Soft lens users: clean 'em or weep.

Soft lens users: Clean 'em or weep

For some years, optometrists and ophthalmologists have noted an increase in the number of corneal infections associated with the use of soft contact lenses, but the precise cause of the problem has been difficult to determine. Now, researchers at the Centers for Disease Control (CDC) in Atlanta have released the results of a study that sought to identify risk factors linking soft lens wear with a rare amoebic infection of the cornea, Acanthamoeba keratitis. They conclude that Acanthamoeba infection rates appear to be closely related to improper maintenance and cleaning of soft lenses by users.

In particular, they report, improper use of homemade saline solutions may be a major cause of the amoebic infections, which have been reported to the CDC with increasing frequency among soft lens users since 1985. The amoeba can be found in water, soil and saline, where it feeds on yeast cells and bacteria. Ocular infection with Acanthamoeba can result in partial or total loss of vision.

Jeanette K. Stehr-Green and her colleagues report in the July 3 JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION that Acanthamoeba patients "were significantly more likely than controls to use homemade saline instead of commercially prepared saline and...to disinfect their lenses less frequently than recommended by lens manufacturers." Homemade saline solutions--made by dissolving salt tablets in water--are not sterile, they point out, even when made with distilled water, and can quickly become overgrown with potentially infectious bacteria and amoebas. These nonsterile salines are meant to be used only if the contact lenses are to be subsequently sterilized.

Richard Lippman, director of the Food and Drug Administration's Division of Ophthalmic Devices, told SCIENCE NEWS, "We're very concerned about the use of salt-tablet solution because people use it incorrectly as a rinse nd eyedrops." The FDA is currently talking to salt-tablet manufacturers about making warning labes "more readable," Lippman says. He notes that Acanthamoeba keratitis is still not common (only about 100 cases have been reported in the United States since 1973) in comparison to the bacterial infections and corneal ulcers that have for some time been associated with the use of soft contact lenses. Nevertheless, he says, "I have to factor in the seriousness of Acanthamoeba. Corneal ulcers can usually be caught and treated, but we throw everything in the book at these amoebas, and patients may still end up needing corneal transplants."