Reviewed by Christopher T. Hood, M.D.
On this page:
- What Is a Cataract?
- What Is a Cataract? - Video
- Risk Factors
- Tests and Diagnosis
- Treatment and Drugs
- Clinic Information
A cataract is a clouding of the lens of your eye. As you age, proteins in your lens begin to break down and the lens becomes cloudy. You may not even realize you have a cataract because it usually grows very slowly and may not impede vision early on. While cataracts are rarely dangerous, after a number of years they will likely affect vision. By age 65, over 90 percent of people have a cataract and half of the people between the ages of 75 and 85 have lost some vision due to a cataract. A cataract is not caused by overuse of your eyes and it does not travel from one eye to the other.
- A decrease in the clarity of vision that is not correctable with glasses
- Colors that appear faded or washed out
- Sensitivity to light, glare, and halos around lights
- Frequent changes to eyeglass prescriptions
An ophthalmologist or optometrist will be able to diagnose a cataract during a dilated eye examination.
The human lens is transparent so that light can travel through it easily. It has no blood supply and is 65 percent water. Although new cells are being made for the lens continuously throughout our lifetime, many factors combine as we age to cause areas in the lens to become cloudy, hard, and dense. The lens can then no longer transmit a clear picture to the retina where it can be processed and sent through the optic nerve to the brain. Cataracts can have many causes, as described below.
This is the most common kind of cataract. There are three subclassifications, based on location: nuclear, cortical, and posterior subcapsular.
Although it is not common, some babies are born with cataracts or develop them within the first year of life.
This type of cataract results from an injury to the eye.
This is a cataract that is caused either by medications (most commonly prednisone or other corticosteroids) or disease, like diabetes. Cataracts are 10 times more common in diabetic patients than in the general population.
Risk factors associated with cataracts include:
- Heavy drinking
- High blood pressure
- Previous eye injuries
- Family history
- Too much UV light (sun) exposure
- Exposure to radiation from x-rays and cancer treatments
Cataracts can be diagnosed by your eye care professional during a dilated eye exam. You may also have your vision checked in different lighting conditions and with an updated glasses prescription. Imaging or invasive testing is not required to diagnose a cataract. A complete eye exam is necessary to determine if anything else is contributing to your visual symptoms.
Although there is no way to prevent cataracts from forming, there is some evidence that protecting your eyes from ultraviolet light may prevent or slow the progression of cataracts. Smoking also increases the rate of cataract formation, so stopping smoking will decrease the risk. Once cataracts have formed, the only treatment is surgical removal of the cataract and replacement with an artificial lens. There are different types and powers of lenses that your surgeon can implant during surgery, including lenses that help correct astigmatism. After surgery, your need for glasses will often be reduced, but not eliminated. You and your surgeon will discuss which implant lens type and power is the right choice for you. Medications cannot be used to treat a cataract. Surgery is typically performed on an outpatient basis under local anesthesia. When the cataract has become severe enough that it compromises your quality of life, you and your ophthalmologist will discuss the appropriate time to remove it.
For more information, see the Comprehensive Ophthalmology and Cataract Sugery Clinic and the complete Clinic Services listing of the U-M Kellogg Eye Center.