Magazine article Nutrition Health Review

Contact Lenses: New Comfort, New Risks

Magazine article Nutrition Health Review

Contact Lenses: New Comfort, New Risks

Article excerpt

Contact Lenses: New Comfort, New Risks

Advances in contact lens design have made them more than just an increasingly popular way to correct vision. Contact lenses serve as bandages for injured eyes and they even dispense medication. With "hydrophilic" soft lenses, the overwhelming majority of the sixteen million wearers have comfort to go with their corrected vision.

But along with the cosmetic and other advantages of contact lenses go certain risks -- risks of injury to the eye from overwearing, incorrect fit, and improper care of the lenses. That risk is perhaps greatest with the newly developed extended-wear soft lenses, which some manufacturers claim can be worn for up to several months at a time.

According to a New York ophthalmologist, widespread misunderstanding about soft lenses has led many people to believe that contacts are harmless when, in fact, they can cause a great deal of damage if proper precautions are not taken.

Dr. G. Peter Halberg, professor of clinical ophthalmology at New York Medical College and chief of the Contact Lens Service at Saint Vincent's Medical Center, said in an interview that many people, including some physicians, mistakenly believe that soft contact lens material is intrinsically soft. "It is really no softer than cotton fiber," he said. Like cotton, which feels soft when its fibers are in the form of a cotton ball, a hydrophilic lens is made of a hard polymer, which feels soft when it is wet. Should the lens get chipped, it can cut the conjunctiva or cornea just like any other sharp object, he said.

The relatively new soft hydrophilic -- water-containing -- lens affords patients the advantage of instantaneous comfort, unlike its predecessor, the hard lens. The wearability of various types of contact lenses depends on the amount of oxygen that can be transmitted through the lens. Since the cornea -- the clear outer layer of the eye -- doesn't contain blood vessels, it must obtain a certain amount of oxygen directly from the air. Lenses are designed to ensure that the maximum amount of oxygen is delivered -- the more oxygen that reaches the cornea, the more comfortable and longer-wearing the lens will be.

Early contact lenses were made of hard poly(methyl)methacrylate (PMMA) plastic and were difficult, if not impossible, for most people to wear. Oxygen transmission is relatively poor through this material. Within the last decade, however, researchers have utilized the properties of silicone, which has a molecular structure that allows oxygen to pass through it, to create a more oxygen-permeable lens. …

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