Contact lenses are thin, curved plastic disks designed to cover the cornea, the clear front covering of the eye. Contacts cling to the film of tears over the cornea because of surface tension, the same force that causes a drop of water to cling to the side of a glass.

Contact lenses are used to correct the same conditions that eyeglasses correct:

Myopia (nearsightedness)
Hyperopia (farsightedness)
Astigmatism (distorted vision)
Presbyopia (trouble reading with age)

Special tinted contacts can be used to change the color of the eyes to various degrees. Contact lenses are sometimes used therapeutically in eye diseases where an uneven cornea blurs vision, such as keratoconus or scarring. They are also sometimes used for corneal abrasions to assist in healing.


PPMA lenses
Rigid contacts were the first lenses; they were developed in the 1960's. They are made of a type of plastic called PMMA, which is very durable, but does not allow oxygen in the air to directly reach the cornea. When the eye blinks, the lens moves, which allows the oxygen dissolved in the tears to reach the cornea. While rigid lenses are probably the least comfortable type of contacts to wear, some users prefer them for their durability and lower cost.

Gas-permeable lenses
Newer rigid lenses made of plastic combined with other materials, such as silicone and fluoropolymers, allow oxygen in the air to pass directly through the lens. They are called gas permeable. Gas-permeable lenses are less durable than conventional rigid lenses but are more comfortable. Some gas-permeable lenses are extended wear and may be worn overnight for up to seven days.

Soft contact lenses
These lenses are made of plastic materials that incorporate water. The water makes them soft and flexible, as well as allowing oxygen to reach the cornea. More than 75% of contact lens wearers in the United States use soft contact lenses. Some soft contact lenses are extended-wear lenses, which means they are designed to be left in the eye overnight. It is recommended that extended-wear lenses be removed weekly, at a minimum, for thorough cleaning and disinfection. The FDA has newly approved a contact lens for wear up to 30 days. Soft daily wear lenses should never be used as extended-wear lenses. Extended-wear lenses can be used as daily-wear lenses. Studies have shown increased risk of corneal infections associated with extended wear contact lens use.

Disposable soft contact lenses
Disposable lenses for daily or extended wear have recently become available. The lenses are discarded and replaced each week. These lenses are convenient and may reduce the chance of allergic reaction and deposit formation.
Toric contact lenses Toric lenses correct moderate astigmatism. They are available in both rigid and soft materials.

Bifocal contact lenses
These lenses correct both reading and distance vision. They can eliminate the need for reading glasses.


When comparing the price of contact lenses, it's important to consider what services are included. Does the fitting include a thorough eye examination and follow-up? Can you exchange lenses during the initial fitting, and is insurance for lost lenses available? If you need treatment for an eye condition not directly related to the contact lenses, such as inflamed eyelids or dry eyes, there may be additional charges.

What are the risks of wearing contact lenses?
Rigid lenses that are not gas permeable are more likely to scratch the cornea if the lens does not fit properly of if the lens is worn while sleeping. They are also more likely to slide off the cornea and become hidden under the lid.

Rigid lenses traditionally had a reputation for "popping out" of the eye. New lens designs have minimized the chance of losing a contact even during vigorous exercise. Rigid gas-permeable lenses may allow more protein build-up than rigid non-gas-permeable lenses. Protein build-up results in discomfort, blurring and intolerance to the lenses. You will need special cleaning solutions to dissolve the protein.

Daily-wear lenses should never be worn as extended-wear lenses. Misuse can lead to temporary and even permanent damage to the cornea. People who wear any type of lens overnight have a greater chance of developing infections of the cornea. These infections are often due to poor cleaning and lens care.


Contact lenses must be properly cleaned and disinfected when you remove them to kill germs and prevent infection. At the time you insert your contact lenses, you should thoroughly rinse the case with warm water and allow it to dry. All contact lens cases need frequent cleaning, including disposable lens cases.

Soft extended-wear contacts are the most likely to have protein build-up and cause lens-related allergies. Soft daily-wear lenses are less likely to create problems. Rigid gas-permeable or disposable lenses may be good choices for someone with allergies.

Homemade saline solutions have been linked to serious eye infections and should never be used.
Any eye drops, even nonprescription ones, can interact with all types of contact lenses. Check with you ophthalmologist before you use any eye drops.


Most people who need vision correction can wear contact lenses, but there are some exceptions.
Some of the conditions that might keep you from wearing contact lenses are:

Frequent eye infections
Severe allergies
Dry eyes (improper tear film)
A work environment that is very dusty or dirty
Inability to handle and care for the lenses properly

The health of you eyes should be you main concern. An ophthalmologist is the physician specialist who can help you decide whether contact lenses are right for you.