Cataracts

Definition
A cataract is a cloudiness or opacity in the normally transparent crystalline lens of the eye. This cloudiness can cause a decrease in vision and may lead to eventual blindness.

Description
The human eye has several parts. The outer layer of the eyeball consists of a transparent dome-shaped cornea and an opaque, white sclera. The cornea and sclera help protect the eye. The next layer includes the iris, pupil, and ciliary body. The iris is the colored part of the eye and the pupil is the small dark round hole in the middle of the iris. The pupil and iris allow light into the eye. The ciliary body contains muscles that help in the eye’s focusing ability. The lens lies behind the pupil and iris. It is covered by a cellophane-like capsule. The lens is normally transparent, elliptical in shape, and somewhat elastic. This elasticity allows the lens to focus on both near and far objects. The lens isattached to the ciliary body by fibers (zonules of Zinn).
Muscles in the ciliary body act on the zonules, which then change the shape of the lens. This process is called accommodation—the lens focuses images to help make vision clear. As people age, the lens hardens and changes shape less easily. As a result, the accommodation process becomes more difficult, making it harder to see things up close. This generally occurs around the age of 40 and continues until about age 65.
The condition is called presbyopia. It is a normal condition of aging, generally resulting in the need for reading glasses.

The lens is made up of approximately 35% protein and 65% water. As people age, degenerative changes in the lens’s proteins occur. Changes in the proteins, water content, enzymes, and other chemicals are some of the reasons for the formation of a cataract.

The major areas of the lens are the nucleus, the cortex, and the capsule. The nucleus is in the center of the lens, the cortex surrounds the nucleus, and the capsule is the outer layer. Opacities can occur in any area of the lens. Cataracts, then, can be classified according to location (nuclear, cortical, or posterior subcapular cataracts). The density and location of the cataract determine the amount of vision affected. If the cataract forms in the area of the lens directly behind the pupil, vision may be significantly impaired. A cataract that occurs on the outer edges or side of the lens will create less of a visual problem.

Cataracts in the elderly are so common that they are thought to be a normal part of the aging process. Between the ages of 52 and 64, there is a 50% chance of having a cataract, while at least 70% of those 70 and older are affected. In 2004, it was revealed that blacks are twice as likely to develop cataracts as whites.
Cataracts associated with aging (senile or age-related cataracts) most often occur in both eyes, with each cataract progressing at a different rate. Initially, cataracts may not affect vision. If the cataract remains small or at the periphery of the lens, the visual changes may be minor.

Cataracts that occur in people other than the elderly are much less common. Congenital cataracts occur very rarely in newborns. Genetic defects or an infection or disease in the mother during pregnancy are among the causes of congenital cataracts. Traumatic cataracts may develop after a foreign body or trauma injures the lens or eye. Systemic illnesses, such as diabetes, may result in cataracts. Cataracts can also occur secondary to other eye diseases—for example, an inflammation of the inner layer of the eye (uveitis) or glaucoma. Such cataracts are called complicated cataracts. Toxic cataracts result from chemical toxicity, such as steroid use. Cataracts can also result from exposure to the sun’s ultraviolet (UV) rays.

Types of Cataracts
    * Nuclear Sclerotic Cataract – This is the most common type of cataract that occurs with aging. The natural lens becomes more dense and brownish in coloration.
    * Posterior Sub Capsular Cataract (PSC) – This type of cataract may occur earlier in life than nuclear sclerosis. It is a plaque on the back surface of the lens. Patients with diabetes, radiation treatment, and trauma are more prone to develop this type of cataract.
    * Cortical Cataract – Gray or white clefts develop in the lens.
    * Combined Form – Many cataracts are a combination of the types of cataracts listed above.

Cataract Treatments

Mild Cataracts
With mild cataracts, there is often a shift in your glasses prescription. Most patients become more nearsighted (myopic). This change may cause difficulty with distance vision as well as visual side effects such as glare with night driving. Often, a minor change in your glasses or contact lens prescription will improve your vision sufficiently so that you can perform your daily activities. It is important to realize that as the cataract progresses, your glasses prescription may need to be updated. At Eye Doctors of Washington, we recommend that mild cataracts be observed every six to 12 months.

Vitamins
There are no medical remedies to reduce or eliminate cataracts. Recent clinical studies have shown that the use of Vitamin C may slow the progression of cataracts. We recommend the use of at least 100 units of Vitamin C. This amount is present in most daily multi-vitamin supplements. It is important to realize that excessive amounts of vitamins can be hazardous to your health. At the recommended dosage, Vitamin C is quite safe for most individuals. If you have any questions or concerns about the use of vitamins, you should contact your family physician or internist prior to initiating cataract treatment.

Visually Significant Cataracts
At some point, changes in the glasses prescription will not be sufficient to improve your vision. The only effective cataract treatment is to remove the cloudy lens. Fortunately, modern cataract surgery is safe and effective with excellent results and minimal discomfort.

Cataract Symptoms and Signs
A cataract starts out small and at first has little effect on your vision. You may notice that your vision is blurred a little, like looking through a cloudy piece of glass or viewing an impressionist painting.
A cataract may make light from the sun or a lamp seem too bright or glaring. Or you may notice when you drive at night that the oncoming headlights cause more glare than before. Colors may not appear as bright as they once did.

The type of cataract you have will affect exactly which symptoms you experience and how soon they will occur. When a nuclear cataract first develops, it can bring about a temporary improvement in your near vision, called "second sight." Unfortunately, the improved vision is short-lived and will disappear as the cataract worsens. On the other hand, a subcapsular cataract may not produce any symptoms until it's well-developed. If you think you have a cataract, see an eye doctor for an exam to find out for sure.

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 close-up 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. When are you most likely to have a cataract?

The term "age-related" 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 age-related 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 age-related 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 age-related macular degeneration, glaucoma, and other vision disorders. Early treatment for many eye diseases may save your sight.

What Causes Cataracts?
No one knows for sure why the eye's lens changes as we age, forming cataracts. Researchers are gradually identifying factors that may cause cataracts — and information that may help to prevent them.

Many studies suggest that exposure to ultraviolet light is associated with cataract development, so eye care practitioners recommend wearing sunglasses and a wide-brimmed hat to reduce your exposure. Other types of radiation may also be causes. For example, a 2005 study conducted in Iceland suggests that airline pilots have a higher risk of developing nuclear cataract than non-pilots and that the cause may be exposure to cosmic radiation. A similar theory suggests that astronauts, too, are at risk from cosmic radiation.

Other studies suggest people with diabetes are at risk for developing a cataract. The same goes for users of steroids, diuretics and major tranquilizers, but more studies are needed to distinguish the effect of the disease from the consequences of the drugs themselves. Some eye care practitioners believe that a diet high in antioxidants, such as beta-carotene (vitamin A), selenium and vitamins C and E, may forestall cataract development. Meanwhile, eating a lot of salt may increase your risk.

Other risk factors include cigarette smoke, air pollution and heavy alcohol consumption. A small study published in 2002 found lead exposure to be a risk factor; another study in December 2004, of 795 men age 60 and older, came to a similar conclusion. But larger studies are needed to confirm whether lead can definitely put you at risk and, if so, whether the risk is from a one-time dose at a particular time in life or from chronic exposure over years.*

Cataract Treatment
When symptoms begin to appear, you may be able to improve your vision for a while using new glasses, strong bifocals, magnification, appropriate lighting or other visual aids.
Think about surgery when your cataracts have progressed enough to seriously impair your vision and affect your daily life. Many people consider poor vision an inevitable fact of aging, but cataract surgery is a simple, relatively painless procedure to regain vision.

Cataract surgery is very successful in restoring vision. In fact, it is the most frequently performed surgery in the United States, with more than 3 million Americans undergoing cataract surgery each year. Nine out of 10 people who have cataract surgery regain very good vision, somewhere between 20/20 and 20/40.

During surgery, the surgeon will remove your clouded lens and in most cases replace it with a clear, plastic intraocular lens (IOL).
New IOLs are being developed all the time to make the surgery less complicated for surgeons and the lenses more helpful to patients. Presbyopia-correcting IOLs potentially help you see at all distances, not just one. Another new type of IOL blocks both ultraviolet and blue light rays, which research indicates may damage the retina (see illustration).

Read more on this website about what to expect if you have cataract surgery and how to deal with rare cataract surgery complications. Also, men should be aware that certain prostate drugs can cause intraoperative floppy iris syndrome (IFIS) during a cataract procedure.

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 age-related 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.

Resources
GAL E ENCYCLOP E D I A OF MED I C INE
http://www.nei.nih.gov/health
http://www.allaboutvision.com

http://www.edow.com