This is the third column in a series about vision correction.

There are three basic ways to correct faulty vision: eyeglasses, contact lenses or surgery. In this column, I'll cover contacts.

There are two basic kinds of contact lenses soft and hard.

Soft lenses, which are thin and gel-like, are the most popular of the two types of contacts. They come in many varieties and they are very comfortable. I never felt them in my eyes. The following are some choices in soft lenses:

Daily-wear lenses are removed when you go to sleep. They are the least expensive of the soft lenses.

Extended-wear lenses can be worn when you sleep. They are removed at least once a week to be cleaned and disinfected. There is a greater risk of eye infections when you wear contacts overnight.

Disposable-wear lenses are the most convenient of the contacts. They are removed nightly and replaced on a daily, weekly or monthly basis. These are the most expensive of the contact lenses.

If you replace disposables every day, you always have clean, flawless lenses that produce sharp vision. And you don't have to deal with maintenance. These are enormous advantages.

Hard contacts today are rigid, gas-permeable lenses (RGP). Hard contacts allow oxygen to flow through the lenses to the cornea. The cornea is the transparent cover over the pupil in the center of the eye.

RGP lenses may be the better choice over soft lenses if you have astigmatism, which is caused by an uneven curvature of the eye's surface.

There are soft contact lenses called torics that can correct astigmatism, but not always as well as RGPs can.

RGPs are also preferable if you have allergies or tend to form protein deposits on contact lenses.

You can get multifocal contact lenses both hard and soft. They can correct nearsightedness, farsightedness and astigmatism in combination with presbyopia, which is the natural condition of aging that makes it more difficult to focus on near objects.

The major downside of contact lenses is taking care of them.

Lenses that are not properly cleaned and disinfected increase the risk of eye infection. Any lens that is removed from the eye needs to be cleaned and disinfected before it is reinserted.

The following are some guidelines for care of contact lenses from the American Academy of Ophthalmology:

Ÿ Before handling contact lenses, wash your hands with soap and water, then rinse and dry them with a lint-free towel.

Ÿ Minimize contact with water, including removing lenses before going swimming or in a hot tub.

Ÿ Contact lenses should not be rinsed with or stored in water (tap or sterile water).

Ÿ Do not put your lenses in your mouth to wet them. Saliva is not a sterile solution.

Ÿ Do not use saline solution and rewetting drops to disinfect lenses. Neither is an effective or approved disinfectant.

Ÿ Wear and replace contact lenses according to the schedule prescribed by your eye care professional.

Ÿ Follow specific contact lens cleaning and storage guidelines from your eye care professional and the solution manufacturer.

Ÿ During cleaning, rub your contact lenses with your fingers, then rinse the lenses with solution before soaking them.

This "rub and rinse" method is considered by some experts to be a superior method of cleaning, even if the solution you are using is a "no-rub" variety.

Ÿ Rinse the contact lens case with fresh solution not water. Then leave the empty case open to air dry.

Ÿ Keep the contact lens case clean and replace it regularly, at least every three months.

Ÿ Lens cases can be a source of contamination and infection. Do not use cracked or damaged lens cases

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