Glaucoma is a slowly progressive eye condition that causes damage to the optic nerve. It is the leading cause of blindness among African-Americans and older adults in the United States. Because there are usually no symptoms early on in the disease, about half of the people with glaucoma do not even know they have it.
Over two million people in the United States have glaucoma, and 80,000 of those are legally blind as a result of the disease. Glaucoma can strike any age group, even newborn infants. Susceptibility to the disease increases with age. African-Americans are at a three times higher risk of glaucoma than the rest of the population.
There are at least 20 different types of glaucoma. These can be divided into four main types:
- Open-angle glaucoma. Accounts for over 60–70% of all cases. It is usually chronic and often bilateral.
- Closed-angle glaucoma. Usually an acute condition, as opposed to open-angle glaucoma that is chronic.
- Congenital glaucoma occurs in infants, usually under the age of one.
- Secondary glaucoma may be associated with eye diseases, other diseases, and certain types of medications.
Causes & symptoms
Glaucoma is the result of disruptions of normal processes to maintain pressure within the eye tissue. The iris, cornea, and lens of the eye are bathed in a nutritive liquid called the aqueous humor, which is made by cells within the eye. Excess fluid is continually removed by a spongy meshwork of drainage canals. Glaucoma occurs if there is a build up of the aqueous humor due to poor drainage or overproduction. As the fluid builds up there is increased pressure on the retina at the back of the eye. This increases the pressure, reducing the blood supply to the nerves of the retina, causing the nerves to die. This may distort and destroy the optic nerve. As nerve cells are destroyed, blind spots develop, and there is a progressive loss of vision. A change in the production and strength of collagen may also contribute to the onset of the disease. Collagen is a protein that helps maintain the structure and function of eye tissue. Stress and allergies may aggravate glaucoma symptoms.
It is probable that most cases of glaucoma are partially due to a genetic predisposition. At least 10 defective genes have been identified that may cause glaucoma. Although there are still many unknown factors that trigger the disease, a number of processes have been implicated. They include age-related changes, congenital abnormalities, injuries to the eye tissue, and problems related to other eye diseases. Vision loss in all forms of glaucoma is caused by damage to the optic nerve, the retina, and the collagen protein that makes up eye tissue. Use of certain medications, including antihypertensives, antihistamines, anticholinergics, and antidepressants may also contribute to the development of glaucoma. Corticosteroid eye drops, which are often used for other eye disorders, may destroy the integrity of eye tissue. Other types of eye drops may cause the pupils to dilate, increasing intraocular eye pressure (IOP), which may also lead to glaucoma in those who have a tendency to the disease.
Chronic open-angle glaucoma at first develops without noticeable symptoms. The pressure buildup is gradual and it does not bring on discomfort. Moreover, the vision loss is too gradual to be noticed at first, and the brain will compensate for blind spots. Over an extended period of time, the elevated pressure pushes against and damages the optic nerve and the retina. If glaucoma is left untreated, vision loss becomes evident and the condition becomes painful.
Acute closed-angle glaucoma is obvious from the beginning. The symptoms are blurred vision, severe eye pain, sensitivity to light, nausea and vomiting, dilated pupils, reddened eyes, and halos visualized around lights. The corneas may become hazy-looking. Acute closed-angle glaucoma is an emergency situation. It needs to be treated immediately. Congenital glaucoma is evident at birth. Symptoms are bulging eyes, cloudy corneas, enlarged corneas, excessive teariness, and sensitivity to light.
Risk factors that increase the probability of developing glaucoma include:
- ocular hypertension, a slightly increased IOP
- age over 40
- high blood pressure
- migraine headaches
- nearsightedness, farsightedness, and other visual disturbances
- a family history of glaucoma
- being of African-American ethnicity
Sometimes glaucoma can be diagnosed with a routine eye exam by an opthamologist, who can make a definitive diagnosis of glaucoma. IOP, defects in the field of vision, and the appearance of the optic nerve, are all considered in the diagnosis of glaucoma. Visual field tests can detect blind spots in a patient's field of vision before the patient is aware of them. An instrument, known as a tonometer, is used to measure eye pressure. Since IOP can vary throughout the day, a person may have to return for several visits to measure eye pressure at different times of the day. An ophthalmoscope is used to examine the inner aspects and the back of the eyes, including the optic nerve, for changes and damage. A slit lamp may be used to allow the doctor further examination of the eye. Another test, gonioscopy, can distinguish between narrow-angle and open-angle glaucoma. A gonioscope allows visualization of the angle between the iris and the cornea.
Vitamin C, taken in dosages up to bowel tolerance, is reported to reduce pressure within the eye and restore collagen balance. A vitamin C supplement with bioflavonoids, especially rutin and lutein, are particularly recommended. There is evidence that marijuana (Cannabis sativa) lowers IOP, as well. Although it is a controlled substance, marijuana can often be prescribed by a professional licensed to treat glaucoma. Bilberry (Vaccinium sp.) helps maintain collagen balance and prevents the breakdown of vitamin C. Many people with glaucoma have been shown to have deficiencies of chromium and zinc. Supplementation with these two minerals may, therefore, deter the onset or progression of the disease. Alpha lipoic acid and other antioxidants may improve visual functioning.
A naturopathic approach called contrast hydrotherapy can be used to stimulate circulation in the eyes.
Compresses can be applied over the eyes, alternating three minutes with hot water and one minute with cold water, always ending with the cold. Biofeedback can be used to reduce the pressure in the eyes by increasing relaxation. Meditation, stress reduction, t'ai chi, yoga, exercise, and acupuncture also may lower IOP. Remedies used to lower IOP must be taken continually to avoid optic nerve damage. In addition to other treatments, a glaucoma patient should always remain under the care of an ophthalmologist or optometrist who is licensed to treat glaucoma, so that IOP and optic nerve damage can be monitored.
The objective of glaucoma treatment is usually to decrease IOP. When glaucoma is diagnosed, drugs, typically given as eye drops, are usually tried before surgery. Several classes of medications are effective at lowering IOP and thus, at preventing optic nerve damage in chronic and neonatal glaucoma. These inlcude beta-blockers, such as Timoptic, and carbonic anhydrase inhibitors, such as acetazolamide. Alpha-2 agonists, such as Alphagan, inhibit the production of aqueous humor. Miotics, such as pilocarpine, and prostaglandin analogues, like Xalatan, increase the drainage of aqueous humor. Different medications lower IOP different amounts, and a combination of medications may be necessary. Attacks of acute closed-angle glaucoma are medical emergencies. In such cases, IOP is rapidly lowered by use of acetazolamide, hyperosmotic agents, a topical beta-blocker, and pilocarpine. All of these drugs have side effects, some of which are rare, but serious and potentially life threatening. Patients taking them should be monitored closely, especially for cardiovascular, pulmonary, and behavioral symptoms. IOP should also be monitored and measured three to four times per year.
Laser peripheral iridiotomy or other microsurgery is used to open the drainage canals or to make an opening in the iris to increase the outflow of aqueous humor. These surgeries are usually successful, but effects often last less than a year. Nevertheless, they are an effective treatment for patients whose IOP is not sufficiently lowered by drugs or for those who cannot tolerate the drugs. Surgery is usually used in cases of congenital glaucoma, since the medications are often too harsh for children. Youngsters often respond to surgery better than adults, and have an excellent chance for preserving lifelong good vision.
If glaucoma is left untreated, optic nerve damage will result in a progressive loss of vision. Once blindness develops due to glaucoma, it cannot be reversed. With early treatment and monitoring, however, serious vision loss can usually be prevented.
While glaucoma is not preventable, early detection and treatment can help to prevent serious damage to vision. Those with risk factors should have regular eye exams and avoid medicines that tend to be implicated in the development of glaucoma, including some over-thecounter cold and allergy medications. All medications should be checked for their ingredients. Alternatives for drugs that aggravate glaucoma should be discussed with a healthcare provider.
The Editors of Time-Life Books. The Medical Advisor: The Complete Guide to Alternative and Conventional Treatments. Alexandria, VA: Time-Life, Inc., 1996.
Epstein, David L., R. Rand Allingham, and Joel S. Schuman. Chandler and Grant's Glaucoma. 4th ed. Baltimore: Williams & Wilkins, 1997.
Marks, Edith and Rita Montauredes. Coping with Glaucoma. New York: Avery, 1997.
American Academy of Ophthalmology. P.O. Box 7424, San Francisco, CA 94120-7424. <http://www.eyenet.org/aao_index.html>.
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