Cataracts

Reviewed:
Last Updated: 3/01/90
Created: 3/01/90
Revised:

Think of how hard it is to see through a frosty window in winter. Similarly, the lens of the eye can become fogged, or opaque, resulting in decreased vision. The lens lies behind the iris and is about the size and shape of an aspirin tablet. Its function is to focus light on the retina (at the back of the eye).

A cataract is the name given to the clouding of the normally clear lens. This clouding blocks light from the retina. Cataracts are one of the most common causes of impaired vision in the world.

Normal Eye	Cataract Eye

What causes a cataract?
Clouding of the lens is a natural aging process, which usually begins in the third or fourth decade of life. The age at which a cataract may begin to affect a person's vision varies. This depends on the density of the clouding and the extent of the area of the lens involved.

In addition to aging, other well-recognized causes of cataracts are:

• An injury to the eye.

• Long-term use of certain medicines, such as Corticosteroids.

• Medical conditions such as diabetes.

In uncommon cases, cataracts may be inherited. Additionally, there is some evidence that years of exposure to the ultraviolet rays of the sun may play a role in cataract development.

How do I know if I have a cataract?
Cataracts usually develop gradually over a number of years. In most cases, they form in both eyes, though not usually at the same rate. A person may or may not be aware that a cataract is developing. The main symptom of cataract formation is painless loss of vision. The visual effects— if any—depend on the size, location and density of the cataract.

Common symptoms include:

• Progressively worsening vision.

• Blurred or double vision.

• Sensitivity to light and glare.

An ophthalmologist can see the earliest evidence of a cataract using sophisticated instruments to view the inside of the eye. Most cataracts are not visible to the naked eye until they are very mature, or dense (sometimes called "ripe"). In this advanced state, the pupil may appear white or yellowish.

What should be done about a cataract?
Once a cataract has caused visual loss, surgery is the only accepted treatment. Opinions vary on when to perform cataract surgery. The decision to operate is based on each patient's individual needs. If a cataract is causing loss of sight that interferes with a person's normal activities, it is appropriate to consider cataract surgery. A cataract must no longer be "ripe" before it can be removed.

What is cataract surgery?
Basically, cataract surgery involves removing the cloudy lens. In the most commonly performed technique, extracapsular cataract extraction, a portion of the lens membrane (capsule) is left intact. Another method, phacoemulsification, uses an ultrasonic device to fragment and remove the lens.

The surgery is always done in a sterile operating facility, most often using local anesthesia. The operation generally lasts under one hour. Under normal circumstances, patients can go home several hours after the surgery and can return to light work the next day.

Are lasers used?
Contrary to popular belief, lasers cannot remove cataracts. They are used, however, to open an "after-cataract".

Will I need to wear "cataract glasses"?
Once the lens is removed, the patient will not be able to focus incoming light rays and see clearly. Thus, an artificial replacement is necessary to restore sight. Until recently, spectacles and contact lenses were the most often used devices to focus light rays. However, the thick "cataract glasses" do not provide good side vision, and contact lenses sometimes cause complications such as infections.

These complexities led to the development of a much better "substitute lens": the intraocular lens. This device is a small, permanent, plastic lens inserted into the eye immediately after removal of the patient's cataractous lens. Today the intraocular lens is by far the most popular choice of visual correction following cataract removal. It is used in over 90 percent of cataract surgeries.

On the other hand, these lens implants are not suitable for every patient. In rare cases, they may not be safe because the patient has had previous eye disease or trauma. For these patients, glasses or hard or soft contact lenses are recommended.

How safe is cataract surgery?
Cataract extraction is the most frequently performed surgical procedure in Americans over 65 years of age. Nearly 1.4 million cataract operations are performed in the United States every year.

Due to advances in surgical training and equipment, cataract extraction has become one of the safest of all surgeries. More than 90 percent of cataract operations are successful in restoring useful vision. However, as with any surgery, complications can occur. For example, glaucoma, bleeding or infection in the eye may develop after surgery, or the retina may become detached.

Can both eyes be operated on at once?
If a patient has cataracts in both eyes, the second eye is operated on at a different time. This is done so that in the rare event of a serious surgical complication (such as an infection) only one eye will be affected.

What is an "after-cataract"?
Months or years after extracapsular cataract extraction, an "after-cataract" often develops. This occurs when the lens membrane that remains in the eye during surgery becomes cloudy. An after-cataract may cause decreased vision. Fortunately, lasers can be used to open the membrane and restore vision.

Can cataracts be prevented?
No proven prevention of cataracts exists. However, as cataracts develop slowly enough to be watched and surgery is very effective, permanent loss of vision can be prevented in most cases. Therefore, if you think you have a cataract, you should consult an ophthalmologist.

"Eye Facts" is intended as an informational series and should not be used as a substitute for medical advice.

The Comprehensive Ophthalmology Service is located in the Eye and Ear Infirmary at 1855 W. Taylor Street, Chicago IL 60612. For eye appointments, call (312) 996-4356.

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