My friend has been wearing contacts for 20 years, and about five weeks ago her vision became blurry. She went in for her regular check-up and found her eyesight had gone from 20/20 with correction to 20/140. She was told not to wear her contacts and to only wear glasses because there were some abrasions and edema of the cornea. The doctor told her the problem was possibly caused by a deficient immune system or abuse of steroids. Neither situation seems to fit her. What else could it be?

T.

The three most frequent medical problems with contact lenses include corneal infection, giant papillary conjunctivitis (inflammation of the inside of the upper lid) and corneal hypoxia (lack of oxygen to the cornea). Both infection and hypoxia can cause swelling (edema) of the cornea, along with blurring or loss of vision.

As your friend's doctor mentioned, a deficient immune system or abuse of steroid eyedrops can predispose a patient to corneal infections. However, people with normal immune systems can also get corneal infections. In my experience, the greatest risk factor for infections associated with contact lenses is failure to remove contacts before going to sleep. Studies have demonstrated that the risk of corneal infection can be increased by more than 20-fold when a person sleeps in contact lenses. Therefore, unless the contacts are specifically designed for overnight wear, I recommend that people never sleep in contact lenses.

Patients who develop corneal infections are usually treated with antibiotic eyedrops and told to stop wearing their contacts. Since uncontrolled infections pose a risk of blindness, it may be necessary to see an eye doctor on a daily basis until the infection is contained. I would not recommend any general medical tests for an otherwise healthy person who develops a corneal infection while wearing contacts.