (typically laser therapy) to remove a small portion of the outer edge of the iris is usually performed to treat angle-closure glaucoma. The removal of the excess tissue prevents blockage of the angle, allowing normal fluid drainage. Angle-closure glaucoma may lead to symptoms such as nausea, headache, pain, blurry vision, and rainbow-like colors around lights at night.
  
• Normal-tension glaucoma, also known as low-tension glaucoma, is diagnosed in patients who have two of the three main signs of glaucoma: loss of optic nerve head tissue or cupping and visual field loss without high intraocular pressure. People at higher risk for this form of glaucoma are those with a family history of this condition, those who have a history of migraine headache and poor circulation, and people of Japanese ancestry.
  
• Secondary glaucoma is a term for a variety of other forms of glaucoma. Typically, it occurs when the flow of aqueous from the eye is impaired. It can result from a disorder present locally in the eye such as inflammation or a tumor, an eye injury, advanced cataracts or diabetes, and certain drugs such as steroids.
  
  Treatment for secondary forms of glaucoma depends on the precipitating cause. Once the underlying cause of increased intraocular pressure is corrected or cured (e.g., removal of a tumor), the pressure may return to normal and continued treatment with medication may not be needed. However, if optic nerve damage occurs, visual field loss will remain.
  
• Pseudoexfoliation glaucoma is associated with the formation of flakes of granular material at the edges of the pupil and throughout the inner surface of the front part of the eye. It is the most common identifiable form of secondary open-angle glaucoma worldwide. The glaucoma develops as the aqueous picks up flakes of material as it flows through the front part of the eye and deposits them in the trabecular meshwork tissue and drainage canals. Over time, these deposits build up and block drainage of aqueous, which increases intraocular pressure. This condition is treated with drugs and surgery. The glaucoma associated with this condition usually develops in people in their 70s and 80s.
  
• Pigmentary glaucoma is a form of open-angle glaucoma. It develops as the aqueous picks up pigment granules that break off the back of the iris and deposits them in the meshwork tissue and drainage canals. The deposits build up and block drainage of aqueous, which increases intraocular pressure. This condition is treated with drugs and surgery. It is usually seen in young and middle-aged people who are near-sighted. It is slightly more prevalent in men than in women.
  
• Primary congenital glaucoma affects infants. Most cases are detected during the first few months of life. Congenital glaucoma occurs when the trabecular meshwork does not fully open in the developing fetus, causing drainage to be impeded and fluid pressure to build. The elasticity of an infant’s eye, coupled with increased pressure, may cause the eye to enlarge and stretch. The stretching can cause the cornea to cloud. If a child’s eye is cloudy, white, hazy, or enlarged, a pediatrician or ophthalmologist should be contacted immediately.

Cataracts and glaucoma are two eye diseases often associated with advancing age. Many older people have both conditions. With relatively rare exceptions, cataracts do not cause glaucoma and glaucoma does not cause cataracts. The frequency of both conditions occurring in older people underscores the need for regular eye examinations.