Cataracts are a common age-related vision problem that involves clouding of the lens in the eye. Cataracts are responsible for about one half of the world's blindness. Developing countries bear the brunt of blindness caused by cataract, due to higher incidence, lower age at onset, and less access to eye care compared to developed countries. In the United States, about 24 million people age 40 and older have cataracts. The older a person gets, the greater the risk of developing cataracts. Women are more likely to develop cataracts than men.
In addition to age, other factors may increase the risk for cataract development. These include:
During the early stages, cataracts may have little effect on vision. Symptoms vary due to the type of cataract (nuclear, cortical, or posterior subcapsular.) Depending on the type and extent of the cataract, people may experience the following symptoms:
Cataracts never go away on their own, but some stop progressing after a certain point. If cataracts continue to progress, they can cause blindness if left untreated. Fortunately, cataracts can almost always be successfully treated with surgery. Millions of cataract operations are performed each year in the United States, and there is a very low risk for complications. However, before opting for surgery, people need to consider on an individual basis how severely a cataract interferes with their quality of life. Cataract surgery is rarely an emergency, so people 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 is generally painless, takes less than 1 hour and is performed on an outpatient basis. Most people remain awake, but sedated, during the procedure. If you have cataracts in both eyes, doctors recommend waiting at least 1 to 2 weeks between surgeries.
A cataract is an opacity, or clouding, of the lens of the eye.
The lens is normally clear. If the lens becomes cloudy or is opacified, it is called a cataract.
How Cataracts Form
The likelihood of developing cataracts increases with age. Cataracts typically develop in the following way:
Some cataracts stop progressing after a certain point, but they never go away on their own. 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. Fortunately, cataracts can nearly always be successfully removed with surgery, greatly improving vision.
Types of Cataracts
Cataracts can form in any of three parts of the lens and are named by their location:
Most cataracts are due to age, but there are other causes as well. Doctors categorize cataracts based on their cause:
Aging is the most common cause of cataracts. Cumulative effects of exposure to sunlight, irradiation, toxins, drugs, and disease cause the modification of proteins in the lens that makes them clump together. One of the causes of lens protein modifications is oxidative stress.
Oxidative stress is an imbalance between oxidants and antioxidants:
One theory is that in the aging eye, barriers develop that prevent glutathione and other protective antioxidants from reaching the nucleus in the lens, thus making it vulnerable to oxidation.
Secondary cataracts refer to cataracts that result from another medical condition or medical treatment. Causes of secondary cataracts include:
Cataracts can develop from overexposure to radiation, including sunlight. A common cause of radiation cataracts is the ionizing radiation used during treatment for head and neck cancer. Cataracts are also a side effect of total body radiation treatments, which are administered for certain cancers.
Traumatic cataracts are caused by blunt or penetrating injury to the eye. This type of cataract can develop immediately after the injury or many years later.
In rare cases, a baby is born with cataracts or develops them during infancy. Causes of congenital cataracts include:
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. Some people develop cataracts during their middle-aged years (40s and 50s), but these cataracts tend to be very small. It is after age 60 that cataracts are most likely to affect vision. Nearly one half of people age 75 and older have cataracts.
Women face a higher risk than men.
Cataracts tend to run in families.
Race and Ethnicity
In the United States, several prevalence studies have shown that cataracts are more likely to be a cause of vision impairment in blacks than in whites. This may be due to limited access to health care among non-white populations.
Medical Conditions and Treatments
Certain medical conditions and treatments increase the risk for cataracts:
Excessive exposure to ultraviolet B (UVB) radiation from sunlight increases the risk for cataracts. The risk may be highest among those who have significant sun exposure at a young age. People whose jobs expose them to sunlight for prolonged periods are also at increased risk.
Sunglasses or a wide-brimmed hat can help block the harmful effects of ultraviolet (UV) radiation. Protective sunglasses do not have to be expensive but it is important that they block 99% to 100% of UV light. Polarized, mirror-coated, or blue light-blocking lenses do not protect against UV radiation.
Smoking a pack of cigarettes every day doubles the risk of developing cataracts. Smokers are at particular risk for cataracts located in the nuclear portion of the lens. Quitting smoking can help reduce the risk, although the risk will remain higher in former smokers than those who never smoked.
Chronic heavy drinkers are at high risk for a number of eye disorders, including cataracts.
Although it is not clear how much of a role nutrition plays in age-related cataracts, there is evidence that antioxidant-rich fruits and vegetables may offer some protection. The antioxidants most studied for cataract prevention are lutein and zeaxanthin, which are a type of antioxidants called carotenoids. Lutein and zeaxanthin are found in the lens.
Some research suggests that foods that contain these carotenoids, such as green leafy vegetables, may help slow the aging process in the eye and protect against cataracts. However, studies indicate that dietary supplements that contain lutein and zeaxanthin, or antioxidant vitamins, such as vitamin C or E, do not reduce the risks for cataract formation.
Antioxidants found in food, not supplements, appear to offer the best protection. Kale, collard greens, and spinach are the main food sources for lutein and zeaxanthin.
During the early stages, cataracts have little effect on vision. People who have small cataracts can often see well enough around the clouded areas to function normally. But as a cataract grows larger and increasingly clouds the lens, it can interfere greatly with daily activities such as reading and driving.
As a cataract progresses, symptoms may include:
This photograph shows a cloudy white lens (cataract) seen through the pupil. Cataracts are a leading cause of decreased vision in older individuals, but children may have congenital cataracts. With new surgical techniques, the cataract can be removed, a new lens implanted, and the person can usually return home the same day.
Either an ophthalmologist or an optometrist can examine people for cataracts, but only ophthalmologists are qualified to treat cataracts.
The main tests used by an eye care professional to diagnose cataracts are:
All of these tests are quick and painless.
Visual Acuity Tests
Visual acuity tests evaluate how clearly a person can see. The Snellen eye chart is often used, with rows of letters decreasing in size:
The visual acuity test can be performed in many different ways. It is a quick way to detect vision problems and is frequently used in schools or for mass screening.
Ophthalmoscopy is performed to examine the back part of the eye (fundus), which includes the retina, optic nerve, and blood vessels. This test can help detect cataracts as well as other eye diseases such as glaucoma. The eye doctor may give you eye drops before the test to dilate (widen) the pupils of your eyes.
There are several ways that ophthalmoscopy can be performed:
Tonometry measures the pressure inside your eye. It is used to find out if glaucoma is contributing to your symptoms, although glaucoma rarely causes visual symptoms unless it is advanced. The clinician will first give you anesthetic drops to numb your eye. Next, a small device is gently pressed against your eye to measure intra-ocular (inside the eye) pressure. Eye pressure may also be evaluated in different ways such as with a hand-held electronic device or a gentle puff of air to indent the eye.
Other tests that may be used to diagnose cataracts or to determine if surgery is needed include:
Surgery is the only cure for cataracts, but it is often not an emergency. Most cataracts cause no other health problems besides reducing a person's ability to see. Usually, there is no harm in reasonably delaying surgery, except for an increased risk of injury from falls or unsafe driving. Sometimes delaying surgery will cause a moderate (easy to perform surgery on) cataract to progress to an advanced (difficult to perform surgery on) cataract. The risks of surgical complications can be increased in advanced cataract. People usually have plenty of time to carefully consider options and discuss them with an ophthalmologist.
There is no constant rate at which cataracts progress:
The following measures may help manage early cataracts:
Choosing Cataract Surgery
Cataract removal is one of the most common types of eye surgery performed in the United States, especially for people over age 65. In the past, with older techniques, cataract surgery was not performed until the cataract had become well developed (ripe.) Newer techniques, however, have made it safer and even more efficient to operate in earlier stages. Cataract surgery improves vision in up to 95% of people and prevents millions of people from going blind. Femtosecond laser technology has also become a commonly utilized technology to complete part of the cataract surgery.
In general, after cataracts are diagnosed, the decision to remove them should be based on the person's own perception of vision difficulties and the effect of vision loss on normal activity or independent living. However, since progression is often gradual and subtle, it may not be apparent how they have affected vision and activities of daily life. Those considering cataract surgery should be made fully aware of all the potential risks and benefits of surgery.
Questions for the Ophthalmologist
You should ask the ophthalmologist the following questions before deciding to have cataract surgery:
If you have further questions or doubts about the procedure, you may want to get a second opinion from another ophthalmologist.
Treatment for People with Accompanying Eye Conditions
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. In general, surgery for a second cataract is usually performed at least 1 to 2 weeks after surgery for the first eye. Although uncommon, in some circumstances surgery may be performed on both eyes at the same time.
Cataracts and Glaucoma
There are various approaches to treating people who have both cataracts and glaucoma. Your doctor will recommend an approach based on your individual condition. Some options include:
Treating Cataracts in Children
Treatment of infants first depends on whether one or both eyes are affected:
Toddlers and Older Children
Intraocular lens replacement is now standard treatment for children age 2 years and older.
Preparing for Cataract Surgery
Cataract surgery is usually done as an outpatient procedure under local anesthesia and takes less than an hour. Preoperative preparations may include:
All cataract procedures involve removal of the lens (cataract extraction) and replacing it with an artificial lens called intraocular lens (IOL). Cataract extraction is performed by one of three procedures:
Anesthesia for Cataract Surgery
There are three methods of providing anesthesia for cataract surgery. Depending on the surgery and the patient, one or more of these techniques may be used:
Topical anesthesia involves topical drops that numb the surface of the eye, and a tiny amount of anesthetic that is injected directly into the eye at the beginning of the actual surgery. Nothing specifically blocks the nerves of the muscles that move the eye. Sedation in the form of an injection through a vein or occasionally as a pill, will help the patient hold the eye still.
In local anesthesia, a sedative injection through a vein is given, followed by injections of anesthetic around the eye to numb the eye and block the nerves to the eye muscles.
General anesthesia is the method of choice for babies, children, and adults who are not able to cooperate.
Phacoemulsification (phaco means lens; emulsification means to liquefy) is the most common cataract removal method in the United States.
The procedure generally involves the following:
Most phacoemulsification procedures take about 15 minutes, and the patient is usually out of the operating room in under an hour. There is little discomfort afterward, and complete visual recovery usually occurs within 1 to 5 days.
Phacoemulsification is sometimes combined with glaucoma surgical procedures, for people who have both glaucoma and cataracts.
Extracapsular Cataract Extraction
Extracapsular cataract extraction, the precursor to phacoemulsification, is now generally used only in people who have an extremely hard lens.
The procedure generally involves the following:
Laser Cataract Surgery
Newer technologies have been developed so that the incisions used in cataract surgery can be made with a femtosecond laser rather than a blade. (The femtosecond laser was originally developed to make the flap in LASIK surgery. It has since been modified to be useful in cataract surgery.) Femtosecond laser also performs a crucial step of cataract surgery called capsulorhexis (making a circular opening of the front membrane of the cataract.) The laser can also soften the lens nucleus so that phacoemulsification will be easier. It still remains to be seen whether laser cataract surgery presents clear advantages over more conventional methods.
Regardless of which technique is used to remove the cataract, a lens implant (IOL) is almost always inserted to correct the optics of the eye, which now has no natural lens.
Replacement Lenses and Glasses
With the clouded lens removed, the eye cannot focus a sharp image on the retina and is functionally blind at all distances. A replacement lens is therefore needed.
Intraocular Lenses (IOLs). An artificial lens, known as an intraocular lens (IOL), is usually inserted immediately after the cataract is extracted. Most IOLs are made out of acrylic, although other materials, such as silicon, are also used.
IOLs are designed to improve specific aspects of vision. In the United States, there are currently 4 choices:
The patient and the doctor must choose the IOL based on specific visual needs. Many people also need eyeglasses after cataract surgery for reading or to correct astigmatism.
Complications of Cataract Surgery
Cataract surgery is one of the safest of all surgical procedures. Most complications are not serious. They can include:
This is suspected when the eye pressure is elevated. If this occurs after cataract surgery, it is usually one of three forms:
Glaucoma is a disorder of the optic nerve that is usually marked by increased fluid pressure inside the eye. The increased pressure causes compression of the retina and the optic nerve which can eventually lead to nerve damage. Without treatment, glaucoma can cause partial vision loss, with blindness as a possible eventual outcome.
Factors that Increase Risk for Complications
The risks of complications are greater if you have:
Preventing Infection and Reducing Swelling
Returning Home and Follow-up Visits:
Protecting the Eye
Postoperative protection of the eye typically involves the following actions:
Other postoperative advice includes:
Treatment of Posterior Capsular Opacification (Secondary or "After Cataract")
About 15% of people who have cataract surgery develop a secondary or "after-cataract" called posterior capsular opacification. Posterior capsular opacification is a clouding of the lens capsule that was intentionally left behind, (it is used to hold the IOL in place) when the original cataract was removed. It generally occurs because some cells of the natural lens remain after surgery and can regrow onto the capsule.
The standard treatment for posterior capsular opacification is a type of laser surgery known as a YAG capsulotomy. (Capsulotomy means making an opening in the capsule, and YAG is an abbreviation of yttrium aluminum garnet, the laser most often used for this procedure.) This is an outpatient procedure that involves no incision and can help improve vision and reduce glare.
YAG capsulotomy involves the following:
YAG laser capsulotomy is generally a safe procedure. Serious complications are rare, but can include retinal detachment.
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