Contact Lenses... What You Need to Know
Contact lenses, like eyeglasses or refractive surgery, can correct your nearsightedness, farsightedness, and astigmatism. Of the people who need vision correction in the United States, about one in five wear contact lenses.
While some people enjoy the fashion statement of eyeglasses, others prefer their appearance without them. Contact lenses can achieve this without irreversible surgery. Contact lenses can also provide a full field of unobstructed vision, which is good for participation in sports.
If you're new to contact lenses, your first step is to see an eye doctor. In the United States, contact lenses are a prescription item, just like pharmaceuticals. They must be prescribed and properly fitted by an eye care professional. Your eye care professional will evaluate your visual needs, your eye structure, and your tears to help determine the best type of lens for you.
Contact Lens Materials
- Hard Lenses are made from PMMA - also known as Plexiglas or Lucite. These lenses are virtually obsolete and rarely used.
- Soft Lenses are made from gel-like, water-containing plastics, and are most common. They're a bit larger in size than your iris (the colored part of your eye.)
- GP Lenses, also known as RGP or "oxygen permeable" lenses, are made from rigid, waterless plastics and are especially good for presbyopia and high astigmatism. These lenses are usually about eight millimeters in diameter, which is smaller than your iris.
Contact Lens Designs
- Spherical Contact Lenses are the typical, rounded design of contact lenses, which can correct myopia (nearsightedness) or hyperopia (farsightedness.)
- Bifocal Contact Lenses contain different zones for near and far vision to correct presbyopia, which is the age-related, decreased ability to obtain a full range of vision.
- Toric Contact Lenses correct for astigmatism, as well as for myopia and hyperopia.
Disposing of Contact Lenses
One problem with soft contact lenses is that proteins and lipids - which are naturally found in tears - adhere to the surface of the lens, sometimes causing discomfort and providing hiding places for infection (causing germs). Lens-cleaning products help. But over time buildup still occurs, requiring lens replacement.
- Daily disposable - replaced every day
- Disposable (used for daytime wear) - replaced every two weeks
- Disposable (used for overnight wear) - replaced every week
- Continuous wear (used for 30-day wear) - replaced monthly
- Planned replacement - replaced monthly or less frequently