Cataracts
Highlights
Cataracts
Cataracts are a common age-related vision problem. About 20.5 million Americans age 40 and older have cataracts, and the older a person gets the greater the risk for developing cataracts. Women are more likely to develop cataracts than men, and African Americans and Hispanic Americans are at particularly high risk.
In addition to age, other factors may increase the risk of cataract development. These include:
- Diabetes
- Smoking
- Over-exposure to sunlight
Symptoms
During the early stages, cataracts may have little effect on vision. Symptoms vary due to the location of the cataract in the eye (nuclear, cortical, or posterior subcapsular). Depending on the type and extent of the cataract, patients may experience the following symptoms:
- Cloudy vision
- Double or blurry vision
- Glare and sensitivity to bright lights
- Colors appear faded
- Difficulty reading due to reduced black-white contrast
Treatment
Cataracts never go away on their own, but some stop progressing after a certain point. But if cataracts continue to grow and progress, they can cause blindness if left untreated. Fortunately, cataracts can usually always be successfully removed with surgery. Millions of cataract surgeries are performed each year in the United States, and there is a very low risk for complications. However, before opting for surgery, patients need to consider on an individual basis how severely a cataract interferes with their quality of life. Cataract surgery is rarely an emergency, so patients have time to consult with their doctors and carefully consider the risks and benefits of surgery.
Cataract Removal Surgery
Surgery involves removing the cataract and replacing the abnormal lens with a permanent implant called an intraocular lens (IOL). The operation takes less than 1 hour and is performed on an outpatient basis. The procedure is generally painless and most patients remain awake during it. If you have cataracts in both eyes, doctors recommend waiting at least 1 month between surgeries.
Introduction
A cataract is an opacity, or clouding, of the lens of the eye.
The prevalence of cataracts increases dramatically with age. It typically occurs in the following way:
- The lens is an elliptical structure that sits behind the pupil and is normally transparent. The function of the lens is to focus light rays into images on the retina (the light-sensitive tissue at the back of the eye).
- In young people, the lens is elastic and changes shape easily, allowing the eyes to focus clearly on both near and distant objects.
- As people reach their mid-40s, biochemical changes occur in the proteins within the lens, causing them to harden and lose elasticity. This causes a number of vision problems. For example, loss of elasticity causes presbyopia, or far-sightedness, requiring reading glasses in almost everyone as they age.
- In some people, the proteins in the lens, notably those called alpha crystallins, may also clump together, forming cloudy (opaque) areas called cataracts. They usually develop slowly over several years and are related to aging. In some cases, depending on the cause of the cataracts, loss of vision progresses rapidly.
- Depending on how dense they are and where they are located, cataracts can block the passage of light through the lens and interfere with the formation of images on the retina, causing vision to become cloudy.
Click the icon to see an image of eye anatomy.
Cataracts can form in any of three parts of the lens and are named by their location.
- Nuclear cataracts. These form in the nucleus (the inner core) of the lens. This is the most common variety of cataract associated with the aging process.
- Cortical cataracts. These form in the cortex (the outer section of the lens).
- Posterior subcapsular cataracts. These form toward the back of a cellophane-like capsule that surrounds the lens. They are more frequent in people with diabetes, who are overweight, or those taking steroids.
Causes
Although older age is the primary risk factor for cataracts, experts are still not certain about the exact biologic mechanisms that tie cataracts to aging.
Researchers have been focusing on particles called oxygen-free radicals as a major factor in the development of cataracts. They cause harm in the following way:
- Oxygen-free radicals (also called oxidants) are molecules produced by natural chemical processes in the body. Toxins, smoking, ultraviolet radiation, infections, and many other factors can create reactions that produce excessive amounts of these oxygen-free radicals.
- Oxidants are missing an electron, so they are unstable and tend to chemically bind with other molecules in the body. When oxidants are overproduced, these chemical reactions can be very harmful to nearly any type of cell in the body. At times these reactions can even affect genetic material in cells.
- Cataract formation is one of many destructive changes that can occur with overproduction of oxidants, possibly in concert with deficiencies of an important protective anti-oxidant called glutathione.
- Glutathione occurs in high levels in the eye and helps clean up these free radicals. One theory posits that in the aging eye, barriers develop that prevent glutathione and other protective antioxidants from reaching the nucleus in the lens, thus making if vulnerable to oxidation.
Sunlight and Ultraviolet Radiation. Sunlight consists of ultraviolet (referred to as UVA or UVB) radiation, which penetrates the layers of the skin. Both have destructive properties that can promote cataracts. The eyes are protected from the sun by eyelids and the structure of the face (overhanging brows, prominent cheekbones, and the nose). Long-term exposure to sunlight, however, can overcome these defenses.
- UVB radiation produces the shorter wavelength, and primarily affects the outer skin layers. It is the primary cause of sunburn. It is also the UV radiation primarily responsible for cataracts. Long-term exposure to even low levels of UVB radiation can eventually cause changes in the lens, including pigment changes, which contribute to cataract development. (UVB also appears to be responsible for macular degeneration, an age-related disorder of the retina.) Some scientists suggest that global warming and ozone depletion may increase people’s exposure to UVB, leading to a greater incidence of cataracts.
- UVA radiation is composed of longer wavelengths. They penetrate more deeply and efficiently into the inner skin layers and are responsible for tanning. The main damaging effect of UVA appears to be the promotion of the release of oxidants.
Radiation Treatments. Cataracts are common side effects of total body radiation treatments, which are administered for certain cancers.
Electromagnetic Waves. Questions have been raised about the hazards of low-level radiation from computer screens. To date, no study has demonstrated an association between cataract development and video display terminals. It is a good idea, in any case, to sit at least a foot away from the front of a screen.
Corticosteroids. Long-term use of oral steroids is a well-known cause of cataracts. Studies have been conflicting, however, over whether inhaled and nasal-spray steroids increase the risk for cataracts. Information on cataract risk from inhaled steroids is important because they are commonly used by asthma patients, and steroid spray use is increasing among allergy sufferers. Studies have suggested a higher risk for cataracts among middle-aged and elderly patients treated with beclomethasone (Beclovent, Vanceril). However, newer inhaled steroids are available, and their effects on the eye are unclear. In children, cataracts are rare, and the benefits of inhaled steroids for asthma far outweigh any small additional risk.
Other Medications Associated with Cataracts.
- Psoralens, a class of drugs used along with light therapy to treat skin disorders, such as psoriasis
- Antipsychotic medications such as chlorpromazine (Thorazine)
- Glaucoma medications
Many others drugs have been weakly associated with cataracts, including allopurinol, tamoxifen, amiodarone, tricyclic antidepressants, potassium-sparing diuretics (but not other diuretics), thyroid hormone, tetracyclines, sulfamidase, and mepacrine. Statin drugs (used for managing cholesterol) may possibly reduce the risk for nuclear cataracts.
Click the icon to see an animation about cataracts.
Glaucoma. Glaucoma and its treatments, including certain drugs (notably miotics) and filtering surgery, pose a high risk for cataracts. The glaucoma drugs posing a particular risk for cataracts including demecarium (Humorsol), isoflurophate (Floropryl), and echothiophate (Phospholine).
Uveitis. Uveitis is chronic inflammation in the eye, which is often caused by an autoimmune disease or response. Often the cause is unknown. It is a rare condition that carries a high risk for cataracts.
A number of medical conditions appear to be associated with a higher risk for cataracts either because of a direct effect or because of the medications used for them, or both. They include the following:
- Diabetes. Cataracts in patients with diabetes appear to form when high levels of blood sugar react with proteins in the eye to form byproducts that accumulate in the lens (sugar cataracts).
- Autoimmune diseases including rheumatoid arthritis, psoriasis, multiple sclerosis, systemic lupus erythematosus, Behcet's disease, and others.
Rarely, about 1 in every 10,000 births, a baby is born with cataracts (called congenital cataracts).
- Inherited disorders are often involved in the development of congenital cataracts in children. Such cataracts are most often due to inborn abnormalities in the structure or shape of the lens, including its capsule. Dozens of variations can affect the lens causing, susceptibility to cataracts. Researchers are also investigating genetic factors that may cause mutations in alpha crystallins -- major proteins in the lens, which form cataracts. (Genetic factors also may play a role in some adult cataract cases. The exact hereditary predispositions have yet to be established.)
- Infection during pregnancy can lead to cataracts.
- Pregnant women who abuse alcohol or drugs increase the risk for cataracts (along with other more serious birth defects) in their infants.
Surgery in children with early-onset cataracts can help correct this problem in many cases, but it should be performed as soon as possible for full benefit. Experts recommend routine examination of the face of a fetus during ultrasound for abnormalities.
Symptoms
During the early stages, cataracts have little effect on vision. The symptoms of a cataract may include:
- Cloudy vision, double vision, or both may be the first signs.
- Images may take on a yellowish tint as color vibrancy diminishes.
- Reading may become difficult over time because of a reduced contrast between letters and their background.
- Sensitivity to bright lights may make it difficult or impossible to drive at night because of glare from the headlights of oncoming cars. (People with diffuse cataracts in the rear walls of their lenses are particularly prone to glare sensitivity because bright light tends to scatter in their lenses.)
- In very advanced cases, the pupil, which is normally black, looks milky or yellowish. The patient's vision is reduced to being able only to distinguish light from dark.
Symptoms may vary depending on the part of the lens that is affected.
Nuclear Cataracts. Cataracts of the lens nucleus are most commonly associated with aging. Symptoms include:
- Hazy distance vision and increasing glare.
- Progressive nearsightedness and the need for frequent changes in eyeglass prescriptions. This effect may even temporarily counteract age-related farsightedness and provide a temporary improvement in overall vision in some people. The improvement fades when the cataract advances sufficiently to overwhelm the inherent farsightedness. Eventually, as the cataracts grow worse, stronger glasses can no longer correct the patient's vision.
Click the icon to see an image of normal, near, and farsighted vision.
Cortical Cataracts. Cortical cataracts usually start on the outside of the cortex (the outer area of the lens).
- They have very little initial effect on vision.
- Glare can develop as these cataracts increase and approach the center of the lens.
- Problems with distance vision, contrast sensitivity, and clarity may occur as the cataracts progress further.
Posterior Subcapsular Cataracts. Posterior subcapsular cataracts typically start near the center of the back part of the capsule surrounding the lens. These cataracts often advance rapidly. For many patients, major impairment of eyesight, including near-vision problems and glare, develops within several months.
Prognosis
Some cataracts stop progressing after a certain point. Cataracts are never reversible, however, even after eliminating factors (such as drugs or illnesses), which might have promoted their development. If extensive and progressive cataracts are left untreated they can cause blindness. In fact, cataracts are the leading cause of blindness among adults age 55 and older. About 20.5 million Americans have at least one cataract. By 2020, that number is expected to jump to 30.1 million.
Fortunately, cataracts nearly always can be successfully removed with surgery. However, surgery is unavailable in certain parts of the world, leaving millions at risk for vision loss. Even in the U.S., where surgery has greatly reduced the risk of blindness, tens of thousands still lose their sight and millions more have poor vision because of cataracts. Cataracts also create a financial burden. According to 2006 data, cataracts cost the U.S. nearly $7 billion each year in medical services and drug treatments.
A number of studies have shown that cataracts are associated with shortened lifespan. Some studies have specifically suggested poorer survival in patients with nuclear or mixed cataracts but not in those with cataracts in the cortex or capsule. In any case, nuclear cataracts are highly associated with smoking and diabetes, although some studies have found lower survival rates in patients with nuclear cataract regardless of these health risks.
An increased rate of automobile accidents is found among patients who do not have cataract surgery compared to those who had surgery. This finding, however, is obscured by the possibility that patients who choose not to have surgery may have other health problems that put them at risk for accidents. Also, driving skills decline with age in nearly everyone. Cataract surgery, then, is no insurance against age-related accidents.
Reduced vision ranks third only behind arthritis and heart disease as a cause of impaired function in older people. Extensive cataracts can compromise the ability to earn a living, read, drive, or live independently. Although vision loss has been associated with a number of major adverse effects, few studies have reported on the effect of vision on daily activities.
Both blurred vision and problems in seeing contrasts contribute to impaired activity. The degree of these impairments, however, may have different effects on disability depending on individual tasks and needs. For example, even a slight loss in vision sharpness and contrast can impair the ability to recognize faces or slow down reading speed. For those who read very quickly, this may not be significant, but it could be very disabling for slower readers.
Nevertheless some people who have small cataracts can see well enough around the clouded areas to live normally. But for many people, cataracts are extensive enough to interfere greatly with daily activities.
Risk Factors
Aging is the primary risk factor for cataracts, but other factors are also involved.
Nearly everyone who lives long enough will develop cataracts to some extent. A major study reported that:
- About 40% of people age 55 - 64 years had some opaque areas in their lenses, and 5% had fully-developed cataracts.
- About 70% of people age 65 - 74 years had opaque areas, and 18% had cataracts.
- More than 90% of people age 75 - 84 years had opaque areas, and almost 50% had cataracts.
One study indicated that posterior subcapsular cataracts are the most common type in people under 70 years old, while nuclear and mixed cataracts are most common in people over age 80. The risk for nuclear cataracts also increases with age.
Women face a higher risk than men. Women who started menstruating late are at an even higher risk.
Eye Features. People who are nearsighted and those with brown eyes may be at higher than average risk. (Not all studies, however, report a higher risk in people with darker eyes.)
Obesity and Height. Studies are now reporting obesity as a risk factor for cataracts, notably posterior subcapsular cataracts, which form toward the back of the lens.
African-Americans seem to have nearly twice the risk of developing cataracts than do Caucasians. This difference may be due to other medical illnesses, particularly diabetes. African-Americans are much more likely to become blind from cataracts and glaucoma than Caucasians, mostly due to lack of treatment.
Hispanic Americans are also at increased risk for cataracts. In fact, cataracts are the leading cause of visual impairment among Hispanics.
People with certain medical conditions, notably diabetes, are at high risk for cataracts, either because of a direct effect of the disease, its treatments, or both.
Autoimmune Diseases and Conditions Requiring Steroid Use. Medical conditions requiring high use of corticosteroids (commonly called steroids) pose a particularly high risk. Many of these medical conditions are autoimmune diseases, including rheumatoid arthritis, psoriasis, multiple sclerosis, systemic lupus erythematosus, Behcet's disease, and others.
Diabetes and People with High Blood Glucose Levels. People with diabetes type 1 or 2 are at very high risk for cataracts and are much more likely to develop them at a younger age. They also have a higher risk for nuclear cataracts than nondiabetics. Cataract development is significantly related to high levels of blood sugar (called glycemia), and cataracts in people with diabetes are sometimes referred to as so-called sugar cataracts. Even people without diabetes but with higher-than-normal blood sugar levels are at high risk for cataracts. Some doctors now recommend that children with diabetes undergo an eye exam to check for cataracts at the time they are diagnosed.
Exposure to even low-level UVB radiation from sunlight increases the risk for cataracts, especially nuclear cataracts. The risk may be highest among those who have significant sun exposure at a young age. Studies suggesting risk associated with sunlight exposure also report:
- The closer people live to the equator, the greater the chance for cataracts. Light exposure in these climates also increases the risk for severe cortical or mixed cataracts. Even wearing sunglasses may not reduce the risk for these cataracts.
- People whose jobs expose them to sunlight for prolonged periods are at higher risk. People in southern climates whose occupations, such as fishing or oyster farming, exposed them to very intense sunlight were at high risk for all cataracts, including posterior subcapsular cataracts. (People in more northern climates with similar occupations may not have as high a risk.)
- Occupational exposure to very intense artificial light, such as arc welding, increases the risk for cataracts.
Smokers. A study of nearly 18,000 doctors showed that those who smoked 20 or more cigarettes a day had about twice the risk of developing cataracts. Smokers are at particular risk for cataracts located in the nuclear portion of the lens, which limit vision more severely than cataracts in other sites. Quitting smoking may reverse some of this damage.
Alcohol Users. Chronic drinkers are at high risk for a number of eye disorders, including cataracts. Alcohol has been implicated in cataract development in a number of studies. Wine provided the least risk, and the more moderate the drinking the lower the risk. Alcohol may work directly on the proteins in the lens itself and indirectly by affecting absorption of nutrients important to the lens.
Long-term environmental lead exposure may increase the risk of developing cataracts. Gold and copper accumulation may also cause cataracts.
A poor diet may deprive the body of amino acids and B vitamins that are essential for eye health.
Other conditions that can trigger the process leading to cataracts include:
- Physical injury to the eye (such as a hard blow, cut, or puncture)
- Chemical burns
- Electrical shock injuries
- Chronic exposure to intense heat or cold
Prevention
Although cataracts are not completely preventable, their occurrence can be delayed. Quitting smoking, avoiding overexposure to sunlight, drinking alcohol in moderation, and eating plenty of fresh fruits and vegetables can delay the formation of cataracts. No existing evidence suggests that using eye drops or ointments or performing eye exercises will stem the onset of cataracts.
The simplest and most effective way to protect against ultraviolet (UV) radiation is to stay out of the sun. Wear a hat and cover-up outside, particularly when the sun is most intense (10 a.m. - 3 p.m.). A wide-brimmed hat can reduce eye exposure to UVB radiation by 30 - 50%. Because the sun's rays are highly reflective, sitting in the shade or under an umbrella by itself does not guarantee protection.
Note: Avoidance of the sun should not be taken to extremes. Some sunshine is desirable. Moderate sun exposure provides an important source of vitamin D, which is essential for healthy bones. There is a link between lack of sun exposure and depression (known as seasonal affective disorder, or SAD).
Click the icon to see an image of vitamin D.
Sunglasses. Protective sunglasses do not have to be expensive. Sunglasses are classified into three categories based on UVA and UVB protection:
- Cosmetic purpose sunglasses block at least 70% UVB and up to 60% UVA. People should avoid these glasses if they have any risk for cataracts or eye problems.
- General purpose sunglasses block at least 95% UVB and a minimum of 60% UVA. At the very least, people should purchase general purpose sunglasses that are labeled "Meets ANSI Z80.3 General Purpose UV Requirements." Labels should indicate that sunglasses block UV radiation up to 400 nm.
- Special purpose sunglasses block at least 99% UVB and a minimum of 60% UVA rays. These are the optimal sunglasses for people at risk for cataracts. Ideally they should have the Skin Cancer Foundation's Seal of Recommendation for Sunglasses. Special purpose glasses should wrap around the head and block light coming from above, below, and both sides of the glasses. They should also fit snugly on the nose.
- Lenses that are simply dark but not coated with UV-absorbing material may actually increase the risk of cataracts because the pupil widens to compensate for the shaded glass. This may allow more harmful ultraviolet waves to enter. Polarized glasses cut glare but have no effect on UV radiation. Mirror finishes without additional processing for UV blockage are also not fully protective. There is some controversy over whether blue light is harmful to the eyes. Some people prefer amber lenses, which block out the blue spectrum.
Vitamins. Because of the role oxidants may play in cataract formation, researchers are investigating the benefits of antioxidant vitamins and other food chemicals. Vitamins C, E, and riboflavin (a B vitamin), for example, are helpful in preserving levels of glutathione, an enzyme that helps protect against oxidation in the eye. Low levels of vitamin C in the lens of the eye have been particularly strong predictors of cataracts. Some evidence also suggests that ultraviolet B radiation interacts with deficiencies in certain antioxidants, such as vitamin E and zinc, to increase damage in the corneas and lenses of the eye.
Evidence on the benefits of supplements of vitamin E or C, or vitamin-rich foods, is conflicting. For example, in two identically constructed trials in the U.S. and Britain, the American group derived apparent benefits from vitamins E, C, and beta carotene while the British group reported very little cataract protection. A 2005 study suggested that long-term use of vitamin E supplements may slow cataract development. However, in a major on-going American study called the Age-Related Eye Disease Study (AREDS), researchers reported no difference in the incidence of cataracts after 7 years in people who took the antioxidant vitamins compared to those who took placebos.
High doses of vitamins may have harmful effects. It is always wise, in any case, to pursue a healthy diet that is low in fats, high in complex carbohydrates, and rich in fruits and vegetables.
Carotenoids. Carotenoids are a group of more than 700 fat soluble nutrients that produce the colors in foods such as carrots, pumpkins, sweet potatoes, tomatoes, and other deep green, yellow, orange, and red fruits and vegetables. Many are proving to be very important for health. Different carotenoids may be more beneficial then others. They include:
- Xanthophylls compounds that form a particular category of carotenoids. The xanthophylls lutein and zeaxanthin are found in the lenses of the eye and may be of significant importance for people at risk for cataracts. Some evidence indicates supplements of xanthophyll-rich foods (such as dark green leafy vegetables) may help retard the aging process in the eye and protect against cataracts. However, in a review of the carotenoids lutein and zeaxanthin, the Food and Drug Administration concluded there is not enough evidence to suggest that taking supplements with these carotenoids lowers the risk of cataract formation.
- Beta-carotene is the most widely studied carotenoid and is a powerful antioxidant. It has been specifically studied for cataract protection. Most studies, however, have found little or no benefits.
- Lycopene is another carotenoid that may possibly play a role in eye health. Tomatoes are a rich source of lycopene.
Phytochemicals. Phytochemicals are substances in plants that have beneficial effects. Dark colored (green, red, purple, and yellow) fruits and vegetables usually have high levels of important plant chemicals and have been associated with a lower risk for cataracts. Tea contains certain plant chemicals called polyphenols that have been associated with protection against cataracts.
Click the icon to see an image of phytochemicals.
Diagnosis
Either an ophthalmologist or an optometrist can examine patients for cataracts, but only ophthalmologists are qualified to treat cataracts.
- An ophthalmologist is a doctor who specializes in the medical and surgical care of the eye.
- An optometrist practices eye care, but does not perform surgery.
The eye professional can observe cloudy areas on the lenses with a direct physical examination, even before the cataracts begin to interfere with vision. Cameras can measure the cataract density. Various vision tests are also performed.
Snellen Eye Chart. To determine how clearly a person can actually see, the Snellen eye chart is used, with rows of letters decreasing in size:
- From a specified distance, usually 20 feet, a person reads the letters using one eye at a time.
- If a person can read down to the small letters on the line marked 20 feet, then vision is 20/20 (normal vision).
- If a person can read only down through the line marked 40 feet, vision is 20/40; that is, from 20 feet the patient can read what someone with normal vision can read from 40 feet.
- If the large letters on the line marked 200 feet cannot be read with the better eye, even with glasses, the patient is considered legally blind.
Other Tests. A number of other tests are used to diagnose cataracts or to determine if surgery is needed.
- A chart similar to the Snellen chart, which has the same size letters, but in different contrasts with background, is used to test contrast sensitivity.
- Glare sensitivity is tested by having the patient read a chart twice, with and without bright lights.
- Tests of macular function, which evaluate the eye's acute vision center, can help the ophthalmologist determine the expected improvement from surgery.
- The corneal endothelium, a layer of cells lining the cornea, is sensitive to surgical trauma and should be evaluated before any intraocular operation.
- Patients with other eye disorders may need other pre-operative tests.
Although eye tests help confirm a diagnosis of cataracts, results do not always reflect the quality of life and how effectively people function at home:
- Some people with cataracts perform poorly on the tests yet appear to have no trouble with daily function.
- Others perform well on the tests but insist that their eyesight is bad enough to interfere with ordinary activities, such as driving.
Treatment
Although surgery is the only remedy for cataracts, it is almost never an emergency. Most cataracts cause no problem other than reducing a person's ability to see, so there is no harm in delaying surgery.
Early cataracts may be managed with the following measures:
- Stronger eyeglasses or contact lenses
- Use of a magnifying glass during reading
- Strong lighting
- Medication that dilates the pupil. (This may help some people with capsular cataracts, although glare can be a problem with this treatment.)
Progression of Cataracts. Patients and their families usually have plenty of time to carefully consider options and discuss them with an ophthalmologist. There is no constant rate at which cataracts progress:
- Some catracts develop to a certain point and then stop.
- Even if a cataract does progress, it may be years before it interferes with vision.
- Very rarely do people neeed immediate cataract surgery.
Cataract removal is the one of the most common type of eye surgeries performed in the United States, especially for people over age 65. Cataract surgery may be the oldest procedure in the world, having been introduced to Europe from India by the arm y of Alexander the Great.
In the past, cataract surgery was not performed until the cataract had become well developed. Newer techniques, however, have made it safer and even more efficient to operate in earlier stages. In fact, modern cataract techniques not only remove cataracts but also are becoming important procedures for correcting astigmatism. Cataract surgery improves vision in up to 95% of patients and prevents millions of Americans from going blind.
Nevertheless, considerable evidence suggests that, because of the ease and relative safety of the procedure, it may be performed more often than needed. Patients having operations now tend to have better preoperative vision than those operated on 10 - 20 years ago.
In general, even if cataracts are diagnosed, the decision to remove them should be based on the patient's own perception of vision difficulties and needs and the effect of vision loss on normal activity. The patient should also be aware of all the risks and costs of surgery. In order to determine the quality of life, the patient may be given a questionnaire such as the National Eye Institute Visual Function Questionnaire, which asks 39 questions related to vision and daily activities. This test or others may be useful for determining if eye disease is actually impairing the ability to function.
In general, surgery is indicated for people with cataracts under the following circumstances:
- The Snellen eye test reports 20/40 or worse, with a cataract being responsible for vision loss that cannot be corrected by glasses.
- Performing everyday activities has become difficult to perform to the point that independence is threatened, or the patient is at risk for accident or injury.
These guidelines are general, however. Whether surgery is appropriate or not further depends on the cataract patient's specific condition and needs. Some examples include:
- Even if the criteria for surgery are met, a very sick, elderly person in a nursing home may have less need for sharp vision than an active younger adult. Among very elderly patients (85 years and older), especially those with serious health problems, there are also higher risks for complications during surgery and poor outcomes afterward. Nevertheless, these cautions should not prevent the elderly from having this procedure; vision improvement rates are still over 85%.
- Even if the criteria for surgery are not met, some people with eye tests of 20/40 or better might want surgery because of problems with glare, double vision, or the need to have an unrestricted driver's license.
- Even if the criteria for surgery are not met, if retinal disease is also suspected (usually a complication of diabetes), the doctor may perform cataract surgery in order to have a clear view of the eye.
Because of the risks, albeit small ones, of poorer vision or blindness, no one should be forced to have cataract surgery if they don't want it or are not strong enough to have the procedure. If there are any doubts about whether or not to have cataract surgery, consider a second opinion.
Treatment Decisions for Cataracts in the Second Eye. If a person has a cataract in a second eye, the issues for decision making are the same as for the first eye. The time of the procedure in the case of two cataracts is unclear. Doctors have long recommended postponing surgery on the second eye until the first eye has healed and the results are known. However many patients have trouble reading and performing ordinary tasks while waiting for a second surgery. Patients with double cataracts should discuss all options with their surgeon.
The patient should ask the ophthalmologist the following questions before agreeing to cataract surgery:
- Is my cataract surgery an emergency?
- Are the cataracts the only cause of my poor vision?
- How much experience do you have with this procedure?
- Do I have other eye diseases that might complicate surgery or reduce my benefit?
- Do I have other health problems that might further complicate eye surgery?
- Will you implant an intraocular lens?
- What type of procedure will you use?
- Afterwards, what are my chances of having poorer vision or becoming totally blind in that eye?
- How well should I ultimately be able to see out of the operated eye?
- How long will it take to heal?
- What precautions should I take during the healing process?
- How long will it take to achieve my best eyesight?
- Will I have to wear glasses or contact lenses after surgery?
- When will I get my final eyeglass prescription?
- How soon after surgery will I be able to see well enough to go back to work? Drive a car? Return to full activity?
- What will the surgery cost?
Cataract surgery is now usually done as an outpatient procedure under local anesthesia and takes less than an hour. Preoperative preparations may include:
- Having a general physical examination is important for patients with medical problems such as diabetes. Diabetes can cause damage to the blood vessels of the eye’s retina, a condition called diabetic retinopathy. Recent research suggests that patients who have diabetic retinopathy and poor blood sugar control should not have their blood sugar rapidly corrected before cataract surgery. Correcting blood sugar too quickly before surgery can cause vision problems after surgery.
- The ophthalmologist will use a painless ultrasound test to measure the length of the eye and determine the type of replacement lens that will be needed after the operation.
- Topical application of so-called fluoroquinolone antibiotics (such as ofloxacin or ciprofloxacin) may be applied preoperatively to protect against postoperative infection.
- Most healthy patients receive either a local injection or topical anesthetic. Patients who get a sedative followed by a local injection report the least pain during the operation.
- Some patients may need a general anesthetic, such as those who have anxiety, are unable to cooperate with the surgeon, or are allergic to local anesthetics.
All cataract procedures involve removal of the cataract-affected lens and replacing it with an artificial lens.
Phacoemulsification. Phacoemulsification (phaco means lens; emulsification means to liquefy) is now the most common cataract procedure in the United States and accounts for 85% of cases. Benefits are greater than with standard extracapsular surgery, and it may be particularly helpful for people with diabetes.
The procedure generally involves:
- The surgeon makes an incision, which is much smaller than with standard cataract extraction.
- Ultrasound is then used to break up the clouded lens into small fragments.
- The tiny pieces are sucked out with a vacuum-like device.
- A replacement lens is then usually inserted into the capsular bag where the natural lens used to be. In most cases, this is an intraocular lens (IOL), which is foldable and slips in through the tiny incision.
- Because the incision is so small, it is often watertight and does not require a suture afterward, particularly if a foldable lens has been used. A suture may be needed if a tear or break occurs during the procedure or the surgeon inserts a rigid lens that requires a wider incision.
Click the icon to see an illustrated series detailing cataract surgery.
Phacoemulsification requires only local anesthesia. Newer methods for administering local anesthesia produce few complications. Most phacoemulsification procedures now take about 15 minutes, and the patient is usually out of the operating room in about an hour. There is little discomfort afterward, and visual rehabilitation takes about 1 - 3 weeks.
Phacoemulsification is sometimes combined with glaucoma surgical procedures, for patients who have both glaucoma and cataracts.
Extracapsular or Intracapsular Cataract Extraction. Extracapsular cataract extraction, the original standard procedure, is now generally used only in patients who have an extremely hard lens. It typically involves the following steps:
- The ophthalmologist works under an operating microscope to make a small incision in the cornea of the eye.
- The surgeon then extracts the clouded lens through this incision.
- The capsule is left in place, which adds structural strength to the eye and enhances the healing process. (Less commonly in intracapsular cataract extraction, the surgeon removes the lens and the entire capsule. This procedure has greater risks for swelling and retinal detachment.)
- A replacement lens is then usually inserted.
- A small suture is needed to stitch the incision together.
It takes about 2 - 4 weeks to completely restore vision.
With the clouded lens removed, the eye cannot focus a sharp image on the retina. A replacement lens or eyeglass are therefore needed:
Intraocular Lenses (IOL). In about 90% of cataract operations, an artificial lens, known as an intraocular lens (IOLs), is inserted. Until recently, IOLs used a pair of little spring-loaded loops to hold the lens in place. Most IOLs are now foldable, which makes insertion easier. In fact, a prefolded lens is now available that unrolls to fit the eye as body temperature warms it.
Although all the lens materials are presumably chemically inert, there are some reports of specific problems, notably a risk for causing a reaction that leads to the development of secondary cataracts, a condition called posterior capsular opacification. IOLs include the following materials:
- Acrylic: The majority of IOLs are made from acrylic, which allows a controlled unfolding of the lens. Evidence indicates that this material provides a better visual outcome and fewer complications than other standard IOLs.
- Polymethylmethacrylate (PMMA): Has the longest safety record. A PMMA IOL coated with heparin, a blood thinner drug, helps protect against the development of a secondary cataract after surgery.
- Silicone: Can be inserted through a smaller incision than other materials. It has the highest rates of secondary cataracts. Newer forms of silicon IOLs may pose a lower risk.
Other materials are under investigation.
IOLs are designed to improve specific aspects of vision. The choices include:
- Lenses that address a single fixed focal point. Such lenses are suitable either for reading or distance vision, but not both. If a distance lens is implanted, the surgeon prescribes glasses or contact lenses for reading. If a reading lens is implanted, lenses for seeing distances will be prescribed.
- Lenses that address multifocal points. Multifocal lenses can focus at different points for both reading and distance vision. However, contrast may be reduced, and some patients experience glare and halos, particularly at night.
- Lenses are available that will correct astigmatism after cataract surgery.
The patients and the doctor must make these decisions based on specific visual needs.
Contact Lenses or Cataract Glasses. A few patients do not receive a new lens and rely solely on corrective eyeglasses or contact lenses. Such patients may include:
- Patients who are extremely near-sighted
- Patients with other eye disorders
In such cases, the patient typically returns to the ophthalmologist for a check up the day after surgery, and three additional check-ups are scheduled over a 2-month period. The ophthalmologist can usually give a final prescription for eyeglasses or contact lenses about three months after surgery.
- Choosing Contact Lenses. Contact lenses allow clear vision but do not magnify, so those who choose contact lenses after surgery may have to wear reading glasses. Contacts can be prescribed either for use only during the day or for extended-wear. Occasionally contact lenses cause problems, such as infection. Those who wear them should call their eye doctor if they have red or watery eyes, pain, or sensitivity to light.
- Cataract Glasses. Until the advent of contact lenses, people who had cataract surgery had no choice but to wear glasses with thick lenses, sometimes called Coke-bottle glasses. These glasses have gotten thinner and lighter in recent years, but they may still be cumbersome. Cataract glasses are different from ordinary glasses and are sometimes difficult to adjust to. Images can seem distorted and may appear suddenly within the peripheral vision. Distances may be hard to judge.
Sometimes a patient has two cataracts and needs to wear glasses between the first and second operation. They are particularly troublesome during this period. The treated eye will see images magnified while the other eye will view them as they actually are, and the brain cannot blend the two images. This is a temporary state that is resolved by the second operation.
Modern cataract surgery is one of the safest of all surgical procedures. Most complications, even if they occur, are not serious. They can include the following:
- Swelling and inflammation. Risk is about 1%. This complication is particularly harmful for patients with existing uveitis (chronic inflammation in the eye, which can be due to various conditions).
- Glare. Patients may experience glare after surgery from light scattering at the edges of the new lens, particularly with square-edged IOLs, which are typically used with posterior capsular cataracts. In most cases, this is a temporary problem that resolves after a few weeks. Sometimes, the problem lasts, and the patient needs another operation. Some research suggests that texturizing the edges of the square lens can significantly reduce glare.
- Materials used in some lenses trigger an immune response in about half of patients. This causes inflammation and tiny deposits of tissue in the eye that lead to secondary cataracts -- called posterior capsule opacification. Studies suggest that silicone implants pose the highest rates for inflammation and secondary cataracts, particularly in patients with other eye diseases. Newer silicon IOLs pose less risk. In one study, the lowest rates were with IOLs made of acrylic and heparin-coated PMMA.
- Retinal detachment. In rare cases, the retina at the rear of the eye can become detached. Risk is very low (0.1%), and phacoemulsification poses less of a risk for this than standard surgery.
- Atonia (loss of muscle tone that results in a disturbing glare). (Phacoemulsification poses less of a risk than standard surgery.)
- Glaucoma. This is an eye condition in which the pressure of fluids inside the eye rises dangerously. Risk is very low, but patients should be sure to avoid activities after surgery that increase pressure.
- Infection. This is very rare (0.2%), but may be significant if it does develop.
- Blisters on the cornea. There is a higher risk of rupture with phacoemulsification, but the risk is extremely low, particularly for experienced eye surgeons.
- Bleeding can develop inside the eye. Risk is about 1% for minor bleeding and 1 in 10,000 for severe bleeding.
- An implanted IOL can become damaged or dislocated. Risk is very low.
- The surgery itself can produce vision loss or impairment. The risk for this is 1 in 1,000. (Phacoemulsification poses less of a risk than standard surgery.)
Click the icon to see an image of macular degeneration.
Phacoemulsification does have some specific complications, although they are rare, particularly with experienced eye surgeons. They include:
- Rupture of the lens capsule.
- Loss of the lens nucleus into the eye fluid. (This will require removal by a specialist and may result in poorer vision.)
- Flying fragments of the lens can damage the cornea or threaten the retina.
- Pre- and postoperative changes in blood pressure, which are generally not a problem, should be observed carefully, since in some cases the changes may be extreme.
In about 30% of cases patients develop secondary cataracts within 1 - 5 years after either procedure, and therefore these patients need different treatment choices.
Preventing Infection and Reducing Swelling. The ophthalmologist may prescribe the following medications:
- A topical antibiotic may protect against infection.
- Corticosteroid eyedrops or ointments are often used to reduce swelling. Corticosteroids (commonly called steroids) are potent anti-inflammatory drugs. However, they also pose a risk for increased pressure in the eye and infection. Some newer steroids, such as rimexolone, loteprednol, and fluorometholone, may lower the risk for abnormal pressure.
- Nonsteroidal anti-inflammatory drugs (NSAIDs), such as diclofenac, ketorolac, naproxen, and voltaren, also reduce swelling and do not have the same risks as steroids. Newer NSAIDS approved to treat pain and swelling after cataract surgery include bromfenac (Xibrom) and nepafenac (Nevanac).
Factors that Increase Risk for Complications. The risks of complications are greater for the following people:
- Patients who have other eye diseases.
- People with diabetes. Intracapsular and extracapsular cataract extraction are known to pose a high risk for the development or worsening of retinopathy, a known eye complication of diabetes. The amount of experience a surgeon has plays a role in whether or not a patient has this complication.
- People who have taken tamsulosin (Flomax) or other alpha-1 blocker drugs. Tamsulosin is a muscle relaxant prescribed for treatment of several urinary conditions, including benign prostatic hyperplasia (BPH). In 2005, a leading ophthalmologic association and the FDA warned that tamsulosin may cause intraoperative floppy iris syndrome (IFIS), a loss of muscle tone in the iris that can cause complications during eye surgery. Problems have been reported both for patients who were taking the drug during surgery as well as those who had stopped taking the drug weeks or months before surgery. Men who have taken tamsulosin or similar drugs should inform their eye surgeon. The surgeon may need to use different techniques to minimize the risk of IFIS. A 2006 study indicated that patients can have safe and successful surgeries with these modified techniques.
Returning Home and Follow-up Visits.
- Patients usually leave the surgical site within an hour of surgery. Cataract surgery almost never requires an overnight hospital stay.
- Patients need someone to drive them home and stay with them for a few days until their vision acclimates.
- The patient is usually examined the day after surgery and then during the following month. Additional visits occur as necessary.
- Vision usually remains blurred for a while but gradually clears, usually over 2 - 6 weeks. (It can take longer.)
- When the doctor decides the condition has stabilized, the patient will receive a final prescription for glasses or contacts.
Protecting the Eye. Postoperative protection of the eye typically involves:
- The ophthalmologist usually tapes a bandage over the eye to protect it during the healing process.
- When changing the bandage, the eye can be cleaned gently using a washcloth dipped in warm water without soap. A new bandage can then be positioned and taped.
- It is very important not to press or rub the eye during this procedure.
- An eye shield may be placed over the bandage at night.
Avoiding Glaucoma. Cataract surgery can cause glaucoma, a condition in which the pressure of fluids inside the eye rises dangerously. It is very important to minimize any activity that increases internal eye pressure. Postoperative cataract patients take the following precautions:
- Minimize vigorous exercise.
- Put on shoes while sitting and without lifting up the feet.
- Kneel instead of bending over to pick something up.
- Avoid lifting.
- Limit reading since it requires eye movement (watching television is all right).
- Sleep on the back or on the unoperated side.
Cataracts and Glaucoma. For patients with both glaucoma and cataracts, experts recommend:
- In patients with cataracts and poorly controlled glaucoma, a two-step procedure for both eye conditions may be used. The patient first receives a trabeculectomy for glaucoma, followed by cataract surgery. Fluid leakage and the presence of blood in the back chamber of the eye are potential complications of this combined procedure. Phacoemulsification has improved success rates and reduced high complication rates of the double procedure compared with extracapsular cataract extraction. New advances that replace trabeculectomy with nonpenetrating glaucoma surgery may prove to be beneficial.
- In patients who have cataracts plus either closed-angle glaucoma or open angle glaucoma that is stabilized with medication, the cataract may be extracted and medication continued for the glaucoma.
Cataracts and Corneal Disease. Patients with both cataracts and corneal disease may have one of the following procedures:
- Combination Procedure. A single operation that combines three procedures. The combined procedure has been used since the late 1970s and employs extracapsular cataract extraction and intraocular lens insertion with corneal transplantation (called penetrating keratoplasty).
- Sequential Procedure. An operation that uses two procedures sequentially. The sequential option performs the cataract procedures and the corneal transplantation separately.
Recovery of vision is usually much more rapid after the combined procedure than after the sequential procedure. Performing the procedures sequentially may also carry a higher rejection rate of the implant.
In any case, many experts recommend that for most patients the sequential procedures may be the better option because it appears to have fewer of the following complications than with the combined procedure:
- Posterior capsule rupture
- Eye fluid loss
- Postoperative refractive errors, which result in abnormal distribution of light patterns
The rate of these errors still depends on the skill of the surgeon and the power of the implanted lens no matter what approach is used.
About 30% of patients who have extracapsular cataract surgery develop a secondary "after-cataract" called posterior capsular opacification. Posterior capsular opacification generally occurs because of the following events:
- After surgery, there are still some natural lens cells left behind that proliferate on the back of the capsule.
- The capsule gradually becomes cloudy and interferes with clear vision the same way the original cataract did.
The probability of developing a secondary cataract may be over one-third by 9 years. The risk is lower with phacoemulsification. Secondary cataracts are more likely to occur in younger patients, in those with diabetes, or when cataract surgery is combined with vitrectomy (clearance of debris from the fluid in the eye).
Preventing Posterior Capsular Opacification. Studies suggest that acrylic lenses have the lowest risk for posterior capsular opacification. A number of substances to prevent posterior capsular opacification are under investigation, including tranilast eyedrops, new lens materials, special capsular rings inserted during phacoemulsification, and new coatings on the implanted lens.
Treatment for Posterior Capsular Opacification. The standard treatment is laser surgery known as a YAG capsulotomy. (Capsulotomy means cutting into the capsule, and YAG is an abbreviation of yttrium aluminum garnet, the laser most often used for this procedure.)
- This is an outpatient procedure and involves no incision.
- Using the laser beam, the ophthalmologist makes an opening in the clouded capsule to let light through.
- After the procedure the patient should remain in the doctor's office for an hour to be sure that pressure in the eye is not elevated.
- An eye examination for any complications should follow within 2 weeks.
Complications. Laser surgery has become so commonplace that some ophthalmologists use it after cataract surgery to prevent later clouding. However, laser surgery has its own risks and possible complications, similar to those of cataract surgery itself, and can also lead to poorer vision or blindness. About 1% of laser surgery patients develop a detached retina, a risk is much higher than the original cataract surgery.
Click the icon to see an image of a detached retina.
In some people, particularly those with glaucoma or who are severely nearsighted, the pressure in the eye may spike after laser surgery. Certain drugs used for treating glaucoma, such as dorzolamide (Trusopt) or apraclonidine (Iopidine), may help prevent this occurrence. It is strongly recommended, however, that this surgery be performed only if the lens capsule clouds up again, not to prevent a secondary cataract.
Infants. Treatment of infants first depends on whether one or both eyes are affected:
- For infants born with cataracts in one eye, the American Academy of Ophthalmology recommends surgery as soon as possible, by 4 months or ideally even earlier. The procedure is followed by contact lens correction and patching of the unaffected eye. Although this approach is successful in many cases, some children still become blind in the affected eye. There is also a high risk for glaucoma after surgery.
- In infants with cataracts in both eyes, surgery is not always an option. Sometimes surgery may be performed sequentially, with the second eye operated on a few days after the first. Phacoemulsification appears to pose a much higher risk for secondary cataracts than standard lens removal.
Toddlers and Older Children. Intraocular lens replacement is now becoming standard treatment for children 2 years and older.
Resources
- www.ascrs.org -- The American Society of Cataract and Refractive Surgery
- www.aao.org -- American Academy of Ophthalmology
- www.nei.nih.gov -- National Eye Institute
- www.eyesurgeryeducation.com -- Eye Surgery Education Council
- www.lighthouse.org -- Lighthouse International
- www.aao.org/aao/find_eyemd.cfm -- Find an ophthalmologist
References
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Clinical Trial of Nutritional Supplements and Age-Related Cataract Study Group, Maraini G, Sperduto RD, Ferris F, Clemons TE, Rosmini F, et al. A randomized, double-masked, placebo-controlled clinical trial of multivitamin supplementation for age-related lens opacities. Clinical trial of nutritional supplements and age-related cataract report no. 3. Ophthalmology. 2008 Apr;115(4):599-607.e1.
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Long V, Chen S, Hatt S. Surgical interventions for bilateral congenital cataract. Cochrane Database Syst Rev. 2006 Jul 19;3:CD003171.
Moeller SM, Voland R, Tinker L, Blodi BA, Klein ML, Gehrs KM, et al. Associations between age-related nuclear cataract and lutein and zeaxanthin inthe diet and serum in the Carotenoids in the Age-Related Eye Disease Study, an Ancillary Study of the Women's Health Initiative. Arch Ophthalmol. 2008 Mar;126(3):354-64.
Olitsky SE, Hug D, and Smith LP. Abnormalities of the lens. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. St. Louis, MO: WB Saunders; 2007; chap 627.
Rein DB, Zhang P, Wirth KE, Lee PP, Hoerger TJ, McCall N, et al. The economic burden of major adult visual disorders in the United States. Arch Ophthalmol. 2006 Dec;124(12):1754-60.
Wishart MS, Dagres E. Seven-year follow-up of combined cataract extraction and viscocanalostomy. J Cataract Refract Surg. 2006 Dec;32(12):2043-9.
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
