Eye Facts


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 help 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 can block light from the retina. Cataracts are one of the most common causes of impaired vision in the world.

Normal Eye (left) Cataract Eye (right)Normal Eye                              Cataract Eye

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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 and 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 occasionally doubled 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, phacoemulsification, an ultrasonic device is used to fragment and remove the lens.

The surgery is always done in a sterile operating facility, most often using eye drop or local anesthesia. The operation generally lasts 10 to 30 minutes. Under normal circumstances, patients can go home shortly after the surgery and can return to light work the next day.

How is light focused on the retina once the lens is removed?

With the lens gone, the focusing power of the lens needs to be replaced. In the pat this was done with thick glasses or contact lenses. Nowadays an artificial lens is usually placed in the space where the patient’s own lens used to be. This is called an intraocular lens implant (IOL) and is made of plastic or silicone. Most such implants are foldable so that they can be placed into the eye through a very small incision, often in the range of one-tenth of an inch.

How safe is cataract surgery?

Cataract extraction is the most frequently performed surgical procedure in Americans over 65 years of age. Over 2-million cataract operations are performed in the United States every year.
Other problems may occur.

Can both eyes be operated on at once?

If a patient has cataracts in both eyes, the second eye is usually 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 cataract extraction, an “after-cataract” may develop. This occurs when the lens membrane that remains in the eye after surgery becomes cloudy. An after-cataract may cause decreased vision. Lasers are 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 an informational series and should not be used as a substitute for medical advice. For eye appointments, call (312) 996-6591. All Eye Facts illustrations and images are copyright protected and are the property of the UIC Board of Trustees. Unauthorized use of the images is prohibited. For usage of any Eye Facts content or illustrations please contact the Office of Medical Illustration at eyeweb@uic.edu or 312-996-5309 for licensing.
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