Cataracts

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WHAT ARE CATARACTS?

• 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 photosensitive 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-forties, 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, and the need for reading glasses in almost everyone as they age.
  
  
• In some people, the proteins in the lens may also clump together, forming cloudy ( opaque) areas called cataracts. They usually develop slowly over several years, although in some cases 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.

• Nuclear cataracts. They 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 and people taking steroids.

WHAT CAUSES CATARACTS?

• Oxygen free radicals (also called oxidants) are unstable molecules produced by natural chemical processes in the body.
  
  
• Because oxidants are missing an electron, they tend to bind with other molecules in the body.
  
  
• Toxins, smoking, ultraviolet radiation, infections, and many other factors can create reactions that produce excessive amounts of these oxygen free radicals.
  
  
• In such cases, overproduction can set off a chemical chain reaction that damages any type of cell in the body, including nerve cells in the brain, and even interferes with their DNA.
  
  
• Cataract formation is one of many of their destructive changes.

• UVA radiation is composed of longer wavelengths. They penetrate more deeply and efficiently into the inner skin layers and are responsible for tanning and allergic reactions to sunlight (such as from medication). The main damaging effect of UVA appears to be the promotion of the release of oxidants.
  
  
• UVB radiation produces the shorter wavelength, and primarily affects the outer skin layers. It is the primary cause of sunburn. Long-term exposure to even low levels of UVB radiation, however, can eventually cause changes in the lens, including pigment changes, that contribute to cataract development. (UVB also appears to be responsible for macular degeneration, an aging-related disorder of the retina.)

• Studies, including one in 2000, have reported no increased risk of cataracts among users of nasal-spray corticosteroids used for allergic rhinitis.
  
  
• A number of studies have suggested, however, that adults who use inhaled corticosteroids, such as those for asthma, have a higher risk for cataracts than those who never used inhaled steroids. The higher the dose and longer the duration of use, the greater the risk. In children, cataracts are rare, and the benefits of inhaled steroids for asthma far outweigh any small additional risk.

• Psoralens, a class of drugs used along with light therapy to treat skin disorders, such as psoriasis, can cause cataracts.
  
  
• Allopurinol, a drug used for gout, may increase risk for cataracts, but studies are mixed.
  
  
• The role of long-term aspirin use is unclear. Some research has indicated that aspirin may have protective properties against cataracts, but two large studies found no benefit, and another indicated that long-term use may even promote cataracts.
  
  
• Other drugs associated with cataracts include tamoxifen, phenothiazines, amiodarone, and mepacrine.

• Glaucoma and its treatments (highly associated with cataracts).
  
  
• Diabetes. Cataracts in diabetics appear to form when high levels of blood sugar react with proteins in the eye and begin to form byproducts that accumulate in the lens (sugar cataracts).
  
  
• Hypertension.
  
  
• Rheumatoid arthritis and other connective tissue diseases.

• Physical injury to the eye (such as a hard blow, cut, or puncture).
  
  
• Prolonged exposure to intense heat or cold.
  
  
• Chemical burns.

• Infection during pregnancy.
  
  
• Inherited disorder.
  
  
• Pregnant women who abuse alcohol or drugs increase the risk for cataracts (along with other more serious birth defects) in their infants.

WHAT ARE THE SYMPTOMS OF CATARACTS?

• 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.

• The increasing opacity of the nucleus causes hazy distance vision and increasing glare.
  
  
• Nuclear cataracts often cause progressive near-sightedness 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. This 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.

• These cataracts have little initial effect on vision.
  
  
• As these cataracts grow more opaque and approach the center of the lens, glare usually develops.
  
  
• As these cataracts progress, individuals may experience problems with distance vision, contrast sensitivity, and clarity.

• These cataracts may interfere with near vision, such as reading, and produce glare.
  
  
• They often advance rapidly. For many patients, major impairment of their vision develops in several months.

HOW SERIOUS ARE CATARACTS?

WHAT ARE THE RISK FACTORS FOR CATARACTS?

• People with diabetes or non-diabetes with high glucose levels.
  
  
• People who have indications of kidney damage.
  
  
• People who use steroid medications.

• About 40% of people between 55 and 64 years old had some opaque areas in their lenses, and 5% had fully-developed cataracts.
  
  
• About 70% of people between 65 and 74 years old had opaque areas, and 18% had cataracts.
  
  
• More than 90% of people between 75 and 84 had opaque areas, and almost half had cataracts.

• The closer people live to the equator the greater the chance for cataracts. As suggested by a study in Southern France, sunlight exposure in these climates also increases the risk for severe cortical or mixed cataracts. (In this study, even wearing sunglasses did not reduce the risk for these cataracts, although it did for posterior subcapsular cataracts.)
  
  
• People whose jobs expose them to sunlight for prolonged periods are at higher risk. People in Southern France 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.

• Risk appears to be related to total cumulative smoking, so the sooner you quit the lower your risk.
  
  
• Some smoking-related damage may be reversible.

CAN CATARACTS BE PREVENTED?

• Special purpose, which block 99% of both UVA and UVB rays [ see below ].
  
  
• General purpose, which block 95%.
  
  
• Cosmetic purpose, which block 70%.

• Some experts believe that simple dark-colored sunglasses that block UVB radiation are sufficient to protect against cataracts. Lenses that are dark but not coated with UV-absorbing material, however, 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 the eye.
  
  
• Polarized glasses cut glare but have no effect on UV radiation.
  
  
• Mirror finishes without additional processing also are not fully protective.
  
  
• There is some controversy over whether blue light is harmful to the eyes. Some people, then, prefer amber lenses, which block out the blue spectrum.

• Vitamin C. Evidence for vitamin C is very weak. Studies have reported either no benefits from vitamin C or very modest ones. A 1999 study, for example, reported modest reduction in cataract surgeries in women under 60 years old who took vitamin C for long durations. The study reported no other protective benefits, and no benefits in any other population group. Vitamin C is found in most fruits and vegetables.
  
  
• Vitamin E. A study linked low blood levels of vitamin E to more rapid progression of cataracts in men with high cholesterol levels, and another study measured vitamin levels in blood over a two-year period and found some protective benefits from high levels of vitamin E. Vitamin E is found in avocados, kale, sweet potatoes, vegetable oils, and wheat germ.
  
  
• B vitamins. A study reported that the vitamins B2 (riboflavin) and B3 (niacin) might protect against cataracts that form in the nucleus of the eye, but not in the cortex or in the capsule. Riboflavin plays a critical role in the production of glutathione. The best sources for riboflavin are dairy products, fortified grains, and meat.

HOW ARE CATARACTS DIAGNOSED?

• An ophthalmologist is a physician who specializes in the medical and surgical care of the eye.
  
  
• An optometrist is engaged in the practice of eye care but is not a physician and cannot prescribe medication or perform surgery.

• 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 (the norm).
  
  
• 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.

• To test contrast sensitivity, a chart similar to the Snellen chart is used, on which the letters are the same size but contrast differently with the background.
  
  
• 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 require a number of other pre-operative tests.

• Some people with cataracts perform poorly on the tests yet appear to have no difficulty functioning normally day-to-day.
  
  
• Others perform well on the tests but insist that their eyesight is bad enough to curtail ordinary activities, such as driving.

HOW ARE CATARACTS TREATED?

• Stronger eyeglasses or contact lenses.
  
  
• Use of a magnifying glass during reading.
  
  
• Strong lighting.
  
  
• Medication that dilates the pupil. (May help some people with capsular cataracts, although glare might be a problem with this treatment.)

• Nearly all patients enjoy better vision after surgery. (Patients with significant eye disease, such as glaucoma or corneal or retinal disease, may not experience the same degree of improvement.)
  
  
• Many elderly people experience significant improvement not only in vision but in quality of life after the operation.
  
  
• Some studies indicate that better vision might even help slow down age-related health problems unrelated to the eyes.

• Some develop to a certain point and then stop.
  
  
• Even if a cataract does progress, it may be years before it interferes with vision.
  
  
• Only in a very few, very rare circumstances is it necessary that cataract surgery be performed immediately.

• The Snellen eye test reports 20/40 or worse, with the cataract being responsible for vision loss and glasses or visual aids no longer being helpful.
  
  
• Everyday activities have become difficult to perform and independence is threatened.
  
  
• The patient is at risk for falling in low light.

• Even if the criteria for surgery are met, a very sick, very elderly person in a nursing home may have less need for sharp vision than an active younger adult.
  
  
• 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 physician may perform cataract surgery in order to have a clear view of the eye.

• Having a general physical examination is important for patients with medical problems but does not seem to be necessary or have any effect on surgical complications for most otherwise-healthy patients.
  
  
• 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 are given a sedative along with a local or topical anesthetic. Some patients may require a general anesthetic, such those who are very anxious, those who are unable to cooperate with the surgeon, and those who are allergic to local anesthetics.

• 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. [ See Replacement Lenses and Glasses, below.]
  
  
• 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. One may be required if a tear or break occurs during the procedure or if an unfoldable lens is inserted that requires a wider incision.

• 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. There are greater risks with this procedure for swelling and retinal detachment.)
  
  
• A replacement lens is then usually inserted. [ See Replacement Lenses and Glasses, below.]
  
  
• A small suture is needed to stitch the incision together.

• Polymethylmethacrylate (PMMA). (Has the longest safety record.)
  
  
• Silicone. (Can be inserted through a smaller incision than other materials.)
  
  
• Acrylic. (Allows a controlled unfolding of the lens.)

• Lenses that address a single fixed focal point. Such lenses are suitable either for reading or for 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. Multifocal lenses are increasingly common. One study reported that more than 80% of patients with multifocal lenses were able to see 20/40 or better without correction.
  
  
• Lenses are now available that will correct astigmatism after cataract surgery.

• Patients who ate extremely near-sighted.
  
  
• Patients with other eye disorders.

• 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.

• Patients usually leave the surgical site within an hour of surgery. Cataract surgery almost never requires an overnight hospital stay.
  
  
• They need to have someone drive them home and stay with them for a few days until their vision is acclimated.
  
  
• The patient is usually examined the day after surgery and then during the following month. Additional visits are made as required.
  
  
• Vision usually remains blurred for a while but gradually clears, usually over a two to six-week period. (It can take longer.)
  
  
• When the physician decides the condition has stabilized, the patient will receive a final prescription for glasses or contacts.

• 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.

• A topical antibiotic (neomycin or, more effectively, gentamicin). This agent protects against infection.
  
  
• Anti-inflammatory eyedrops or ointments to reduce swelling. This agent is usually a corticosteroid (commonly called steroids). Corticosteroids, however, increase the risk for pressure in the eye and infection, and one study reported reduced visual acuity with the use of steroids compared to antibiotics. Some newer steroids such as rimexolone, loteprednol, and fluorometholone have fewer of these risks. Nonsteroidal anti-inflammatory drugs, such as diclofenac, ketorolac, and voltaren, do not pose these risks and may be effective alternatives to steroids.

• 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. Television is all right.
  
  
• Sleep on the back or on the unoperated side.

• Specific Complications. Most complications, even if they occur, are not serious. In rare cases, complications can cause poorer vision than before surgery or even blindness in the operated eye. Extensive additional surgery on the eye may be required. They can include the following:
  
  
• Secondary cataracts (Posterior Capsular Opacification). About 30% of patients who undergo extracapsular cataract surgery develop a secondary "after-cataract"; called posterior capsular opacification . [ See Box Prevention and Treatment for Secondary Cataracts (Posterior Capsular Opacification).]
  
  
• Swelling and inflammation. Steroids are used to prevent this. Risk is about 1%.
  
  
• In rare cases, the retina at the rear of the eye can become detached. Risk is less than 1%. 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 about 1%. Patients should be sure to avoid activities that increase pressure.
  
  
• Infection. Antibiotics can usually prevent this.
  
  
• Macular degeneration. Macular degeneration is a common cause of vision loss in the elderly, in which the retina breaks down. In one five-year study, people who underwent cataract surgery had twice the risk for progression of age-related macular degeneration. Interestingly, another study reported that cataract surgery significantly helped patients who had existing macular degeneration. More research is needed to refute or confirm this finding.
  
  
• Blisters on the cornea. Less than 1%.
  
  
• 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 less than 1%.
  
  
• The surgery itself can produce vision loss or impairment. The risk for this is 1 in 1000. (Phacoemulsification poses less of a risk than standard surgery.)

• 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.

• Patients who have other eye disease.
  
  
• 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. Experts have hoped that phacoemulsification would pose a lower risk, but a 2001 study reported a high percentage (25%) of retinopathy progression after this procedure as well. The experience of the surgeon is critical to reduce the risk for this complication.
  
  
• Those with other serious medical problems, such as heart or respiratory disease or diabetes, for which they may be taking strong medications. Either the diseases or the medications can increase the risks.

• In patients who have cataracts plus either closed-angle glaucoma or open angle glaucoma that is stabilized with medication, the cataract may be able to be extracted and medication continued for the glaucoma.
  
  
• In patients with cataracts and poorly controlled glaucoma, a two-step procedure for both eye conditions is needed. These are typically first trabeculectomy for glaucoma followed by cataract surgery. (Although some studies report better success with phacoemulsification using a foldable lens, a 2001 report found differences in failure rates between phacoemulsification and extracapsular cataract extraction.)

• 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. Recovery of vision is usually much more rapid after the combined procedure than after the sequential procedures.
  
  
• Sequential Procedure. An operation that uses two procedures sequentially. The sequential option performs the cataract procedures and the corneal transplantation separately. Performing the procedures sequentially carries a higher rejection rate of the implant.

• Posterior capsule rupture.
  
  
• Eye fluid loss.
  
  
• Postoperative refractive errors, which result in abnormal distribution of light patterns.

WHERE ELSE CAN HELP BE FOUND FOR CATARACTS?