What Are Cataracts?

A cataract is a clouding of the normally clear lens of your eye. The Latin word cataracta means "waterfall" — imagine trying to peer through a sheet of falling water or through a frosty or fogged-up window. Clouded vision can make it more difficult to read, drive a car or see the expression on your friend's face. Cataracts commonly affect distance vision and cause problems with glare. They generally don't cause pain, double vision with both eyes or abnormal tearing.

The most common type of cataract is related to aging. Clouding of the lens is a normal part of getting older, sort of like gray hair or wrinkles. Almost all Americans age 65 and older have some degree of clouding of the lens. Most cataracts develop slowly and don't disturb your eyesight early on. But as the clouding progresses, the cataract eventually interferes with your clear vision.

The key to living with cataracts is knowing when it's time not to live with them any longer. In the early stages, stronger lighting and eyeglasses can help you deal with the vision problems. But at a certain point, if your normal lifestyle is jeopardized by impaired vision, you might need surgery. Thanks to enormous advances in the management of this condition, cataract removal is one of the safest, most effective and most common surgical procedures — one that restores the sight of millions of Americans.

Signs and Symptoms

A cataract usually develops slowly and causes no pain. At first the cloudiness may affect only a small part of the lens, and you may be unaware of any vision loss. Over time, however, as the cataract grows larger, it clouds more of your lens. When significantly less light reaches the retina, your vision becomes impaired.

Symptoms of a cataract include:

• Clouded, blurred or dim vision
  
  
• Increasing difficulty with vision at night
  
  
• Sensitivity to light and glare
  
  
• Halos around lights
  
  
• The need for brighter light for reading and other activities
  
  
• Frequent changes in eyeglass or contact lens prescriptions
  
  
• Fading or yellowing of colors
  
  
• Double vision or multiple vision in one eye

If you have a cataract, light from the sun, lamps or oncoming headlights may seem too bright. Glare and halos around lights can make driving uncomfortable and dangerous. You may experience eyestrain or find yourself blinking more often to clear your vision.

Cataracts don't typically cause any change in the appearance of your eye or the production of tears. Pain, redness, itching, irritation, aching in your eye or a discharge from your eye may be signs and symptoms of other eye disorders.

A cataract isn't dangerous to the physical health of your eye unless the cataract becomes completely white, a condition known as an overripe (hypermature) cataract. This can cause inflammation, pain and headache. A hypermature cataract is extremely rare, and you need to have it removed quickly.

Causes

A cataract can develop in one or both eyes, and it may or may not affect the entire lens. The lens is located just behind the iris and the pupil. It's shaped like a magnifying glass — thicker in the middle and thinner near the edges. Tiny ligaments, which are bands of tough tissue fiber, hold it in place.

When your eyes work properly, light passes through the cornea and the pupil to the lens. The lens focuses this light, producing clear, sharp images on the retina, the light-sensitive membrane on the back inside wall of your eyeball that functions like the film of a camera. The clouding of the lens, or cataract, scatters the light and prevents a sharply defined image from reaching the retina. Your vision becomes blurred.

The lens consists of three layers. The outer layer (capsule) is a thin, clear membrane. It surrounds a soft, clear material (cortex). The hard center of the lens is the nucleus. If you think of the lens as a piece of fruit, the capsule is the skin, the cortex is the fleshy fruit, and the nucleus is the pit. A cataract can form in any part of the lens.

Cataracts occur in three types:

• Nuclear. A nuclear cataract is the most common type of cataract and the one most associated with aging. It occurs in the center of the lens. In its early stages, as the lens changes the way it focuses light, you may become more nearsighted or even experience a temporary improvement in your reading vision. Some people actually stop needing their glasses. Unfortunately, this so-called second sight disappears as the lens gradually turns yellow or greenish and begins to cloud vision. As the cataract progresses, the lens may even turn brown. You may have particular problems seeing in dim light and find driving at night especially troublesome.
  
  
• Cortical. A cortical cataract begins as whitish, wedge-shaped streaks on the outer edge of the lens cortex. As it slowly progresses, the streaks extend to the center and interfere with light passing through the nucleus. Both your distance and near vision can be impaired. Focusing problems and distortion are common. You may also have problems with glare and loss of contrast. Many people with diabetes develop cortical cataracts. Cortical cataracts are the only type of cataract associated with exposure to ultraviolet (UV) light.
  
  
• Subcapsular. A subcapsular cataract starts as a small, opaque area just under the capsule shell. It usually forms at the back of the lens, right in the path of light on its way to the retina. This type of cataract may occur in both eyes but tends to be more advanced in one eye than the other. A subcapsular cataract often interferes with your reading vision, reduces your vision in bright light and causes glare or halos around lights at night. You're more likely to develop a subcapsular cataract if you have diabetes, are very nearsighted, have taken corticosteroid drugs or have had an eye injury or eye surgery.

As you age the lenses in your eyes become less flexible, less transparent and thicker. The lens is made mostly of water and protein fibers. The protein fibers are arranged in a precise manner that makes the lens clear and allows light to pass through without interference. With aging, the composition of the lens undergoes changes and the structure of the protein fibers breaks down. Some of the fibers begin to clump together, clouding small areas of the lens. As the cataract continues to develop, the clouding becomes more dense and involves a greater part of the lens.

Scientists don't know why a lens changes with age. One possibility is damage caused by unstable molecules known as free radicals. Smoking and exposure to UV light are two sources of free radicals. General wear and tear on the lens over the years also may cause the changes in protein fibers.

Age-related changes in the lens aren't the only cause of cataracts. Some people are born with cataracts or develop them during childhood. Such cataracts may be the result of the mother having contracted rubella (German measles) during pregnancy. They may also be due to a chemical imbalance or developmental problem. Congenital cataracts, as they're called, don't always affect vision, but if they do they're usually removed soon after detection.

Rubella

Risk Factors

Everyone is at risk of developing cataracts simply because age is the single greatest risk factor. And by age 65 everyone has some degree of lens clouding, although it may not impair vision. Cataracts are more common in women than in men, and they're more common in blacks than in whites.

Other factors that increase your risk of cataracts include:

• Diabetes
  
  
• Family history of cataracts
  
  
• Previous eye injury or inflammation
  
  
• Previous eye surgery
  
  
• Prolonged use of corticosteroids
  
  
• Excessive consumption of alcohol
  
  
• Excessive exposure to sunlight
  
  
• Exposure to high levels of radiation, such as from cancer therapy
  
  
• Smoking

Diabetes Compiling your family medical history Steroid use: Balancing the risks and benefits Alcoholism What Is Nicotine Addiction?

When to Seek Medical Advice

An eye specialist can detect and track the development of cataracts during routine eye exams. Have your eyes examined:

• Every 2 to 4 years between ages 40 and 64
  
  
• Every year or two beginning at age 65
  
  
• Any time you develop new, unexplained eye symptoms

If you find yourself "fighting" with your eyes — blinking more often to clear your vision of what may feel like a thin film over your eyes — or you experience other symptoms of cataracts, see your eye doctor. An eye doctor can diagnose cataracts with the help of a careful eye exam.

Screening and Diagnosis

The only way to know for sure if you have a cataract is to have an eye examination that includes several tests:

• Visual acuity test. Acuity refers to the sharpness of your vision or how clearly you see an object. In this test, your eye doctor checks to see how well you read letters from across the room. Your eyes are tested one at a time, while the other eye is covered. Using the chart with progressively smaller letters from top to bottom (the standard Snellen chart), your eye doctor determines if you have 20/20 vision or less acute vision.
  
  
• Slit-lamp examination. A slit lamp allows your eye doctor to see the structures at the front of your eye under magnification. The microscope is called a slit lamp because it uses an intense line of light — a slit — to provide oblique illumination of the cornea, the iris, the lens and the space between the iris and cornea. The slit allows your doctor to view these structures in cross section and detect any small abnormalities.
  
  
• Retinal examination. In this procedure, your eye doctor puts dilating drops in your eyes to open your pupils wide and provide a bigger window to the back of your eye. Using a slit lamp or ophthalmoscope, he or she can examine your lens for signs of a cataract and, if needed, determine how dense the clouding is. He or she will also check for glaucoma and, if you have blurred vision or discomfort, for other problems involving the retina and the optic nerve. Dilating drops usually keep your pupils open for a few hours before their effect gradually wears off. Until then, you probably will have difficulty focusing on close objects, but your distance vision shouldn't be affected. With your pupils open this wide, you'll probably need sunglasses for your trip home, especially if it's a bright day. It would be safer to let someone else do the driving.

If you have a cataract, you can discuss treatment options with your eye doctor. If — in addition to having a cataract — you have severe glaucoma or another serious eye condition, removing the cataract may not result in improved vision.

What Is Glaucoma?

Treatment

The only effective treatment for a cataract is surgery to remove the clouded lens and replace it with a clear lens implant. Cataracts can't be cured with medications, dietary supplements, exercise or optical devices. In the early stages of a cataract when symptoms are mild, a good understanding of the condition and a willingness to adjust your lifestyle can help. You can try a few simple approaches to deal with symptoms:

• If you have eyeglasses or contact lenses, make sure they're the most accurate prescription possible.
  
  
• Use a magnifying glass to read.
  
  
• Improve the lighting in your home with more or brighter lamps, for example, ones that can accommodate halogen lights or 100- to 150-watt incandescent bulbs. When you go outside during the day, wear sunglasses to reduce glare.
  
  
• Limit your night driving.

These measures may help for a while, but as the cataract progresses, your vision may deteriorate further. When vision loss starts to interfere with your everyday activities, you'll want to consider cataract surgery.

Cataract surgery is the most common surgery performed on Americans age 65 and older. More than 1.5 million cataract operations are performed each year. This surgery is very successful in restoring vision — more than 95 percent of people who have a cataract removed end up with better vision. Many people report not only better vision but also a reduction in the power of their lens prescription and improvements in the overall quality of their life after the operation.

When is the right time to have a cataract removed?

The decision to have cataract surgery is one that you and your eye doctor make together. You'll probably have plenty of time to consider and discuss your options carefully. In most cases waiting until you're ready to have surgery won't harm your eye. You may not need cataract surgery for many years if at all. In younger people or those with diabetes, however, cataracts may develop more quickly.

Base your decision on your degree of vision loss and your ability to function in daily life. In general, surgery is recommended if the results of your visual acuity test are 20/50 or worse, even with eyeglasses, but this figure isn't set in stone. Think about how the cataract affects your daily life. Can you see to do your job and drive safely? Can you read or watch television in comfort? Is it difficult to cook, shop, do yardwork, climb stairs or take medications? How active are you? Does lack of vision affect your level of independence? Are you afraid you'll trip or fall or bump into something?

The answers to these questions are different for each person. An older person who isn't very active may have less need for sharp vision than a younger person who needs to drive a car and earn a living. Some people with only minor vision loss from a cataract might want surgery because of problems with glare or double vision. Sometimes a cataract should be removed even if it doesn't cause major problems with vision, for example, if it's preventing the treatment of another eye problem, such as age-related macular degeneration, diabetic retinopathy or retinal detachment.

If you have cataracts in both eyes and decide to have surgery, your ophthalmologist typically removes the cataract in one eye at a time. This allows time for the first eye to heal before the second eye is operated on.

What Is Macular Degeneration? What Is Diabetic Retinopathy? What Is Retinal Detachment?

What happens during cataract surgery?

Important advances in surgical technique and more sophisticated technology have helped make surgery a safe and effective treatment for cataracts. Two things happen during cataract surgery — the clouded lens is removed, and a clear artificial lens is inserted.

Prior to surgery, your eye doctor measures the size and shape of your eye to determine the proper lens implant power. This measurement is made with a painless ultrasound test. Cataract surgery is typically an outpatient procedure that takes less than an hour. Most people are awake, relaxed and comfortable during the surgery, needing only local anesthesia. On rare occasions some people may need general anesthesia.

Surgical methods used to remove cataracts include:

• Phacoemulsification (fak-o-e-mul-sih-fih-KA-shun). This is the most commonly used procedure to remove a cataract. Your surgeon removes the cataract while leaving most of the outer layer (lens capsule) in place. The capsule helps support the lens implant when it's inserted.
  
  During phacoemulsification, phaco for short, your surgeon makes a small incision, about 1/8 inch, which is about 3 millimeters (mm), where the cornea meets the conjunctiva and inserts a needle-thin probe. The surgeon then uses the probe, which vibrates with ultrasound waves, to break up (emulsify) the cataract and suction out the fragments. The lens capsule is left in place to provide support for the lens implant.
  
  
• Extracapsular cataract extraction. If your cataract has advanced beyond the point where phacoemulsification can effectively break up the clouded lens, your surgeon may do an extracapsular cataract extraction. This procedure requires a larger incision, about 3/8 inch (10 mm), where the cornea and conjunctiva meet. Through this incision your surgeon opens the lens capsule, removes the nucleus in one piece and vacuums out the softer lens cortex, leaving the capsule shell in place.

Once the cataract has been removed through phacoemulsification or the extracapsular method, a clear artificial lens is implanted into the empty lens capsule to replace the original clouded lens. This lens implant, also known as an intraocular lens (IOL), is made of plastic, acrylic or silicone. It requires no care and becomes a permanent part of your eye. Whether or not you wore glasses before surgery, after surgery you'll likely need reading glasses.

Some IOLs are rigid plastic and implanted through an incision that requires several stitches (sutures) to close. However, many IOLs are flexible, allowing a smaller incision that requires no stitches. The surgeon can fold this type of lens and insert it into the empty capsule where the natural lens used to be. Once in place the lens unfolds to about 1/4 inch (6 mm).

After cataract surgery

With phacoemulsification and foldable lens implants, surgical incisions are very small, and no sutures are required. If all goes well you'll heal fast, and your vision will start to improve within a few days. If your surgery required a larger incision and sutures, full healing might take about 4 weeks.

Normally you can go home on the same day as surgery, but you won't be able to drive, so make sure to arrange for a ride home. You'll typically see your eye doctor the next day and during the next 4 to 6 weeks so that he or she can check the healing progress.

It's normal to feel mild discomfort for a couple of days after surgery. Avoid rubbing or pressing on your eye. Clean your eyelids with tissue or cotton balls to remove any crusty discharge. You may wear an eye patch or protective shield the day of surgery. Your doctor may prescribe medications to prevent infection and control eye pressure. After a couple of days, all discomfort should disappear.

Contact your doctor immediately if you experience any of the following signs or symptoms after cataract surgery:

• Vision loss
  
  
• Pain that persists despite the use of over-the-counter pain medications
  
  
• A significant increase in eye redness
  
  
• Light flashes or multiple spots (floaters) in front of your eye
  
  
• Nausea, vomiting or excessive coughing

Most people need to wear glasses after cataract surgery. Astigmatism — a focusing problem that occurs when your cornea isn't curved evenly in all directions — is common but is less of a problem when the surgery involves a small incision. You can usually get a final prescription for eyeglasses 3 to 6 weeks after surgery.

Complications after cataract surgery are relatively rare, and most can be treated. They include inflammation, infection, bleeding, swelling, retinal detachment and glaucoma. The risks are greater for people who have other eye diseases or serious medical problems. Occasionally cataract surgery fails to improve vision because of conditions such as glaucoma or macular degeneration. It is important to evaluate and treat these other eye problems, if possible, before making the decision to proceed with cataract surgery.

The second cataract

You may have heard of a second cataract, or aftercataract. This condition occurs when the back of the lens capsule — the part of the lens that wasn't removed during surgery and that now supports the lens implant — eventually becomes cloudy and blurs your vision. Another term for this condition is posterior capsule opacification (PCO). PCO can develop months or years after cataract surgery. It happens about 15 percent to 20 percent of the time. The gradual clouding is the result of cell growth on the back of the capsule.

Treatment for PCO is simple and quick. It involves a technique called YAG laser capsulotomy, in which a laser beam is used to make a small opening in the clouded capsule to let light pass through. Capsulotomy means "cutting into the capsule," and

YAG is an abbreviation of yttrium-aluminum-garnet, the type of laser used for the procedure.

Laser capsulotomy is a painless outpatient procedure that usually takes less than 5 minutes. After the procedure you typically stay in the doctor's office for about an hour to make sure your eye pressure isn't elevated. In some people, particularly those who have glaucoma or are extremely nearsighted, YAG laser surgery can raise eye pressure. Other complications are rare but can include swelling of the macula and a detached retina.

Prevention

Most cataracts occur with age and can't be avoided altogether. Regular eye exams remain the key to their early detection. You can take steps to help slow or prevent the development of cataracts:

• Don't smoke. Smoking produces free radicals, increasing your risk of cataracts.
  
  
• Eat a balanced diet with plenty of fruits and vegetables.
  
  
• Limit alcohol. Excessive drinking may increase your risk of developing cataracts.
  
  
• Protect yourself from the sun. Ultraviolet light may contribute to the development of cataracts. It's good to wear sunglasses when you are outdoors.
  
  
• Follow your treatment plan if you have diabetes or other medical conditions.

Researchers continue to explore new ways to prevent and treat cataracts. If you do have a cataract, your chances of fully restoring your vision with cataract surgery are excellent if you have no other eye diseases.

Senior Health Center

— August 1, 2002 —