Glaucoma
Both cataracts and glaucoma can be a natural part of the aging process. Many people over 60 may have both, but the two conditions are not related. Glaucoma does not cause cataracts and cataracts do not cause glaucoma. Both cataracts and glaucoma are serious conditions that can cause vision loss. However, loss of vision due to cataracts can be reversed with surgery. Loss of vision from glaucoma is irreversible.
Glaucoma is a group of eye diseases that cause damage to the optic nerve that carries images to the brain. Glaucoma comes on gradually without warning and often without symptoms.
Glaucoma is caused by increased pressure within the eye. A backup of fluid in the eye causes this elevated pressure. When the pressure in the eye builds, the optic nerve cells become compressed causing them to become damaged and eventually die. This damage results in permanent visual loss. Early diagnosis and treatment of glaucoma can help prevent or minimize vision loss.
The most common form of glaucoma, called primary open angle glaucoma, affects about three million Americans. In primary open angle glaucoma, the eye’s drainage canals become clogged over time. The inner eye pressure (also called intraocular pressure or IOP) rises because the correct amount of fluid can’t drain out of the eye. The clogging problem occurs inside the drainage canals not at the entrances to the drainage canals, which remain clear and work normally.
Forms of Glaucoma
Primary open angle glaucoma develops slowly and sometimes without noticeable sight loss for many years. Most people have no symptoms and no early warning signs. If open angle glaucoma goes undetected and untreated, it can cause a gradual loss of vision. Open angle glaucoma usually responds well to medication, usually in the form of eye drops, especially if diagnosed in its early stages.
Acute glaucoma or narrow angle glaucoma is more rare and is very different from open angle glaucoma in that the eye pressure usually goes up very fast. With angle closure glaucoma, the outer edge of the iris bunches up over the drainage canals, when the pupil enlarges too much or too quickly, usually when adjusting to low light situations. Symptoms of angle closure glaucoma may include headaches, eye pain, nausea, and rainbows around lights at night, and very blurred vision. Treatment of angle closure glaucoma usually involves surgery to remove a small portion of the outer edge of the iris.
It was once thought that high intraocular pressure (IOP) was the only cause of the optic nerve damage of glaucoma. Although IOP is clearly a risk factor, persons with “normal” IOP can also experience vision loss from glaucoma. This form of glaucoma is known as low tension glaucoma or normal pressure glaucoma. The causes of optic nerve damage in low tension glaucoma is unknown and patients have “normal” pressure levels. Those at higher risk for this form of glaucoma are people with a family history of normal tension glaucoma, people of Japanese ancestry, and people with a history of systemic heart disease, such as irregular heart rhythm. Normal tension glaucoma is usually detected after an examination of the optic nerve.
The eye drops that lower IOP in other forms of glaucoma are also effective in cases of normal tension glaucoma. Currently, most doctors treat normal tension glaucoma by keeping normal eye pressures as low as possible with medicines, laser surgery, or filtering surgery.
Secondary glaucoma can occur as the result of an eye injury, inflammation, tumor or in advanced cases of cataract or diabetes. It can also be caused by the use of certain drugs such as steroids. This form of glaucoma may be mild or severe. Secondary glaucoma can be either open angle or angle closure glaucoma. The common forms of secondary glaucoma are pigmentary glaucoma, traumatic glaucoma, pseudoexfoliative glaucoma, and neovascular glaucoma.
Pigmentary glaucoma occurs when the pigment granules in the back of the iris, the colored part of the eye, break into the clear fluid produced inside the eye. Tiny pigment granules flow toward the drainage canals in the eye and slowly clog the canals, causing eye pressure to rise. Treatment usually includes medications or surgery.
Traumatic glaucoma is caused by an injury to the eye. This type of glaucoma can occur both immediately after an injury to the eye or years later. It can be caused by blunt trauma injuries that “bruise” the eye or injuries that penetrate the eye. Conditions such as severe nearsightedness, previous injury, infection or prior surgery may also make the eye more vulnerable to traumatic glaucoma.
Pseudoexfoliative glaucoma occurs when a flaky, dandruff-like material peels off the outer layer of the lens within the eye. The material collects in the angle between the cornea and iris and can clog the drainage system of the eye, causing eye pressure to rise. This form of secondary glaucoma is most common in those of Scandinavian descent. Treatment usually includes medications or surgery.
Neovascular glaucoma is caused by the abnormal formation of new blood vessels on the iris and over the eye’s drainage channels. This type of glaucoma is always associated with other medical conditions, most often diabetes. The new blood vessels prevent the eye’s fluid from exiting through the trabecular meshwork, causing an increase in eye pressure. This type of glaucoma is very difficult to treat.
Irido Corneal Endothelial Syndrome (ICE) is a rare form of glaucoma that usually is found in only one eye. In this type of glaucoma, cells on the back surface of the cornea spread over the eye’s drainage tissue and across the surface of the iris, causing an increase in eye pressure, which can damage the optic nerve. These cells also form adhesions that bind the iris to the cornea, further blocking the drainage channels. ICE occurs more frequently in light-skinned females. Symptoms can include hazy vision upon awakening and the appearance of halos around lights. ICE is difficult to treat and laser therapy is not an effective therapy. ICE is usually treated with medications and/or filtering surgery.
