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when used with care and proper supervision. They can offer a good alternative to eyeglasses, depending on your eyes and your lifestyle.
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:
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. Rigid contacts were the first lenses; they were developed in the 1960s. 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. Newer rigid lenses made of plastics 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. SOFT LENSES TABLE More than 75% of contact lens wearers in the United States use soft 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. Soft daily-wear lenses should never be used as extended-wear lenses. Extended wear lenses can be used as daily-wear lenses. 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 reactions and deposit formation. Toric lenses correct moderate astigmatism. They are available in both rigid and soft materials.
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.
Rigid lenses that are not gas permeable are more likely to scratch the cornea if the lens does not fit properly or 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 nongas-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 infections. 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 your 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:
The health of your eyes should be your
main concern. An ophthalmologist is the physician specialist
who can help you decide whether contact lenses are right for
you. Are contacts for you? Whether or not contact lenses are a good choice for you depends on: If you have any additional questions or would like further information, ask your ophthalmologist.
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