About Eye Contacts

Overview

Contact lenses are round plastic disks meant to fit over the eyes to correct faulty vision. According to doctors at the University of Michigan Kellogg Eye Center, the plastic orbs are able to cling to the tears on the cornea with surface tension, much like a drop of water sticking to the side of a glass. Eye contacts are a popular alternative to eyeglasses, and are worn by more than 24 million people in the United States.

Hard Lenses

The first eye contacts came out in the 1960s and were made of polymethyl methacrylate, or PMMA, a plastic that is very durable, but does not allow oxygen to reach the cornea. The lenses move around with each blink of the eye, allowing air to get in under the lens and reach the eye's surface. Though rigid hard lenses are not used as much anymore, they are still available for those who prefer their durability and low cost.

Gas-permeable Lenses

More commonly prescribed types of hard contact lenses are made out of plastics combined with other ingredients such as flouropolymers and silicone that allow oxygen to flow freely to the cornea. Also referred to as RPGs, the lenses work well for those with stigmas and those who prefer more durable heavier lenses.

Soft Lenses

Soft contact lenses are water-based plastic discs that are soft and flexible and allow for a free flow of oxygen to the corneas. Soft contacts are the most popular types of lenses, worn by more than 75 percent of the contact-wearing population, report doctors at the Kellogg Eye Center. Soft contacts come in a variety of styles,Including extended-wear lenses that can be worn for 2 to 4 weeks and be discarded. Extended-wear lenses should be removed each night to let the eye breathe more fully. Daily wear lenses are the most expensive and are discarded each day. They carry the lowest risk for eye infections, however.

Risks

Though contact lenses have improved over the years, minimizing health risks to the eyes, there still are precautions that need to be taken by contact lens wearers. PMMA lenses can scratch the cornea if worn while sleeping. The hard lenses also have a tendency to slide up under the eyelid, making them difficult to remove. Newer lens designs have minimized the movement of both hard and soft contact lenses. Gas-permeable and soft contacts can develop protein build-up over time, making them uncomfortable and causing blurred vision. Lens-related allergies can develop if lenses are not cleaned and replaced according to a doctor's instructions.

Care

Eye contacts must be carefully cared for to prevent bacterial infection and permanent vision damage. They must be cleaned and disinfected regularly and changed on a schedule ordered by the doctor. Sterile solutions used to clean contacts should not be mixed and contacts should never be put in the mouth to moisten. Users should wash their hands thoroughly before removing or inserting contacts and not share lenses with others. Lenses should stay in all day and not be taken out repeatedly throughout the day.