Contact lenses are thin, clear disks of plastic that float on the surface of the eye. They correct vision like eyeglasses do and are safe when used with care.
Contact lenses are used to correct the same conditions that eyeglasses do:
myopia (nearsightedness), hyperopia (farsightedness), astigmatism (blurred vision
due to the shape of the cornea) and presbyopia (inability to see close up).
Millions of people around the world wear contact lenses. Depending on your lifestyle,
your motivation and the health of your eyes, contact lenses may provide a safe and
effective alternative to eyeglasses when used with proper care and maintenance.
There are two general types of contact lenses: hard and soft. The hard lenses most
commonly used today are rigid, gas-permeable lenses (RGP for short). They are made
of plastics and other materials such as silicone or fluoropolymers. Hard lenses hold
their shape, yet allow the free flow of oxygen through the lenses to the cornea. RGP
lenses may be the best choice when the cornea has enough astigmatism (is shaped
like an egg instead of an orange) that a soft lens will not provide sharp vision. They
may also be preferable when a person has allergies or tends to form protein deposits
on his or her contacts.
Soft lenses are the choice of most contact lens wearers. These lenses are comfortable and come in many versions, depending on how you want to wear them.
Daily-wear lenses are the least expensive, are removed nightly and are replaced on an individualized schedule. They should not be used as an extended-wear lens.
Extended-wear lenses are worn overnight but are removed at least weekly for thorough cleaning and disinfection. They are being recommended less frequently since there is a greater risk of corneal infection with any overnight wear of contact lenses.
Disposable-wear lenses are more expensive, but convenient. They are removed nightly and replaced on a daily, weekly or monthly basis. Disposable lenses are sometimes recommended for people with allergies and for those who tend to form deposits on their lenses.
Cosmetic or decorative contact lenses are colored contacts that change the appearance of your eye color, and in the case of circle lenses also make your iris appear bigger. Decorative lenses are available by prescription and should only be worn after an eye exam and fitting by qualified eye care professional. Over-the-counter decorative contacts, including circle lenses, are illegal and pose a serious danger to your eye heath. They can cause eye injury, eye infection, and vision loss.
Toric soft contact lenses can correct astigmatism, but sometimes not as well as RGP lenses do. They usually cost more than other contact lenses.
Bifocal or multifocal contact lenses are available in both soft and RPG varieties. They can correct nearsightedness, farsightedness and astigmatism in combination with presbyopia. Cleaning and disinfection are specific to the lens material. Visual quality is often not as good as with single vision lenses; however, for some people the ability to correct presbyopia is worth it.
Source: American Academy of Ophthalmology, www.geteyesmart.com