• Open angle or chronic glaucoma
• Closed angle or acute glaucoma
• Congenital glaucoma
• Secondary glaucoma

All four types are characterized by increased pressure within the eyeball, and therefore all of them can cause progressive damage to the optic nerve. Increased pressure occurs when the fluid within the eye (called aqueous humor), which is produced continuously, does not drain properly. The pressure pushes on the junction of the optic nerve and the retina at the back of the eye. This reduces the blood supply to the optic nerve, which carries vision from the eye to the brain. This loss of blood supply causes the individual nerve cells to progressively die. As the optic nerve deteriorates, blind spots develop in the field of vision. Peripheral vision (side vision) is affected first followed by front or central vision. Without treatment, glaucoma can eventually cause blindness.

Acute glaucoma may occur in persons who were born with a narrow angle between the iris and the cornea (the anterior chamber angle). This is more common in farsighted eyes. The iris may slip forward and suddenly close off the exit of aqueous humor, and a sudden increase in pressure within the eye follows. Symptoms of pain, redness, nausea, and visual loss develop rapidly. Angle closure may be provoked by the use of drops that dilate the eyes in susceptible persons. Attacks may also develop without any obvious triggering event. This is more common in the evening because the eye's pupils naturally dilate in dim light.

Chronic open angle glaucoma is by far the most common type of glaucoma. In open angle glaucoma, the iris does not block the drainage angle as it does in acute glaucoma. The fine fluid outlet channels within the wall of the eye gradually narrow with time. The disease usually affects both eyes, and over a period of years the consistently elevated pressure slowly damages the optic nerve. Chronic glaucoma has no early warning signs, and the associated loss of peripheral vision occurs so gradually that it may go unnoticed until a substantial amount of damage and vision loss have occurred. The only way to diagnose glaucoma early is through routine eye examinations. 

Secondary glaucoma is caused by other diseases including some eye diseases (uveitis) and systemic diseases, and by some drugs (corticosteroids).

Congenital glaucoma, present at birth, is the result of defective development of the fluid outflow channels of the eye. Surgery is required for correction. Congenital glaucoma is often hereditary.

Risk factors depend on the type of glaucoma. For chronic glaucoma, the risk factors include; age over 40, a family history of glaucoma, diabetes, and nearsightedness. People with a family history of open angle glaucoma have twice the risk of developing open angle glaucoma as those who do not.  African-Americans have four times the risk of developing open angle glaucoma as compared to Americans of European decent. It is estimated that 1 to 2% of people over 40 have chronic glaucoma with about 25% of cases undetected.

The risk factors for acute glaucoma are: family history of acute glaucoma, older age, farsightedness, and the use of systemic anticholinergic medications (such as atropine or eye dilation drops) in a high-risk individual. Acute, congenital, and secondary glaucoma are much less common than chronic glaucoma.

Ency. home > Disease > G > Glaucoma

[an error occurred while processing this directive]