Contact lens wearers have known for years that contacts in their eyes need to be removed before nodding off to sleep. It’s just one of those accepted things in life—you don’t sleep with contact lenses in. But times have changed as improvements to extended wear contact lenses are attracting more and more users.

While disposable and daily wear contacts are generally removed at night, people with extended wear contacts can leave the lenses in for up to 30 days at a time. Extended wear lenses are more oxygen permeable—basically meaning that they “breathe” better—than daily-wear lenses, which make them safer for sleeping with.

Extended wear contacts may or may not be for you. Here are a few points to consider:

Extended wear contact lenses, such as Air Optix, by Ciba Vision can be worn overnight, or with continuous wear ranging from 1-6 nights, or even up to 30 days. These soft contact lenses are made of flexible plastics that allow oxygen to pass through to the cornea. How long a person wears them comfortably depends on the type of lens and a person’s tolerance for overnight wear.

But even with newer lens like Air Optix, some eye doctors feel that extended wear contact lens users are at risk of infections from leaving them in too long. For the majority of users who have difficulty with extended wear lenses, the problem is not that they develop infections, but that the lenses start to bother them far sooner than their 30-day “expiration date”. As a result, people often change their lenses once a week, which in part defeats the purpose of the extended wear promise.

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Extended wear contact lenses are popular with young people due primarily to their longer wearing times and low-maintenance.

However, because of popular movies like the Twilight series, some young people are starting to buy decorative extended wear contact lenses without a proper prescription in order to change the color of their eyes. This has increased the numbers of young people wearing contact lenses, and has caused concern among eye groups for inherent dangers in long-term wear.

The American Optometric Association noted that this use of non-corrective novelty appears to be growing, “particularly among teenagers and pre-teens”. While it’s against federal law to sell contact lenses without a prescription in the U.S., that hasn’t stopped merchants from offering these decorative lenses in shopping malls, costume shops and other specialty retailers, according to the AOA Advocacy Group.

Generally, using extended wear contact lenses is a decision that must be made by teenagers, their parents and an eye-care professional. Teenagers are usually self-conscious about their appearance, so many feel that wearing contact lenses is preferable to wearing glasses. They’re also an advantage for active teens who play contact sports like basketball, soccer, and football.

Contact lenses vary in price, depending on type of lens, length of wear, brand, and number of lenses per package. To get a feel for costs, ask your eye care professional for estimates on various brands or search the Web for the best prices. Definitely take into account the cost of the extras. If you choose to use daily disposable contacts, your costs will be lower, as they don’t require any cleaning supplies or containers. Disposables cost about $1 per day. These are an attractive option for eyeglass wearers who want to leave their glasses at home on date night.

During your contact lens fitting and follow-up, your eye doctor will judge whether you’re able to wear overnight or extended wear contacts, and offer suggestions on how often to change them. You’ll also need a compatible eye solution for your lens type, which can often spell the difference between red and irritated, or safe eyes. Never make this decision on your own!