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`Facts About Cataract | National Eye Institute
`
`Facts About Cataract
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`This information was developed by the National Eye Institute to help patients and their families search
`for general information about cataracts. An eye care professional who has examined the patient’s eyes
`and is familiar with his or her medical history is the best person to answer specific questions.
`
`Cataract Defined
`What is a cataract?
`A cataract is a clouding of the lens in the eye that affects vision. Most cataracts are related to aging.
`Cataracts are very common in older people. By age 80, more than half of all Americans either have a
`cataract or have had cataract surgery.
`
`A cataract can occur in either or both eyes. It cannot spread from one eye to the other.
`What is the lens?
`The lens is a clear part of the eye that helps to focus light,
`or an image, on the retina. The retina is the lightsensitive
`tissue at the back of the eye.
`
`In a normal eye, light passes through the transparent lens
`to the retina. Once it reaches the retina, light is changed
`into nerve signals that are sent to the brain.
`
`The lens must be clear for the retina to receive a sharp
`image. If the lens is cloudy from a cataract, the image you
`see will be blurred.
`Are there other types of cataract?
`Yes. Although most cataracts are related to aging, there are other types of cataract:
`1. Secondary cataract. Cataracts can form after surgery for other eye problems, such as glaucoma.
`Cataracts also can develop in people who have other health problems, such as diabetes.
`Cataracts are sometimes linked to steroid use.
`2. Traumatic cataract. Cataracts can develop after an eye injury, sometimes years later.
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`3. Congenital cataract. Some babies are born with cataracts or develop them in childhood, often in
`both eyes. These cataracts may be so small that they do not affect vision. If they do, the lenses
`may need to be removed.
`4. Radiation cataract. Cataracts can develop after exposure to some types of radiation.
`
`Causes and Risk Factors
`What causes cataracts?
`The lens lies behind the iris and the pupil. It works much like a
`camera lens. It focuses light onto the retina at the back of the
`eye, where an image is recorded. The lens also adjusts the
`eye’s focus, letting us see things clearly both up close and far
`away. The lens is made of mostly water and protein. The
`protein is arranged in a precise way that keeps the lens clear
`and lets light pass through it.
`
`But as we age, some of the protein may clump together and
`start to cloud a small area of the lens. This is a cataract. Over
`time, the cataract may grow larger and cloud more of the lens,
`making it harder to see.
`
`Researchers suspect that there are several causes of
`cataract, such as smoking and diabetes. Or, it may be that the
`protein in the lens just changes from the wear and tear it takes
`over the years.
`How can cataracts affect my vision?
`Agerelated cataracts can affect your vision in two ways:
`
`Normal vision
`
`The same scene as viewed by a
`person with cataract
`
`1. Clumps of protein reduce the sharpness of the image reaching the retina.
`The lens consists mostly of water and protein. When the protein clumps up, it clouds the lens and
`reduces the light that reaches the retina. The clouding may become severe enough to cause
`blurred vision. Most agerelated cataracts develop from protein clumpings.
`
`When a cataract is small, the cloudiness affects only a small part of the lens. You may not notice
`any changes in your vision. Cataracts tend to “grow” slowly, so vision gets worse gradually. Over
`time, the cloudy area in the lens may get larger, and the cataract may increase in size. Seeing
`may become more difficult. Your vision may get duller or blurrier.
`2. The clear lens slowly changes to a yellowish/brownish color, adding a brownish tint to vision.
`As the clear lens slowly colors with age, your vision gradually may acquire a brownish shade. At
`first, the amount of tinting may be small and may not cause a vision problem. Over time,
`increased tinting may make it more difficult to read and perform other routine activities. This
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`gradual change in the amount of tinting does not affect the sharpness of the image transmitted to
`the retina.
`
`If you have advanced lens discoloration, you may not be able to identify blues and purples. You
`may be wearing what you believe to be a pair of black socks, only to find out from friends that you
`are wearing purple socks.
`When are you most likely to have a cataract?
`The term “agerelated” is a little misleading. You don’t have to be a senior citizen to get this type of
`cataract. In fact, people can have an agerelated cataract in their 40s and 50s. But during middle age,
`most cataracts are small and do not affect vision. It is after age 60 that most cataracts steal vision.
`Who is at risk for cataract?
`The risk of cataract increases as you get older. Other risk factors for cataract include:
`
`Certain diseases such as diabetes.
`Personal behavior such as smoking and alcohol use.
`The environment such as prolonged exposure to sunlight.
`What can I do to protect my vision?
`Wearing sunglasses and a hat with a brim to block ultraviolet sunlight may help to delay cataract. If you
`smoke, stop. Researchers also believe good nutrition can help reduce the risk of agerelated cataract.
`They recommend eating green leafy vegetables, fruit, and other foods with antioxidants.
`
`If you are age 60 or older, you should have a comprehensive dilated eye exam at least once every two
`years. In addition to cataract, your eye care professional can check for signs of agerelated macular
`degeneration, glaucoma, and other vision disorders. Early treatment for many eye diseases may save
`your sight.
`
`Symptoms and Detection
`What are the symptoms of a cataract?
`The most common symptoms of a cataract are:
`
`Cloudy or blurry vision.
`Colors seem faded.
`Glare. Headlights, lamps, or sunlight may appear too bright. A halo may appear around lights.
`Poor night vision.
`Double vision or multiple images in one eye. (This symptom may clear as the cataract
`gets larger.)
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`Frequent prescription changes in your eyeglasses or contact lenses.
`These symptoms also can be a sign of other eye problems. If you have any of these symptoms,
`check with your eye care professional.
`How is a cataract detected?
`Cataract is detected through a comprehensive eye exam that includes:
`1. Visual acuity test. This eye chart test measures how well you see at various distances.
`2. Dilated eye exam. Drops are placed in your eyes to widen, or dilate, the pupils. Your eye care
`professional uses a special magnifying lens to examine your retina and optic nerve for signs of
`damage and other eye problems. After the exam, your closeup vision may remain blurred for
`several hours.
`3. Tonometry. An instrument measures the pressure inside the eye. Numbing drops may be applied
`to your eye for this test.
`
`Your eye care professional also may do other tests to learn more about the structure and health of
`your eye.
`
`Treatment
`How is a cataract treated?
`The symptoms of early cataract may be improved with new eyeglasses, brighter lighting, antiglare
`sunglasses, or magnifying lenses. If these measures do not help, surgery is the only effective treatment.
`Surgery involves removing the cloudy lens and replacing it with an artificial lens.
`
`A cataract needs to be removed only when vision loss interferes with your everyday activities, such as
`driving, reading, or watching TV. You and your eye care professional can make this decision together.
`Once you understand the benefits and risks of surgery, you can make an informed decision about
`whether cataract surgery is right for you. In most cases, delaying cataract surgery will not cause long
`term damage to your eye or make the surgery more difficult. You do not have to rush into surgery.
`
`Sometimes a cataract should be removed even if it does not cause problems with your vision. For
`example, a cataract should be removed if it prevents examination or treatment of another eye problem,
`such as agerelated macular degeneration or diabetic retinopathy. If your eye care professional finds a
`cataract, you may not need cataract surgery for several years. In fact, you might never need cataract
`surgery. By having your vision tested regularly, you and your eye care professional can discuss if and
`when you might need treatment.
`
`If you choose surgery, your eye care professional may refer you to a specialist to remove the cataract.
`
`If you have cataracts in both eyes that require surgery, the surgery will be performed on each eye at
`separate times, usually four to eight weeks apart.
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`Many people who need cataract surgery also have other eye conditions, such as agerelated macular
`degeneration or glaucoma. If you have other eye conditions in addition to cataract, talk with your doctor.
`Learn about the risks, benefits, alternatives, and expected results of cataract surgery.
`What are the different types of cataract surgery?
`There are two types of cataract surgery. Your doctor can explain the differences and help determine
`which is better for you:
`1. Phacoemulsification, or phaco. A small incision is made on the side of the cornea, the clear,
`domeshaped surface that covers the front of the eye. Your doctor inserts a tiny probe into the
`eye. This device emits ultrasound waves that soften and break up the lens so that it can be
`removed by suction. Most cataract surgery today is done by phacoemulsification, also called
`“small incision cataract surgery.”
`2. Extracapsular surgery. Your doctor makes a longer incision on the side of the cornea and
`removes the cloudy core of the lens in one piece. The rest of the lens is removed by suction.
`
`After the natural lens has been removed, it often is replaced by an artificial lens, called an intraocular
`lens (IOL). An IOL is a clear, plastic lens that requires no care and becomes a permanent part of your
`eye. Light is focused clearly by the IOL onto the retina, improving your vision. You will not feel or see the
`new lens.
`
`Some people cannot have an IOL. They may have another eye disease or have problems during
`surgery. For these patients, a soft contact lens, or glasses that provide high magnification, may
`be suggested.
`What are the risks of cataract surgery?
`As with any surgery, cataract surgery poses risks, such as infection and bleeding. Before cataract
`surgery, your doctor may ask you to temporarily stop taking certain medications that increase the risk of
`bleeding during surgery. After surgery, you must keep your eye clean, wash your hands before touching
`your eye, and use the prescribed medications to help minimize the risk of infection. Serious infection can
`result in loss of vision.
`
`Cataract surgery slightly increases your risk of retinal detachment. Other eye disorders, such as high
`myopia (nearsightedness), can further increase your risk of retinal detachment after cataract surgery.
`One sign of a retinal detachment is a sudden increase in flashes or floaters. Floaters are little “cobwebs”
`or specks that seem to float about in your field of vision. If you notice a sudden increase in floaters or
`flashes, see an eye care professional immediately. A retinal detachment is a medical emergency. If
`necessary, go to an emergency service or hospital. Your eye must be examined by an eye surgeon as
`soon as possible. A retinal detachment causes no pain. Early treatment for retinal detachment often can
`prevent permanent loss of vision. The sooner you get treatment, the more likely you will regain good
`vision. Even if you are treated promptly, some vision may be lost.
`
`Talk to your eye care professional about these risks. Make sure cataract surgery is right for you.
`Is cataract surgery effective?
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`Is cataract surgery effective?
`Cataract removal is one of the most common operations performed in the United States. It also is one of
`the safest and most effective types of surgery. In about 90 percent of cases, people who have cataract
`surgery have better vision afterward.
`What happens before surgery?
`A week or two before surgery, your doctor will do some tests. These tests may include measuring the
`curve of the cornea and the size and shape of your eye. This information helps your doctor choose the
`right type of IOL.
`
`You may be asked not to eat or drink anything 12 hours before your surgery.
`What happens during surgery?
`At the hospital or eye clinic, drops will be put into your eye to dilate the pupil. The area around your eye
`will be washed and cleansed.
`
`The operation usually lasts less than one hour and is almost painless. Many people choose to stay
`awake during surgery. Others may need to be put to sleep for a short time.
`
`If you are awake, you will have an anesthetic to numb the nerves in and around your eye.
`
`After the operation, a patch may be placed over your eye. You will rest for a while. Your medical team
`will watch for any problems, such as bleeding. Most people who have cataract surgery can go home the
`same day. You will need someone to drive you home.
`What happens after surgery?
`Itching and mild discomfort are normal after cataract surgery. Some fluid discharge is also common.
`Your eye may be sensitive to light and touch. If you have discomfort, your doctor can suggest treatment.
`After one or two days, moderate discomfort should disappear.
`
`For a few days after surgery, your doctor may ask you to use eyedrops to help healing and decrease the
`risk of infection. Ask your doctor about how to use your eyedrops, how often to use them, and what
`effects they can have. You will need to wear an eye shield or eyeglasses to help protect your eye. Avoid
`rubbing or pressing on your eye.
`
`When you are home, try not to bend from the waist to pick up objects on the floor. Do not lift any heavy
`objects. You can walk, climb stairs, and do light household chores.
`
`In most cases, healing will be complete within eight weeks. Your doctor will schedule exams to check on
`your progress.
`Can problems develop after surgery?
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`Problems after surgery are rare, but they can occur. These problems can include infection, bleeding,
`inflammation (pain, redness, swelling), loss of vision, double vision, and high or low eye pressure. With
`prompt medical attention, these problems can usually be treated successfully.
`
`Sometimes the eye tissue that encloses the IOL becomes cloudy and may blur your vision. This
`condition is called an aftercataract. An aftercataract can develop months or years after
`cataract surgery.
`
`An aftercataract is treated with a laser. Your doctor uses a laser to make a tiny hole in the eye tissue
`behind the lens to let light pass through. This outpatient procedure is called a YAG laser capsulotomy. It
`is painless and rarely results in increased eye pressure or other eye problems. As a precaution, your
`doctor may give you eyedrops to lower your eye pressure before or after the procedure.
`When will my vision be normal again?
`You can return quickly to many everyday activities, but your vision may be blurry. The healing eye needs
`time to adjust so that it can focus properly with the other eye, especially if the other eye has a cataract.
`Ask your doctor when you can resume driving.
`
`If you received an IOL, you may notice that colors are very bright. The IOL is clear, unlike your natural
`lens that may have had a yellowish/brownish tint. Within a few months after receiving an IOL, you will
`become used to improved color vision. Also, when your eye heals, you may need new glasses or
`contact lenses.
`What can I do if I already have lost some vision
`from cataract?
`If you have lost some sight from cataract or cataract surgery, ask your eye care professional about low
`vision services and devices that may help you make the most of your remaining vision. Ask for a referral
`to a specialist in low vision. Many community organizations and agencies offer information about low
`vision counseling, training, and other special services for people with visual impairments. A nearby
`school of medicine or optometry may provide low vision services.
`
`Current Research
`What research is being done?
`The National Eye Institute is conducting and supporting a number of studies focusing on factors
`associated with the development of agerelated cataract. These studies include:
`
`The effect of sunlight exposure, which may be associated with an increased risk of cataract.
`Vitamin supplements, which have shown varying results in delaying the progression of cataract.
`Genetic studies, which show promise for better understanding cataract development.
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`This online resource guide provides information about cataracts. It answers questions about causes and
`symptoms, and discusses diagnosis and types of treatment. It was adapted from Don’t Lose Sight of
`Cataract (NIH Publication No. 943463) and Cataract: What You Should Know (NIH Publication No. 03
`201).
`
`Last Reviewed: September 2009
`
`The National Eye Institute (NEI) is part of the National Institutes of Health (NIH) and is the Federal
`government’s lead agency for vision research that leads to sightsaving treatments and plays a key role
`in reducing visual impairment and blindness.
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