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Cataracts

Cataracts

Definition

A cataract is a cloudiness or opacity in the normally transparent crystalline lens of the eye. This cloudiness can cause a decrease in vision and may lead to eventual blindness.

Description

The human eye has several parts. The outer layer of the eyeball consists of a transparent dome-shaped cornea and an opaque, white sclera. The cornea and sclera help protect the eye. The next layer includes the iris, pupil, and ciliary body. The iris is the colored part of the eye and the pupil is the small dark round hole in the middle of the iris. The pupil and iris allow light into the eye. The ciliary body contains muscles that help in the eye's focusing ability. The lens lies behind the pupil and iris. It is covered by a cellophane-like capsule. The lens is normally transparent, elliptical in shape, and somewhat elastic. This elasticity allows the lens to focus on both near and far objects. The lens is attached to the ciliary body by fibers (zonules of Zinn). Muscles in the ciliary body act on the zonules, which then change the shape of the lens. This process is called accommodationthe lens focuses images to help make vision clear. As people age, the lens hardens and changes shape less easily. As a result, the accommodation process becomes more difficult, making it harder to see things up close. This generally occurs around the age of 40 and continues until about age 65. The condition is called presbyopia. It is a normal condition of aging, generally resulting in the need for reading glasses.

The lens is made up of approximately 35% protein and 65% water. As people age, degenerative changes in the lens's proteins occur. Changes in the proteins, water content, enzymes, and other chemicals are some of the reasons for the formation of a cataract.

The major areas of the lens are the nucleus, the cortex, and the capsule. The nucleus is in the center of the lens, the cortex surrounds the nucleus, and the capsule is the outer layer. Opacities can occur in any area of the lens. Cataracts, then, can be classified according to location (nuclear, cortical, or posterior subcapular cataracts). The density and location of the cataract determine the amount of vision affected. If the cataract forms in the area of the lens directly behind the pupil, vision may be significantly impaired. A cataract that occurs on the outer edges or side of the lens will create less of a visual problem.

Cataracts in the elderly are so common that they are thought to be a normal part of the aging process. Between the ages of 52 and 64, there is a 50% chance of having a cataract, while at least 70% of those 70 and older are affected. In 2004, it was revealed that blacks are twice as likely to develop cataracts as whites. Cataracts associated with aging (senile or age-related cataracts) most often occur in both eyes, with each cataract progressing at a different rate. Initially, cataracts may not affect vision. If the cataract remains small or at the periphery of the lens, the visual changes may be minor.

Cataracts that occur in people other than the elderly are much less common. Congenital cataracts occur very rarely in newborns. Genetic defects or an infection or disease in the mother during pregnancy are among the causes of congenital cataracts. Traumatic cataracts may develop after a foreign body or trauma injures the lens or eye. Systemic illnesses, such as diabetes, may result in cataracts. Cataracts can also occur secondary to other eye diseasesfor example, an inflammation of the inner layer of the eye (uveitis ) or glaucoma. Such cataracts are called complicated cataracts. Toxic cataracts result from chemical toxicity, such as steroid use. Cataracts can also result from exposure to the sun's ultraviolet (UV) rays.

Causes and symptoms

Recent studies have been conducted to try to determine whether diet or the use of vitamins might have an effect on the formation of cataracts in older people. The results have been mixed, with some studies finding a connection and other studies finding none. Much interest has been focused on the use of antioxidant supplements as a protection against cataracts. Antioxidant vitamins such as vitamins A, C, E and beta-carotene help the body clean-up oxygen-free radicals. Some vitamins are marketed specifically for the eyes. Patients should speak to their doctors about the use of such vitamins.

Smoking and alcohol intake have been implicated in cataract formation. Some studies have determined that a diet high in fat will increase the likelihood of cataract formation, while an increase in foods rich in antioxidants will reduce the incidence. More research is needed to determine if diet, smoking, alcohol consumption, or vitamins have any connection to the formation of cataracts.

There are several common symptoms of cataracts:

  • gradual, painless onset of blurry, filmy, or fuzzy vision
  • poor central vision
  • frequent changes in eyeglass prescription
  • changes in color vision
  • increased glare from lights, especially oncoming headlights when driving at night
  • "second sight" improvement in near vision (no longer needing reading glasses), but a decrease in distance vision
  • poor vision in sunlight
  • presence of a milky whiteness in the pupil as the cataract progresses.

Diagnosis

Both ophthalmologists and optometrists may detect and monitor cataract growth and prescribe prescription lenses for visual deficits. However, only an ophthalmologist can perform cataract extraction.

Cataracts are easily diagnosed from the reporting of symptoms, a visual acuity exam using an eye chart, and by examination of the eye itself. Shining a penlight into the pupil may reveal opacities or a color change of the lens even before visual symptoms have developed. An instrument called a slit lamp is basically a large microscope. This lets the doctor examine the front of the eye and the lens. The slit lamp helps the doctor determine the location of the cataract.

Some other diagnostic tests may be used to determine if cataracts are present or how well the patient may potentially see after surgery. These include a glare test, potential vision test, and contrast sensitivity test.

Treatment

For cataracts that cause no symptoms or only minor visual changes, no treatment may be necessary. Continued monitoring and assessment of the cataract is needed by an ophthalmologist or optometrist at scheduled office visits. Increased strength in prescription eyeglasses or contact lenses may be helpful. This may be all that is required if the cataract does not reduce the patient's quality of life.

Cataract surgerythe only option for patients whose cataracts interfere with vision to the extent of affecting their daily livesis the most frequently performed surgery in the United States. It generally improves vision in over 90% of patients. Some people have heard that a cataract should be "ripe" before being removed. A cataract is considered ripe or mature when the lens is completely opaque. Most cataracts are removed before they reach this stage. Sometimes cataracts need to be removed so that the doctor can examine the back of the eye more carefully. This is important in patients with diseases that may affect the eye. If cataracts are present in both eyes, only one eye at a time should be operated on. Healing occurs in the first eye before the second cataract is removed, sometimes as early as the following week. A final eyeglass prescription is usually given about four to six weeks after surgery. Patients will still need reading glasses. The overall health of the patient needs to be considered in making the decision to operate. However, age alone need not preclude effective surgical treatment of cataracts. People in their nineties can have successful return of vision after cataract surgery.

Surgery to remove cataracts is generally an outpatient procedure. A local anesthetic is used and the procedure lasts about one hour. Removal of the cloudy lens can be done by several different procedures. The three types of cataract surgery available are:

  • Extracapsular cataract extraction. This type of cataract extraction is the most common. The lens and the front portion of the capsule are removed. The back part of the capsule remains, providing strength to the eye.
  • Intracapsular cataract extraction. The lens and the entire capsule are removed. This method carries an increased risk for detachment of the retina and swelling after surgery. It is rarely used.
  • Phacoemulsification. This type of extracapsular extraction needs a very small incision, resulting in faster healing. Ultrasonic vibration is applied to the lens to break it up into very small pieces which are then aspirated out of the eye with suction by the ophthalmologist. A new liquid technique that its inventor says may one day replace ultrasound has been invented, but has not yet been proven in clinical trials.

A replacement lens is usually inserted at the time of the surgery. A plastic artificial lens called an intraocular lens (IOL) is placed in the remaining posterior lens capsule of the eye. When the intracapsular extraction method is used, an IOL may be clipped onto the iris. Contact lenses and cataract glasses (aphakic lenses) are prescribed if an IOL was not inserted. A folding IOL is used when phacoemulsification is performed to accommodate the small incision.

Antibiotic drops to prevent infection and steroids to reduce inflammation are prescribed after surgery. An eye shield or glasses during the day will protect the eye from injury while it heals. During the night, an eye shield is worn. The patient returns to the doctor the day after surgery for assessment, with several follow-up visits over the next two months to monitor the healing process.

Prognosis

The success rate of cataract extraction is very high, with a good prognosis. A visual acuity of 20/40 or better may be achieved. If an extracapsular cataract extraction was performed, a secondary cataract may develop in the remaining back portion of the capsule. This can occur one to two years after surgery. YAG capsulotomy is most often used for this type of cataract. YAG stands for yttrium aluminum garnet, the name of the laser used for this procedure. This is a painless outpatient procedure and requires no incision. The laser beam makes a small opening in the remaining back part of the capsule, allowing light through.

In a very small percentage (3-5%) of surgical cataract extractions, complications occur. Infections, swelling of the cornea (edema ), bleeding, retinal detachment, and the onset of glaucoma have been reported. Some problems may occur one to two days, or even several weeks, after surgery. Any haziness, redness, decrease in vision, nausea, or pain should be reported to the surgeon immediately.

Prevention

Preventive measures emphasize protecting the eyes from UV radiation by wearing glasses with a special coating to protect against UV rays. Dark lenses alone are not sufficient. The lenses must protect against UV light (specifically, UV-A and UV-B). Antioxidants may also provide some protection by reducing free radicals that can damage lens proteins. A healthy diet rich in sources of antioxidants, including citrus fruits, sweet potatoes, carrots, green leafy vegetables, and/or vitamin supplements may be helpful. In 2004, research in England revealed that nonsteroidal anti-inflammatory drugs (over-the counter pain killers such as aspirin ) may help decrease risk of cataracts by as much as 43%. When taking certain medications, such as steroids, more frequent eye exams may be necessary. Patients should speak to their doctors to see if medications may affect their eyes.

Resources

PERIODICALS

"Blacks May Have Higher Incidence of Cataract." Review of Optometry April 15, 2004: 12.

"Research Suggests Aspirin Helps Combat Cataracts." Health & Medicine Week June 21, 2004: 724.

Talsma, Julia. "Liquefication Device Provides Safe Removal of All Cataracts: Lens Emulsified with BSS Micropulses Using Reusable Titanium Handpiece With Smooth Polymer Tip." Ophthlamology Times June 1, 2004: 50.

ORGANIZATIONS

American Academy of Ophthalmology. 655 Beach Street, P.O. Box 7424, San Francisco, CA 94120-7424. http://www.eyenet.org.

American Optometric Association. 243 North Lindbergh Blvd., St. Louis, MO 63141. (314) 991-4100. http://www.aoanet.org.

The Lighthouse. 111 East 59th St., New York, NY 10022. (800) 334-5497. http://www.lighthouse.org.

Prevent Blindness America. 500 East Remington Road, Schaumburg, IL 60173. (800) 331-2020. http://www.preventblindness.org.

KEY TERMS

Aphakia Absence of the lens of the eye.

Ciliary body A structure in the eye that contains muscles that will affect the focusing of the lens.

Glaucoma Disease of the eye characterized by increased pressure of the fluid inside the eye. Untreated, glaucoma can lead to blindness.

Phacoemulsification Surgical procedure to remove a cataract using sound waves to disintegrate the lens which is then removed by suction.

Retina The innermost layer of the eyeball. Images focused onto the retina are then sent to the brain.

Ultraviolet radiation (UV) Invisible light rays that may be responsible for sunburns, skin cancers, and cataract formation.

Uveitis Inflammation of the uvea. The uvea is a continuous layer of tissue that consists of the iris, the ciliary body, and the choroid. The uvea lies between the retina and sclera.

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Cataracts

Cataracts

Definition

A cataract is a cloudiness or opacity in the normally transparent crystalline lens of the eye. This cloudiness can cause loss of vision and may lead to eventual blindness.

Description

The human eye has several parts. The outer layer of the eyeball consists of a transparent dome-shaped cornea and an opaque white sclera, which is a fibrous membrane. The cornea and sclera help protect the eye. The next layer includes the iris, pupil, and ciliary body. The iris is the colored part of the eye; the pupil is the small dark round hole in the middle of the iris. The pupil and iris allow light into the eye. The ciliary body contains muscles that help the eye to focus. The lens lies behind the pupil and iris. It is covered by a cellophane-like capsule. The lens is normally transparent, elliptical in shape, and somewhat elastic. This elasticity allows the lens to focus on both near and far objects. The lens is attached to the ciliary body by fibers (zonules of Zinn). Muscles in the ciliary body act on the zonules, which then change the shape of the lens. This changing of shape is called accommodation. As people age, the lens hardens and accommodates less easily, which makes it harder for the person to see close objects. This hardening of the lens generally occurs around the age of 40 and continues until about age 65. The condition is called presbyopia. It is a normal condition of aging , generally resulting in the need for reading glasses.

The lens is made up of approximately 35% protein and 65% water. As people age, the proteins in the lens begin to degenerate. Changes in the proteins, water content, enzymes, and other chemicals are some of the causes of cataract formation.

The major parts of the lens are the nucleus, the cortex, and the capsule. The nucleus is in the center of the lens, the cortex surrounds the nucleus, and the capsule is the outer layer. Opaque areas can develop in any part of the lens. Cataracts, then, can be classified according to location (nuclear, cortical, or posterior subcapular cataracts). The density and location of the cataract determines the extent of vision affected. If the cataract forms in the area of the lens directly behind the pupil, the person's vision may be significantly impaired. A cataract that occurs on the outer edges or side of the lens will cause less severe impairment.

Cataracts in the elderly are so common that they are considered a normal part of the aging process. People between the ages of 5264 have a 50% chance of developing a cataract, while at least 70% of those 70 and older are affected. Cataracts associated with aging (senile or age-related cataracts) most often occur in both eyes, with each cataract progressing at a different rate. At first, these cataracts may not affect vision. If the cataract remains small or at the periphery of the lens, the visual changes may be minor.

Cataracts that occur in people other than the elderly are much less common. Congenital cataracts occur very rarely in newborns. Genetic defects or an infection or disease in the mother during pregnancy are among the causes of congenital cataracts. There is a condition called blue cataracts, which is inheritance-linked and affects primarily Tibetans and some other Asians. Traumatic cataracts may develop after an injury or foreign body damages the lens or eye. Systemic illnesses like diabetes may result in cataracts. Cataracts can also occur secondary to other eye diseasesfor example, an inflammation of the inner layer of the eye (uveitis) or glaucoma . Such cataracts are called complicated cataracts. Toxic cataracts result from chemical toxicity, such as steroid use. Cataracts can also result from exposure to the sun's ultraviolet (UV) rays.

Causes & symptoms

Recent studies have been conducted to determine whether diet or the use of vitamins might have an effect on the formation of cataracts in older people. Although debate continues, several studies reported in late 2001 that a diet rich in certain caretenoids may protect against development of cataracts. Likewise, there has been considerable interest in the use of antioxidant supplements as a protection against cataracts. Such antioxidant vitamins as vitamins A, C, E, and beta-carotene protect body tissues against free radicals, which are byproducts of oxidation. Vitamin C in particular, has shown the strongest impact on lower rates of cataracts. Some vitamins are marketed specifically for the eyes. Patients should speak to their doctors about the use of such vitamins.

Studies also have recently linked changes in lens proteins to cataract formation. Soluble proteins in the lens begin to condense and form clumps, leading to cataracts. Researchers have identified mutations in genes that likely lead to protein changes resulting in juvenile cataracts. The next step is to study a possible genetic relationship to formation of age-related cataracts as well.

Smoking and alcohol intake have been implicated in cataract formation. Some studies have determined that a diet high in fat will increase the likelihood of cataract formation, while eating more foods rich in antioxidants will lower the risk. More research is needed to determine if diet, smoking, alcohol consumption, or vitamins have any connection to the formation of cataracts.

Cataracts may have the following symptoms:

  • gradual, painless onset of blurry, filmy, or fuzzy vision
  • poor central vision
  • frequent changes in eyeglass prescription
  • changes in color vision
  • increased glare from lights, especially oncoming headlights when driving at night
  • "second sight" improvement in near vision (no longer needing reading glasses), but a decrease in distance vision
  • spoor vision in sunlight
  • the presence of a milky whiteness in the pupil as the cataract progresses

Diagnosis

Both ophthalmologists and optometrists may detect and monitor cataract growth and prescribe prescription lenses for visual deficits. Only an ophthalmologist, however, can perform cataract extraction.

Cataracts are easily diagnosed from the reporting of symptoms, a visual acuity examination using an eye chart, and by a physician or optometrist's examination of the eye. Shining a penlight into the pupil may reveal opacities or a color change of the lens even before the patient develops visual symptoms. A slit lamp, which is basically a large microscope, allows the doctor to examine the front of the eye and the lens, and to determine the location of the cataract.

Some other diagnostic tests may be used to determine if cataracts are present or how much improvement the patient may have after surgery. These tests include a glare test, potential vision test, and contrast sensitivity test.

Treatment

Because free radicals have been implicated as a cause of cataracts, alternative therapies emphasize the importance of a healthful diet, nutritional supplements and/or herbal remedies to prevent and slow down the progression of cataracts.

Nutritional therapy

A naturopathic doctor or a nutritionist may recommend the following dietary changes:

  • Reduce consumption of salty or fatty foods. Diabetics should also limit their intake of milk and other dairy products.
  • Increase intake of foods that are high in beta-carotene: peaches, apricots, berries, carrots, and leafy green vegetables. Beta-carotene and other antioxidants can protect against or slow down the development of cataracts.
  • Stop cigarette smoking and avoid exposure to secondhand smoke.
  • Eat a diet rich in fruits and vegetables with high concentrations of vitamin C. Take supplemental vitamin C (1 g three times daily) and vitamin A (25,000 IU per day).
  • Take supplemental beta-carotene (25,000100,000 IU per day) and selenium (400 mcg per day). Low selenium levels may increase the risk of cataracts.
  • Increase intake of L-cysteine (400 mg per day), L-glutamine (200 mg per day), and L-glycine (200 mg per day). These three amino acids may be beneficial to some cataract patients.
  • Add other supplements: zinc, lutein, riboflavin , and cod liver oil.

Herbal therapy

There are two herbal remedies that may help protect the eyes against cataracts:

  • Bilberries (4080 mg daily). Early research indicates that eating bilberries may halt cataract progression.
  • Hachimijiogan. Hachimijiogan is an ancient Chinese herbal formula. Animal studies suggest that it may protect the eyes against cataracts by increasing the glutathione content of the lens.

Allopathic treatment

Cataracts that cause no symptoms or only minor visual changes may not require any treatment. An ophthalmologist or optometrist should continue to monitor and assess the cataract at scheduled office visits. Stronger prescription eyeglasses or contact lenses may be helpful.

Cataract surgery is the only option for patients whose cataracts interfere with vision to the extent of affecting their daily lives. It is the most frequently performed surgery in the United States. It generally improves vision in over 90% of patients. Some people have heard that a cataract should be "ripe" before being removed. A "ripe" or mature cataract means that the lens is completely opaque. Most cataracts are removed before they reach that stage. Sometimes cataracts need to be removed so that the doctor can examine the back of the eye more carefully. Patients with diseases that may affect the eye may require cataract surgery for this reason. If cataracts are present in both eyes, only one eye at a time should be operated on. Healing occurs in the first eye before the second cataract is removed, sometimes as early as the following week. A final eyeglass prescription is usually given about four to six weeks after surgery. Patients will still need reading glasses. The overall health of the patient needs to be considered in making the decision to operate. Age alone, however, need not preclude effective surgical treatment of cataracts; people in their 90s can benefit from cataract surgery.

Patients are given antibiotic drops to prevent infection and steroids to reduce inflammation after surgery. An eye shield or glasses during the day will protect the eye from injury while it heals. At night, the patient should wear an eye shield. The patient returns to the doctor the day after surgery for assessment, with several follow-up visits over the next two months to monitor the healing process.

Expected results

The success rate of cataract extraction is very high, with a good prognosis. Visual acuity of 20/40 or better may be achieved. If an extracapsular cataract extraction was performed, a secondary cataract may develop in the remaining back portion of the capsule one to two years after surgery. YAG capsulotomy is most often used to treat this type of cataract. YAG stands for yttrium aluminum garnet, the name of the laser used for this procedure. The laser beam makes a small opening in the remaining back part of the capsule, allowing light through.

Complications occur in a very small percentage (35%) of surgical cataract extractions. Infections , swelling of the cornea (edema ), bleeding, retinal detachment , and the onset of glaucoma have been reported. Any haziness, redness, decrease in vision, nausea , or pain should be reported to the surgeon immediately.

Prevention

Preventive measures emphasize protecting the eyes from UV radiation by wearing glasses with a special coating to protect against UV rays. Dark lenses alone are not sufficient. The lenses must protect against UV light (specifically, UV-A and UV-B). Antioxidants and herbal remedies may also provide some protection by reducing free radicals that can damage lens proteins. A healthful diet rich in sources of antioxidants, including citrus fruits, sweet potatoes, carrots, green leafy vegetables, and/or vitamin supplements may be helpful. When taking certain medications, such as steroids, more frequent eye exams may be necessary. Patients should speak to their doctors to see if medications may affect their eyes.

Resources

BOOKS

"Cataract." Medical-Surgical Nursing: Concepts and Clinical Practice, fifth edition. Edited by Wilma J. Phipps et al. St. Louis, MO: Mosby-Year Book, Inc., 1995.

Liberman, Shari, and Nancy Bruning. The Real Vitamin & Mineral Book: Using Supplements for Optimal Health,, 2nd ed. Garden City Park, NY: Avery Publishing Group, 1997.

Murray, Michael, and Joseph Pizzorno. Encyclopedia of Natural Medicine. Revised second ed. Rocklin, CA: Prima Health, 1997.

PERIODICALS

Friedrich, MJ. "Insight Into Opacity: Clues to Cataract Formation." JAMA, The Journal of the American Medical Association 286 no. 14 (October 10, 2001): 1705.

"Nutrients May Prevent Age-Related Eye Diseases." Health and Medicine Week (November 26,2001): 2.

ORGANIZATIONS

American Academy of Ophthalmology (National Eyecare Project). P.O. Box 429098. San Francisco, CA 94142-9098. (800) 222-EYES. http://www.eyenet.org.

American Optometric Association. 243 North Lindbergh Blvd. St. Louis, MO 63141. (314) 991-4100. http://www.aoanet.org.

The Lighthouse. 111 East 59th Street. New York, NY 10022. (800) 334-5497. http://www.lighthouse.org.

Prevent Blindness America. 500 East Remington Road. Schaumburg, IL 60173. (800) 331-2020. http://www.prevent-blindness.org.

Teresa G. Odle

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Cataracts

CATARACTS

DEFINITION


A cataract is a cloudiness in the lens of the eye, which is normally clear and transparent. The cloudiness caused by a cataract may eventually lead to decreased vision and blindness.

DESCRIPTION


The lens is positioned near the front of the eyeball. It is protected by the cornea, which covers the front of the eyeball. The purpose of the lens is to focus the light waves that enter the eye. Muscles around the lens can change the shape of the lens. In this way, objects both close at hand and far away can be brought into focus.

The lens is made up of about 35 percent protein and 65 percent water. Proteins are chemical compounds found in all cells. As people grow older, the chemicals present in their eyes may change. Proteins may break down, water may seep out of the eye, or other changes may occur. One consequence of such changes is the formation of cataracts.

Cataracts are common in older people. They are so common that they are regarded as a normal part of the aging process. For those between the ages of 50 and 65, the chance of having a cataract is about 50 percent. Beyond the age of 70, the risk rises to about 70 percent.

Cataracts: Words to Know

Cornea:
The transparent outer coating on the front of the eyeball.
Lens:
A transparent oval body located near the front of the eye that focuses light waves.
Proteins:
Chemicals that are found in every cell in the human body and carry out many essential functions.
Retina:
A thin layer of tissue at the back of the eyeball on which light waves are focused and then transmitted to the brain by way of the optic nerve.
Steroids:
Naturally occurring chemicals that help reduce inflammation, pain, and swelling.

Cataracts also occur in young people, but are much less common. For example, the lens may be injured by some foreign object, which may lead to the formation of a cataract. Cataracts are also caused by certain diseases, such as diabetes mellitus (see diabetes mellitus entry).

Cataracts generally have little or no effect on vision in their early stages. As they develop, they can lead to vision problems and, eventually, blindness may result.

CAUSES


The vast majority of cataracts are thought to have no specific cause. They simply develop as a person grows older. Researchers are exploring a number of theories about possible causes of cataracts. These theories suggest that smoking, alcohol, and high-fat diets may increase a person's risk for cataracts. They also suggest that vitamin supplements may decrease the risk for cataracts.

SYMPTOMS


The most common symptom of cataracts is a gradual, painless change in one's vision. Objects become more blurry, filmy, or fuzzy to a person with cataracts. Some other common symptoms of cataracts include the following:

  • Frequent changes in eyeglass prescription
  • Changes in color vision
  • Increased difficulty in seeing at night
  • Poor vision in sunlight
  • Presence of a milky white film in the pupil of the eye

DIAGNOSIS


Cataracts are easily diagnosed by any eye specialist. They can often be detected before a patient is aware of vision problems. The most direct diagnosis is made by shining a light into the patient's eyes. Color changes or cloudiness are often visible if a cataract is developing.

TREATMENT


No treatment is needed for mild cases of cataracts. If they do not interfere with a patient's vision, they are not treated. If moderate vision problems develop, a stronger eyeglass prescription may be all that is needed.

In more serious cataract cases, surgery may be necessary. Surgery is the only procedure available for treating advanced cases of cataracts. Cataract surgery is relatively simple. By the late 1990s, it was the most frequently performed surgery in the United States.

Cataract surgery can be performed in a doctor's office and usually lasts about an hour. The cloudy lens is removed. An artificial plastic lens is then inserted into the space formerly occupied by the damaged lens. The patient is given antibiotics and steroids after the surgery. The antibiotics protect against infection by bacteria. The steroids help reduce the pain and inflammation caused by the surgery.

PROGNOSIS


Many cases of cataracts never require treatment other than a change in one's eyeglass prescription. If surgery is required, the success rate is very high. More than 90 percent of patients experience improved vision. Complications occur in a very small fraction (3 to 5 percent) of cataract surgeries. These complications include infections, swelling of the cornea, bleeding, and damage to the retina.

PREVENTION


Since most cases of cataracts are part of the natural aging process, there is not much that can be done to prevent their development. Wearing dark glasses in direct sunlight may be helpful. Radiation from the sun is thought to be one possible cause of changes in proteins in the lens. A healthy diet rich in citrus fruits, sweet potatoes, carrots, and green leafy vegetables, and supplemented by vitamins, may also be helpful in delaying the onset of cataracts.

FOR MORE INFORMATION


Books

Salmans, Sandra. Your Eyes: Questions You Have Answers You Need. Allentown: People's Medical Society, 1996.

Shulman, Julius. Cataractsfrom Diagnosis to Recovery: The Complete Guide for Patients and Families. New York: St. Martin's Press, 1995.

Organizations

American Academy of Ophthalmology (National Eyecare Project). PO Box 7424, San Francisco, CA 941207424. (800) 222EYES. http://www.eyenet.org.

American Optometric Association. 243 North Lindbergh Boulevard, St. Louis, MO, 63141. (314) 9914100. http://www.aoanet.org.

Lighthouse International. 111 East 59th Street, New York, NY 10022. (800) 8290500. http://www.lighthouse.org.

Prevent Blindness America. 500 East Remington Road, Schaumburg, IL 60173. (800) 3312020. http://www.prevent-blindness.org.

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Cataracts

Cataracts

What Happens When People Get Cataracts?

How Do Doctors Diagnose and Treat Cataracts?

Can Cataracts Be Prevented?

Resources

Cataracts develop when the lens of the eye becomes cloudy. They usually impair vision and sometimes occur as people get older.

KEYWORDS

for searching the Internet and other reference sources

Ophthalmology

Vision

Many people who live to an old age will develop cataracts, often without noticing the effects until they are past age 70. For some, it might mean only a slight change in vision. Others, however, will find they need surgery to remove the cloudy lens.

A cataract results when the clear lens in the eye becomes cloudy. Like frost on a window, the cataract makes it more difficult to see clearly. The reason is that the light passing through the cloudy lens is distorted before it reaches the visual receptors in the retina* at the inside rear of the eyeball.

* retina
lines the inner surface of the back of the eyeball. It contains millions of light-sensitive cells that change light into nerve signals that the brain can interpret.

What Happens When People Get Cataracts?

Researchers believe that cataracts develop because the proteins in the eye change as people age. The changes cause the lens to become cloudy. Other factors, such as smoking, poor nutrition, eye injury, exposure to excessive sunlight, and certain medical conditions such as diabetes, also may be factors that put people at higher risk of developing cataracts.

Cataracts develop slowly. At first, people notice difficulty reading the newspaper, or they experience blurry vision. The eyes become more sensitive to light, and seeing at night becomes especially difficult. People with cataracts often say they feel they have a film over their eyes, as if they are looking through a piece of gauze.

For a short time, the condition actually may benefit some people who always had trouble seeing things that are near them, such as the words on this page. The cloudiness of a cataract changes how light is focused and temporarily results in better vision for such people. They may find themselves able to read for the first time without eyeglasses, a condition sometimes called second sight. As the cataracts worsen, however, eventually these people will experience increasing visual difficulties.

How Do Doctors Diagnose and Treat Cataracts?

An ophthalmologists* eye exam can detect a cataract and follow its progress. When cataracts are detected, the doctor can evaluate the symptoms and decide on the best course of treatment.

* ophthalmologist
is a medical doctor who specializes in treating diseases of the eye.

Many people can live with the condition untreated. For others, surgery may be recommended to remove the cloudy lens and to replace it with a clear artificial lens that is smaller in size than a dime. Cataract surgery improves vision in 90 to 95 percent of the people who have it. It is one of the most common operations, with more than 1 million performed each year. Surgery generally is done when the lens has become so opaque or cloudy that reading, driving, or watching television become major problems.

Can Cataracts Be Prevented?

Some studies suggest that vitamins C and E may lower the likelihood of developing cataracts. That is because these vitamins appear to reduce damage to the proteins that are linked to the development of cataracts. Also, using sunglasses that block ultraviolet light may lower a persons risk of developing cataracts, because studies strongly suggest that sunlight plays a role in their development. Avoiding cataracts is another important reason to avoid smoking, as smokers appear to have an increased risk of developing cataracts.

See also

Presbyopia

Resources

Book

Cassel, Gary H., M.D., Michael D. Billig, O.D., and Harry G. Randall, M.D. The Eye Book: A Complete Guide to Eye Disorders and Health. Baltimore: Johns Hopkins University Press, 1998. A good general reference on eye problems.

Organization

The U.S. National Eye Institute posts a fact sheet about cataracts at its website. http://www.nei.nih.gov/TextSite/publications/cataract.htm

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Cataracts

Cataracts

Definition

The lens of the eye is normally transparent. A cataract is a condition in which the lens of the eye becomes cloudy or opaque. This cloudiness can impair vision and may lead to eventual blindness.

Description

The human eye has several parts. The outer layer of the eyeball consists of a transparent dome-shaped cornea and an opaque, white sclera. The cornea and sclera help protect the eye. The next layer includes the iris, pupil, and ciliary body. The iris is the colored part of the eye and the pupil is the small, dark, round hole in the center of the iris. The pupil is primarily responsible for allowing light into the eye. The ciliary body contains muscles that help the eye focus. The lens, which lies behind the pupil and iris, is covered by a cellophane-like capsule. It is normally transparent, elliptical in shape, and somewhat elastic. Due to this elasticity, the lens can focus on both near and far objects. The lens is attached to the ciliary body by fibers (zonules of Zinn). Muscles in the ciliary body act on the zonules, which then change the shape of the lens. This process is called accommodation—the lens focuses images to help make vision clear. As people age, the lens hardens and changes shape less easily. As a result, accommodation becomes more difficult, making it harder to see things up close. This normal aging condition, called presbyopia, generally occurs around age 40 and continues until about age 65. Individuals with this condition generally need reading glasses.

The lens is made up of approximately 35% protein and 65% water. As people age, degenerative changes in the lenses' proteins occur. Changes in the proteins, water content, enzymes, and other chemicals are some of the reasons for the formation of a cataract.

The major areas of the lens are the nucleus, the cortex, and the capsule. The nucleus is in the center of the lens, the cortex surrounds the nucleus, and the capsule is the outer layer. Opacities can occur in any area of the lens, and cataracts can be classified according to their location (nuclear, cortical, or posterior subcapular cataracts). The density and location of the cataract determines the amount of vision affected. If the cataract forms in the area of the lens directly behind the pupil, vision may be significantly impaired. A cataract that occurs on the outer edges or side of the lens causes less visual impairment.

Cataracts in the elderly are so common that they are thought to be a normal part of aging. Cataracts affect about 50% of individuals between the ages of 52-64, while at least 70% of those 70 and older are affected. Cataracts associated with aging (senile or age-related cataracts) are usually bilateral (occur in both eyes) with asymmetric progression (different rates of progression). Initially, cataracts may not affect vision. If the cataract remains small or at the periphery of the lens, the visual changes may be minor.

Cataracts are much less common in younger people. Congenital cataracts are rare in newborns. When they do occur, they may be due to genetic defects or an infection or disease in the mother during pregnancy. Traumatic cataracts may develop after a foreign body or trauma injures the lens or the eye. Systemic illnesses, such as diabetes, also may result in cataracts. Cataracts can occur secondary to other eye diseases—for example, uveitis or glaucoma. Such cataracts are called complicated cataracts. Toxic cataracts result from chemical toxicity, such as steroid use. Cataracts also can result from exposure to the sun's ultraviolet (UV) rays.

Causes and symptoms

Recent studies have investigated the effect of nutrition on cataract formation. The results have been mixed, with some studies finding that there is a connection between nutrition and cataract formation and other studies finding none. Much interest has been focused on the use of antioxidant supplements as a protection against cataracts. Antioxidants, such as vitamins A, C, E, and beta-carotene, help the body neutralize oxygen-free radicals.

Smoking and alcohol intake, however, have been implicated in cataract formation, as have the use of oral corticosteriods and antihypertensive agents. Some studies have determined that a diet high in fat increases the likelihood of cataract formation, while an increase in foods rich in antioxidants reduces the incidence. More research is needed to determine the precise role played by diet, smoking, alcohol consumption, and antioxidants in the formation of cataracts.

Some unrelated physical conditions, such as diabetes mellitus, also may contribute to cataracts. Eye injuries and sun exposure also are causative factors.

There are several common symptoms of cataracts:

  • gradual, painless onset of blurry, filmy, or fuzzy vision
  • poor central vision
  • frequent changes in eyeglass prescriptions
  • changes in color vision
  • increased glare from lights, especially oncoming headlights when driving at night
  • "second sight" improvement in near vision (no longer needing reading glasses)
  • poor vision in sunlight
  • presence of a milky whiteness in the pupil as the cataract progresses

Diagnosis

Ophthalmologists and optometrists detect and monitor cataract growth and prescribe prescription lenses for visual deficits. Ophthalmologists perform cataract extraction.

Cataract diagnosis begins with a complete eye exam. The ophthalmic assistant, technician, or nurse gathers information to determine the progression of the vision loss. It is unusual for cataracts to cause rapid vision loss, but sometimes patients believe the vision problem is acute because vision in the better eye has only recently been compromised. Patient history includes a review of refractive history, previous ocular disease, amblyopia, eye surgery, and trauma. Ophthalmic personnel also question patients about difficulties driving, reading, and performing daily activities, and record any medication the patient currently uses.

The ocular exam determines the severity of the cataract and assesses other factors that might contribute to the potential for good vision after surgery. The exam includes measurement of visual acuity under both low and high illumination, biomicroscopy with pupillary dilation, stereoscopic fundus examination with pupillary dilation, assessment of ocular motility and binocularity, visual fields, evaluation of pupillary responses, refraction, and measurement of intraocular pressure (IOP).

Treatment

No treatment may be necessary for cataracts that cause no symptoms or that cause only minor visual changes. It is important for an ophthalmologist or optometrist to continue to monitor and assess the cataract during regular office visits. Increased strength in prescription eyeglasses or contact lenses may be diagnostic and beneficial.

Cataract surgery—the only option for patients whose cataracts interfere with vision to the extent that their daily activities are affected—is the most frequently performed surgery in the United States. It generally improves vision in more than 90% of patients. Most cataracts are removed before the lens is completely opaque or mature. This is done to minimize the impact of the cataract on the patient's daily life and also to decrease the risk of other eye complications. Sometimes cataracts need to be removed so the surgeon can examine the back of the eye more carefully. This is important in patients with diseases that may affect the eye. If cataracts are present in both eyes, surgery is performed on one eye at a time. The first eye heals before the second cataract is removed, sometimes as soon as the following week. A final eyeglass prescription is usually given about four to six weeks after surgery. Patients will still need reading glasses. The overall health of the patient must be considered in making the decision to have undergo cataract surgery. However, age alone need not preclude effective surgical treatment of cataracts, and people in their 90s can have successful return of vision after cataract surgery.

Surgery to remove cataracts is generally an outpatient procedure. A local anesthetic is used, and some newer techniques take only minutes to complete. Removal of the cloudy lens can be accomplished with one of the three types of cataract surgery available:

  • Extracapsular cataract extraction. In this type of cataract extraction, the lens and the front portion of the capsule are removed. The back part of the capsule remains in place.
  • Extracapsular cataract extraction by phacoemulsification. This type of extracapsular extraction requires only a very small incision, resulting in faster healing. Ultrasonic vibration is applied to the lens to break it up into very small pieces, and the ophthalmologist then aspirates the pieces out of the eye with suction. As of 2001, this is the most commonly performed type of cataract surgery.
  • Intracapsular cataract extraction. The lens and the entire capsule are removed. This method carries an increased risk for detachment of the retina and swelling after surgery, and, as a result, it is rarely used.

A replacement lens is inserted at the time of the surgery. A plastic artificial lens called an intraocular lens (IOL) is placed in the remaining posterior lens capsule of the eye. When the intracapsular extraction method is used, an IOL may be clipped onto the iris. Contact lenses and cataract glasses (aphakic lenses) are prescribed if an IOL cannot be inserted due to complications. A folding IOL is used with the phacoemulsification procedure to allow it to pass through the small incision.

Antibiotic drops to prevent infection and steroids to reduce inflammation are prescribed after surgery. An eye shield or glasses protect the eye from injury while it heals. During the night, an eye shield is worn. The patient returns to the doctor the day after surgery for assessment, with several follow-up visits over the next two months to monitor the healing process. Return visits at three and six months are optional.

Prognosis

The cataract extraction success rate is very high with a good prognosis. A visual acuity of 20/40 or better is expected as a result of cataract extraction. If an extracapsular cataract extraction was performed, a secondary cataract may develop in the remaining back portion of the capsule. This can occur one to two years after surgery. YAG capsulotomy is most often used for this type of cataract. YAG stands for yttrium aluminum garnet, the name of the laser used for this procedure. This is a painless outpatient procedure and requires no incision. The laser beam makes a small opening in the remaining back part of the capsule, allowing light through.

Complications occur in a very small percentage (3-5%) of surgical cataract extractions. Possible complications include infections, corneal edema (swelling), diplopia, bleeding, retinal detachment, iris prolapse or vitreous in the wound, intraocular lens dislocation, and the onset of glaucoma. Some problems may occur one to two days, or even several weeks, after surgery. Follow-up examinations should check the patient for haziness or redness in the eye, decrease in vision, nausea, and pain.

Health care team roles

Skilled ophthalmic technicians and assistants record the patient history and perform many of the preliminary tests. Depending on skill level, these ophthalmic assistants may perform measurement of visual acuity under both low and high illumination, biomicroscopy with pupillary dilation, assessment of ocular motility and binocularity, visual fields, evaluation of pupillary responses to rule out afferent pupillary defects, refraction, and measurement of intraocular pressure (IOP).

Before the surgery, nurses and assistants also prepare the operating room (OR). Many ophthalmologists now have their own ambulatory surgery centers (ASCs) where skilled technicians and ophthalmic nurses play a critical role in preparing the OR and patients for the surgery. Ophthalmic nurses also assist the ophthalmologist during surgery and discuss outcomes with patients post-operatively.

Patient education

When a cataract is found, the patient should be informed, even if surgery is not immediately indicated. The optometrist or ophthalmologist should discuss the different treatment options, as well as the risks and benefits of surgery with the patient.

Prevention

The eyes should be protected from UV radiation by wearing glasses with a special coating. Dark lenses alone are not sufficient, but the lenses must be coated to filter out UV light (specifically, UV-A and UV-B). Antioxidants also may help prevent cataracts by reducing free radicals that can damage lens proteins. A healthy diet rich in sources of antioxidants, including citrus fruits, sweet potatoes, carrots, green leafy vegetables, and/or vitamin supplements, may be beneficial. When taking certain medications, such as steroids, more frequent eye exams may be necessary. Patients should also be told not to smoke.

KEY TERMS

Glaucoma— Disease of the eye characterized by increased pressure of the fluid inside the eye. Untreated, glaucoma can lead to blindness.

Ultraviolet radiation (UV)— Invisible light rays that may be responsible for sunburns, skin cancers, and cataract formation.

Uveitis— Inflammation of the uvea. The uvea is a continuous layer of tissue which consists of the iris, the ciliary body, and the choroid. The uvea lies between the retina and sclera.

Resources

BOOKS

"Cataract." In Medical-Surgical Nursing: Concepts and Clinical Practice, edited by Wilma J. Phipps, et al. 5th ed. St. Louis: Mosby-Year Book, 1995, pp. 2088-2090.

PERIODICALS

"Nutrients and Cataract Risk in Older Individuals." Nutrition Research Newsletter 19 (July 2000): 15.

ORGANIZATIONS

American Academy of Ophthalmology (National Eyecare Project). P.O. Box 429098, San Francisco, CA 94142-9098. Phone: (800) 222-EYES. 〈http://www.eyenet.org〉.

American Optometric Association. 243 North Lindbergh Blvd., St. Louis, MO 63141. (314) 991-4100. 〈http://www.aoanet.org〉.

The Lighthouse. 111 East 59th Street, New York, NY 10022. (800) 334-5497. 〈http://www.lighthouse.org〉.

Prevent Blindness America. 500 East Remington Road, Schaumburg, IL 60173. (800) 331-2020. 〈http://www.prevent-blindness.org〉.

OTHER

Aker, Alan B., and David C. Brown. "How to Commit Efficiency." Ophthalmology Management Online. 〈http://www.ophmanagement.com/archive_results.asp?loc=archive/07182000104305am.html〉.

"Cataracts: No Nasal Spray Connection." Ophthalmology Management Online. 〈http://www.ophmanagement.com/archive_results.asp?loc=archive/0808200033819.html〉.

McCune, Donna M. "Are You Sharing Post-Op Care Correctly?" Ophthalmology Management Online. 〈http://www.ophmanagement.com/archive_results.asp?loc=archive/1013200014550pm.html〉.

"Optometric Clinical Practice Guideline: Care of the Adult Patient with Cataract." American Optometric Association Online. 〈http://www.aoanet.org/cpg-8-cpwc.html〉.

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Cataracts

Cataracts

Definition

A cataract is a clouding of the lens in the eye that affects vision.

Description

When a person looks at an object, light rays are reflected from the object to the person's eye. These light rays are bent and refracted by the cornea, the transparent, dome-shaped window at the front of the eye that provides refracting power, and 65–75% of the eye's focusing power. From the cornea, the light goes through the pupil, the circular opening in the center of the colored iris, and is sharply focused by the crystalline lens on the retina, the multi-layered sensory tissue that lines the back of the eye. It is on the retina that the light focused by the lens produces clear and sharp inverted images, converted to electrical impulses that are then transmitted through the optic nerve to the brain, where the image is perceived in an upright position.

The eye lens consists of four layers, from the surface to the center. The outer surface layer (capsule) is a thin, clear membrane that surrounds a soft, jellylike material (cortex). A layer of cells (subcapsular epithelium) joins the capsule and the cortex and the last layer is the hard center of the lens (nucleus). In a healthy eye, all the layers of the lens are clear, and light passes through unobstructed. However, if the lens material becomes cloudy, yellow, brown, and even opaque, with the result that light is obstructed from entering, the condition is referred to as a cataract.

Cataracts can develop in one or both eyes, but in most cases, they tend to develop in both. Moreover, the condition may or may not affect the entire lens. As a cataract develops, the lens becomes clouded, which scatters the light and prevents a sharply defined image from forming on the retina with the result that vision becomes blurred. Cataracts are classified into three types: nuclear, cortical, and subcapsular.

A nuclear cataract is the most common form of cataract. It forms in the nucleus, at the center of the lens. In its early stages, as the lens starts not to focus light normally, affected persons may become more nearsighted or experience a temporary improvement of their reading vision. However, as the lens gradually turns more yellow and opaque, vision clouds further and deteriorates. As the cataract progresses, the lens may eventually turn brown and causes a decrease in distance vision and in the ability to see in dim light.

A cortical cataract forms whitish spokes on the outer edge of the lens cortex that eventually extend to the center and interfere with light passing through the center of the lens. It may affect both near and distance vision with focusing problems and vision distortions.

A subcapsular cataract usually forms at the back of the lens, in the path of light to the retina. It may occur in both eyes, but tends to be more advanced in one eye than the other. A subcapsular cataract often affects reading vision, also reducing it in bright light.

How quickly cataracts develop varies among individuals and between the two eyes. Most age-related cataracts progress gradually over a period of years.

Demographics

Age-related cataract is a major public health problem. Worldwide it is the major cause of preventable blindness. Cataracts are a leading cause of visual impairment among aging Americans and represent an important quality of life issue. Cataract extractions are the most common surgical procedures performed in the United States, accounting for more

Prevalence of cataract among adults 40 years and older in the United States
Age Cataract
Years Persons (%)
source: Adapted from Archives of Ophthalmology, Vol. 122, April 2004
(Illustration by GGS Information Services. Cengage Learning, Gale)
40–491,046,0002.5%
50–592,123,0006.8%
60–694,061,00020.0%
70–796,973,00042.8%
≥806,272,00068.3%
Total 20,475,000 17.2%

than two million procedures each year. More than 50% of people over the age of 60 have some type of cataract. After age 75, as many as 70% of Americans have cataracts that are significant enough to impair vision.

Causes and symptoms

In young people, the lens changes its shape to adjust for close or distant vision, a process called “accommodation.” With aging however, the eye lenses gradually harden, and lose the ability to accommodate. They become less flexible and less transparent. This is because the protein fibers that make up the lens start breaking down with age. Some of the fibers start aggregating together, clouding small areas of the lens. As the cataract develops, the clouding becomes heavier and spreads to a greater part of the lens. Aging of the lens is not the only cause of cataracts. Some people are born with cataracts or develop them during childhood. Cataracts may also be produced by eye injury or trauma, including exposure to ultraviolet light and radiation. Diseases such as diabetes and hypertension may also lead to cataract formation, as well as eye surgical procedures (secondary cataracts).

Common cataract symptoms include:

  • cloudy or blurred vision
  • colors that appear faded or yellow
  • double vision in one eye
  • frequent prescription changes for eyeglasses or contact lenses
  • glare. Lamps, or sunlight appears too bright, halos may be seen around lights
  • light sensitivity

Diagnosis

Cataracts are detected following a complete eye examinations performed by an ophthalmologist or other eye care practitioner. Tests commonly used to establish diagnosis may include:

  • Visual acuity test. This test uses an eye chart that measures how well a person can see letters at a distance. Eyes are tested one at a time, keeping the other eye covered. Using an eye chart that displays progressively smaller letters from top to bottom, the test determines if a person has 20/20 vision (excellent) or less acute vision.
  • Dilated eye exam. In this test, drops are placed in the eyes to dilate the pupils. A magnifying lens is then used to examine the retina and optic nerve for signs of damage and other eye problems.
  • Tonometry. This test uses an instrument to measure the pressure inside the eye. Drops are used to numb the eye and a special device is used to measure the eye's inner pressure.

Treatment

In the early stages, when symptoms are mild, new eyeglasses, brighter lighting, anti-glare sunglasses, or magnifying lenses may prove effective. When vision loss interferes with everyday activities, surgery can be performed to remove the cloudy lens and replace it with an artificial lens.

Nutrition/Dietetic concerns

Several research reports show that the antioxidant properties of vitamins C and E may protect against the development and progression of cataracts. The Nutrition and Vision Project (NVP), a cooperative effort of Harvard and Tufts University researchers, found that higher intakes of vitamin C led to a reduced risk for cortical and nuclear cataracts. Results also showed that people who took vitamin C and E supplements for more than ten years had decreased progression of nuclear cataracts. Research also suggests that the carotenoids lutein and zeaxanthin, the only carotenoids found in the lens and which are also antioxidants , may also protect against cataracts.

QUESTIONS TO ASK YOUR DOCTOR

  • How is a cataract treated?
  • How do I know if cataract surgery is right for me?
  • Is cataract surgery effective?
  • Are there different types of cataract surgery?
  • What are the risks of cataract surgery?
  • Can problems develop after surgery?
  • After surgery, when will my vision be normal again?
  • What can I do to protect my vision?

Therapy

The only effective therapy for a cataract is surgery to replace the lens with a clear intraocular lens (IOL) implant, made of plastic, acrylic or silicone. Sometimes cataracts are removed without reinserting implant lenses. Two surgical procedures can be used to remove cataracts:

  • Phacoemulsification: In this procedure, the surgeon removes the cataract but leaves most of the outer layer (capsule) in place. The surgeon makes a tiny incision where the cornea meets the thin, transparent tissue that covers the outer surface of the eye (conjunctiva) and inserts a needle-like probe that uses ultrasound waves to break up the cataract and suctions out the fragments. The lens capsule remains in place to provide support for the IOL implant.
  • Extracapsular cataract extraction: This procedure requires a larger incision, made where the cornea and the white of the eye (sclera) meet. The surgeon opens the lens capsule, removes the hard nucleus in one piece and aspires out the softer lens cortex, leaving the capsule in place.

Once the cataract has been surgically removed, a clear artificial IOL is implanted into the empty lens capsule. It requires no care and becomes a permanent part of the eye.

Prognosis

The success rate of cataract surgery in restoring vision is excellent. Nine out of ten people that undergo the surgery regain good vision. Improved vision is achieved if other vision-limiting problems are not present.

KEY TERMS

Antioxidant —Any substance that reduces damage due to reactive oxygen such as that caused by free radicals.

Cataract —Opacity or cloudiness of the eye lens, which may prevent a clear image from forming on the retina.

Carotenoids —Red to yellow pigments responsible for the characteristic colour of many plant organs or fruits, such as tomatoes, carrots, etc.

Conjunctiva —The thin, transparent tissue that covers the outer surface of the eye.

Cornea —Transparent front part of the eye that covers the iris, pupil, and anterior chamber and provides most of an eye's optical power.

Dilated pupil —Enlarged pupil, resulting from contraction of the dilator muscle or relaxation of the iris. Occurs normally in dim illumination, or may be produced by certain drugs or trauma.

Iris —Pigmented tissue lying behind the cornea that gives color to the eye and controls amount of light entering the eye by varying the size of the pupil.

Lens —Transparent, biconvex crystalline tissue that helps bring rays of light to a focus on the retina.

Opaque —Impenetrable by light, neither transparent nor translucent, not reflecting light.

Pupil —Variable—sized black circular opening in the center of the iris that regulates the amount of light that enters the eye.

Retina —Light—sensitive tissue at the back of the eye.

Sclera —Tough, opaque tissue that serves as the eye's protective outer coat. Also called “the white of the eye.”

Prevention

Most cataracts occur with age and cannot be prevented. However, vision can be protected and delay the onset of cataracts by wearing sunglasses and a hat with a brim to block ultraviolet sunlight. Smoking should also be avoided and good nutrition has been shown to lower the risk of age-related cataract. Eating green leafy vegetables and fruits provide a good source of antioxidants. People aged 60 or older should have a comprehensive dilated eye exam at least once every two years.

Caregiver concerns

The American Academy of Ophthalmology estimates that, by age 65, 33% of Americans have some form of eye disease that impairs vision. Unfortunately, most people in this age group are unaware of these disorders because there are often no warning symptoms or they believe that poor sight is a natural consequence of aging. However, by detecting eye disease early through annual exams, seniors can preserve their sight longer. In the United States, the Seniors EyeCare Program ensures that every senior has access to medical eye care and promotes annual, dilated eye exams. It raises awareness about age-related eye disease, including cataracts, provides free eye care educational materials and facilitates access to eye care, at no cost to seniors. People eligible for a referral through the program receive a comprehensive, medical eye exam and up to one year of free treatment for any disease diagnosed during the initial exam.

Resources

BOOKS

Gimbel, Howard, and David Chang. Cataracts: A Patient's Guide to Treatment. Omaha, NE: Addicus Books, 2004.

Harvard Medical School. The Aging Eye. New York, NY: Free Press (Simon & Schuster), 2001.

Jae Yong, Kim. Essentials of Cataract Surgery. Thorofare, NJ: Slack Inc., 2007.

Mayo Clinic. Mayo Clinic On Vision And Eye Health: Practical Answers on Glaucoma, Cataracts, Macular Degeneration & Other Conditions. Scottsdale, AZ: Mayo Clinic Trade Paper, 2002.

Watts, Mark. Cataract: What You Need To Know. London, UK: Sheldon Press, 2006.

PERIODICALS

Chiu, C. J., and A. Taylor. “Nutritional antioxidants and age-related cataract and maculopathy.” Experimental Eye Research 84, no. 2 (February 2007): 229–245.

Ciulla, T. A., and B. R. Hammond. “Macular pigment density and aging, assessed in the normal elderly and those with cataracts and age-related macular degeneration.” American Journal of Ophthalmology 138, no. 4 (October 2004): 582–587.

Datta, S., et al. “The importance of acuity, stereopsis, and contrast sensitivity for health-related quality of life in elderly women with cataracts.

Investigative Ophthalmology & Visual Science 49, no. 1 (January 2008): 1–6.

Foss, A. J., et al. “Falls and health status in elderly women following second eye cataract surgery: A randomised controlled trial.” Age and Ageing 35, no. 1 (January 2006): 66–71.

Hejtmancik, J. F., and M. Kantorow. “Molecular genetics of age-related cataract.” Experimental Eye Research 79, no. 1 (July 2004): 3–9.

Kulmala, J., et al. “Lowered vision as a risk factor for injurious accidents in older people.” Aging Clinical Experimental Research 20, no. 1 (February 2008):25–30.

Zubenko, G. S., et al. “Reduced age-related cataracts among elderly persons who reach age 90 with preserved cognition: a biomarker of successful aging?” The Journals of Gerontology A 62, no. 5 (May 2007): 500–506.

OTHER

Cataract. NIH Senior Health. April 9, 2007 (February 20, 2008) http://nihseniorhealth.gov/cataract/toc.html.

Cataracts. EyeCare America. May 2007 (February 20, 2008) http://www.eyecareamerica.org/eyecare/conditions/cataracts/index.cfm.

Cataracts. Mayo Clinic. May 19, 2006 (February 20, 2008) http://www.mayoclinic.com/health/cataracts/DS00050.

Cataract. National Eye Institute. April 2006 (February 20, 2008) http://www.nei.nih.gov/health/cataract/cataract_facts.asp.

ORGANIZATIONS

American Academy of Ophthalmology (AAO), P.O. Box 7424, San Francisco, CA, 94120-7424, (415) 561-8500, (415) 561-8500, [email protected], http://www.aao.org.

EyeCare America, 655 Beach St., San Francisco, CA, 94109-1336, (877) 887-6327, (800) 222-3937, http://www.eyecareamerica.org/eyecare.

National Eye Institute, 2020 Vision Place, Bethesda, MD, 20892-3655, (301) 496-5248, [email protected], http://www.nei.nih.gov/.

Monique Laberge Ph.D.

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