WELLNESS

Caring for contact lenses

More than 140 million Americans require some form of vision correction. Of this number, 24 million wear contact lenses. The U.S. contact lens market is shared by daily and extended wear types of soft and rigid lenses. Lens disposability, advanced bifocal designs and effective astigmatism correction have produced an increased interest in contact lens wear. Reports of microbial keratitis have produced an increased interest of proper lens care and risks associated with lens wear. The incidence of ulcerative keratitis varies from 41 per 100,000 for daily wear soft contact lenses to 209 per 100,000 wearing population for extended wear contact lenses. When compared with other life risks, one is more likely to have been the victim of a robbery or to suffer an IRS audit than to have a contact lens-related corneal infection.

History

Shortly after the introduction of the corneal hard contact lens, it become apparent that proteins, mucus and oils from the tears would coat the lens surfaces. Initial hard contact lens care was expedient; they were stored dry. In the early 1970s when soft contact lenses were introduced, lens care became more sophisticated, time-consuming and expensive. Early soft lens care utilized consumer-prepared saline (salt tablets dissolved in distilled water) to be used in conjunction with thermal disinfection. Although the considerable risks of using homemade saline have been well illuminated, the U.S. Food and Drug Administration (FDA) continues to allow their presence in the U.S. market. Bacterial corneal ulcers, predominantly Psuedomona sp, have been associated with the use of homemade saline. In addition, as reported in a study by the U.S. Centers for Disease Control and Prevention, 50 percent of acanthamoebic keratitis cases were among contact lens wearers who used home-prepared saline.

Current recommendations

Hard and rigid gas permeable contact lens care requires the following daily care regimen:

*Surfactant cleaning and sterile saline rinse followed by overnight storage in a chemical disinfectant/conditioning solution.

*Lens storage cases should be rinsed and left open to air dry during the day and disinfected (scalded) in boiling water weekly.

Soft lens care is slightly more time consuming although the basic steps are similar. Following surfactant cleaning and sterile saline rinse, the lens must be disinfected by one of the following methods:

*Cold chemical

*Oxidation (hydrogen peroxide)

*Thermal disinfection

Regardless of the method of prescribed disinfection, the daily surfactant cleaning of all lenses remians a very important step. It is the cleaning step that debulks the lens, removing the organic load and preparing the lens surfaces for disinfection. If weekly enzymatic treated is used, the lens needs to be surfactantly cleaned prior to enzymatic treament and following enzymatic treatment to remove residual enzyme left on the lens surfaces. The lenses should then be disinfected prior to being worn the following day.

Michael A. Ward is the director of the Contact Lens Service of the Emory Eye Center. The publication of "Wellness" is coordinated through the Seretean Center for Health Promotion.