Today you can buy contacts from mail-order catalogs, over the phone and on the Internet. You still need a current prescription, though. The Food and Drug Administration (FDA) advises that you order from a reputable supplier and get a regular check-up from your eye doctor to ensure that your lenses fit properly. Ill-fitting lenses can move around in the eye and scratch the cornea.
Although contact lenses are generally safe, they can cause problems. Usually, the problems are minor, such as eye discomfort, redness, or excess tearing. In rare cases, contact lenses, especially extended-wear lenses, can cause a serious infection called a corneal ulcer. This infection can cause redness, pain, tearing and light sensitivity. If left untreated, it can lead to permanent vision damage.
Infections are most common in extended-wear contacts, because the eyes produce fewer oxygen-carrying tears when they are closed during sleep. But even lenses worn just during the day can cause vision loss if they don't allow enough oxygen flow to the cornea. Failing to keep the lenses clean can lead to an infection, for example with the parasitic Acanthamoeba keratitis. This infection causes symptoms similar to those of corneal ulcers.
You should also be careful if you buy cosmetic lenses at places (such as a flea market or costume store) that don't specialize in contact lenses. Lenses that aren't properly sterilized, or that don't fit your cornea correctly, can cause infections and damage your vision.
Next, we'll learn about the history of the contact lens.