Contact lenses: What to know before you buy

With contact lenses, you can get excellent vision correction and comfortable fit. But contacts aren't risk-free — especially if you don't clean and store them properly.

Here are some pointers on safe disinfection, storage and handling of contact lenses, followed by a rundown of contact lens types.

Avoiding eye infections

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Anatomy of your eye

Wearing contact lenses increases your risk of corneal infection. Some of the added risk is unavoidable: All types of contact lenses reduce the amount of oxygen that reaches your cornea — the clear tissue that lies over the pupil and iris — and less oxygen can promote infection.

This reduction in corneal oxygen makes proper cleaning and disinfection all the more important. Here are some tips:

• Use multipurpose contact lens solutions with caution. While these combination cleaning-disinfectant-storage solutions are convenient, two brands have been withdrawn from the market because they've been linked to serious eye infections. In 2005 and 2006, 130 contact-lens wearers who regularly used Bausch & Lomb's ReNu with MoistureLoc solution developed Fusarium keratitis, a fungal infection of the cornea, prompting that brand's recall. A year later, in 2007, Advanced Medical Optics voluntarily recalled its Complete MoisturePlus solution, which was implicated in 138 cases of Acanthamoeba keratitis, a parasitic infection of the cornea.
• Choose daily-wear contacts, and take them out before you go to sleep. Infections are more common with extended-wear contacts, worn continuously, than with daily-wear contacts.
• Wash, rinse and dry your hands thoroughly before handling your contacts.
• Follow your eye-care professional's instructions for taking care of your lenses. Make sure you use lens-care products formulated for the type of lenses you wear.
• Replace your contact lenses as recommended. If one or both lenses bother you before you're due to replace them, get them checked or try a new set — if you have a supply.

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Types of contact lenses

Contact lenses are made of many different types of plastic, but in general, they fall into two main groups: soft contact lenses and gas-permeable contact lenses.

Soft contact lenses
These thin, gel-like lenses conform to the shape of your eye. They're more flexible than gas-permeable contact lenses, so they're more comfortable and easier to get used to.

Types of soft contact lenses include:

• Daily-wear contact lenses. Four out of five people who wear contact lenses choose daily-wear, which are lenses you typically insert every morning and remove every night. They should not be worn during sleep. Properly cleaned and stored, one pair of daily-wear lenses should last up to one year.
• Disposable contact lenses. These lenses are designed for short-term use during waking hours. Depending on their composition, disposable lenses may need replacement every day — you throw them away after wearing them once — or at longer intervals, up to three months. Most brands are good to wear for two weeks.
• Extended-wear contact lenses. Because they're designed to provide adequate oxygen to your cornea even while you sleep, you can wear these lenses continuously — for up to seven days with standard extended-wear contact lenses, and all the way up to 30 days with lenses made of superpermeable silicone hydrogel. The 30-day lenses are somewhat stiffer and less comfortable than the seven-day lenses. Also, 30-day lenses may get scratched more easily and have less clarity than do lenses removed every seven days.

Gas-permeable contact lenses
Gas-permeable contact lenses are generally made of harder plastic materials that don't contain water. Although they aren't as flexible as soft contacts, gas-permeable lenses allow more oxygen to pass through to the cornea than do soft lenses, reducing the risk of corneal irritations.

Gas-permeable lenses can correct a wide range of vision problems, including astigmatism, which is a type of blurred vision caused by an irregularly shaped cornea. After a short period of adaptation, most people can wear gas-permeable lenses comfortably. Gas-permeable lenses are easy to care for, and they're less likely to cause infection and more durable than soft lenses.

Gas-permeable lenses need to be replaced less frequently than do soft contact lenses and may be worn, on average, for two to three years.

Pros and cons of soft vs. gas-permeable contact lenses

How do you choose between soft contact lenses and rigid gas-permeable contact lenses? Here's a look at the advantages and disadvantages of each.

Hybrid contact lenses
Hybrid contact lenses, which feature a gas-permeable center surrounded by a soft outer ring, hit the market in 2006. These lenses offer the combined benefits of better visual acuity associated with gas-permeable contact lenses and greater comfort associated soft contact lenses. Hybrid contact lenses may be an option for people needing vision correction for problems such as astigmatism, keratoconus or presbyopia.

Getting the right fit

If you decide you want contact lenses, have a thorough eye examination and fitting by an experienced professional. Follow-up exams are important to monitor any changes to your vision and to update your prescription. If you're a regular contact lens wearer, see your doctor annually for an eye exam and a contact lens evaluation — more often if you have any problems.

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