Contact Lenses
Clear or slightly colored plastic lenses worn directly on the eyeball to correct vision problems, held in place over the cornea by a thin layer of tears.
The concept of corrective lenses that sit directly on the eyeball was developed in the ninth century, but it was not until the late 20th century that manufacturing and grinding techniques for contact lenses were perfected. Originally contact lenses were made of glass, then later of hard plastic, and still later of flexible, highly oxygen-permeable soft plastic. Today, the majority of lenses worn are of two basic types: rigid gas permeable (so-called "hard" lenses) and soft lenses. Hard lenses are smaller and more durable, but require a longer period of adjustment for the wearer. Hard contact lenses can correct some vision problems, like astigmatism, that the soft lenses cannot. The soft lenses are slightly larger than hard lenses. They are more comfortable and lessexpensive, but can be easily torn. The latest generations of contact lenses are extended wear and disposable soft lenses. Extended wear lenses are intended to be worn for several weeks at a time, while disposable lenses are thrown away every day or every few weeks, or in the newest versions, every day. The Contact Lens Council reports that 26 million Americans wear contact lenses. Among contact lens wearers, approximately 80% wear the soft type and 18% wear rigid gas-permeable lenses. The Council reports that about 11 % of contact lens wearers, approximately 2.8 million people, are under 18.
Infants
There are few instances when corrective lenses—eyeglasses or contacts—are prescribed for infants. However, when an infant develops cataracts, a condition known as infantile aphakia, contact lenses may be prescribed following surgery. In 1993, the Journal of the American Medical Association reported that contact lenses were safe and effective for use with infants following cataract surgery. Routine care of the lenses was easily learned by the baby's parents or caregivers.
Preschool and School-Age Children
Contact lenses are a significant improvement over eyeglasses for children and adolescents who participate in sports or outdoor activities.
Contact lenses are recommended for most athletes who need corrective eyewear. Often, a single pair of lenses is less expensive than the combined cost of glasses and prescription goggles. Swimmers especially can benefit from being able to see underwater while wearing regular goggles over their contact lenses. Because contact lenses tend to dry the eye, swimmers and all athletes should take care to blink several times before and after an activity session in order to assure natural cleansing. If any pool water enters a swimmer's eyes, the lenses should be thoroughly disinfected as soon as possible to remove pool contaminants. Children who like spending time looking into a telescope, microscope, or binoculars may also prefer contacts over eyeglasses.
The primary drawback to wearing contact lenses, especially for children, is the requirement that they be cleaned and disinfected daily in order to prevent an infection, which could result in permanent damage to the eye. Careful choice of lenses and consistent lens care will minimize the risk of infection. Wearers of hard lenses are the least prone to infection but the lenses are much less comfortable, more expensive, and can pop out of the eye more easily than soft lenses. Daily wear soft lenses put the wearer at a slightly higher risk of infection because they absorb more external liquids and airborne contaminants. Extended wear soft lenses in particular pose a much greater risk than daily wear soft lenses. Though extended-wear lenses are extremely thin and allow some oxygen—necessary for healthy eyes—to reach the cornea, they are worn continuously, including at night while the eyelid is closed. Bacteria can easily grow more easily under these conditions. Twenty-one in 1,000 extended lens wearers develop infections as opposed to 4 in 1,000 daily soft lens wearers. To reduce this risk, eye care professionals now recommend removing extended wear lenses at night. In addition, newer versions of extended wear lenses being developed may offer increased oxygen exchange and pose less risk. Disposable lenses may also help to prevent infection, since the wearer is guaranteed a clean pair of lenses every few weeks or every day.
For Further Study
Organizations
Contact Lens Council
Address: 8201 Corporate Drive, Suite 850
Landover, MD 20785
Telephone: (800) 884-4252
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