Contact Lens BasicsOver 24 million people choose contact lenses to correct vision. When used with care and proper supervision, contacts are a safe and effective alternative to eyeglasses. And with today's new lens technology, many people who wear eyeglasses can also successfully wear contacts.
Contacts are thin, clear discs that float on the tear film that coats the cornea, the curved front surface of the eye. Contacts correct the same refractive conditions eyeglasses correct: myopia (nearsightedness), hyperopia (farsightedness) and astigmatism (an oval - rather than round - shaped cornea).
Contact lenses can be made from a number of different plastics. The main distinction among them is whether they are hard or soft. Most contact lens wearers in the United States wear soft lenses. Toric soft lenses provide a soft lens alternative for people with slight to moderate astigmatism.
Hard lenses are usually not as comfortable as soft lenses and are not as widely used. However, rigid gas permeable lenses provide sharper vision for people with higher refractive errors or larger degrees of astigmatism.
The majority of people can tolerate contact lenses, but there are some exceptions. Conditions that might prevent an individual from successfully wearing contact lenses include dry eyes, severe allergies, frequent eye infections, or a dusty and dirty work environment.
Individuals who wear any type of contact lens overnight have a greater chance of developing infections in the cornea. In fact, overnight contact lens wearers have a 20-fold higher risk of a serious eye infection compared with wearing contacts during the day and removing and cleaning the lenses at night.