For some people glasses are a pain. They slide around on your nose. They fly off your face when you're playing hard. They attract dirt like a kid. They need windshield wipers when it rains. They fog up when you come in from the cold. And you're almost certain that someday a mishap is going to fold your $400 pair of glasses into an abstract work of art that's not worth a nickel.
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| How Do Contact Lenses Correct Vision |
Contact lenses are a nice alternative. If you want to wear contacts, the odds are you can. Nine out of 10 people who want to give them a try are able to wear them, including older adults.
Years ago contacts were mainly for nearsighted teens and young adults whose eyes could easily adapt to the hard lenses that were at that time the only type available. But since the arrival of soft lenses, which are more comfortable and easier to use, contacts have become more popular with a wider variety of people. About 30 million Americans now wear them. Another reason for the growing popularity of contacts is that now they can correct vision problems that before could be corrected only with eyeglasses. You can even get contact bifocals.
Types of contact lenses
Contact lenses have come a long way since Leonardo da Vinci drew his first sketch of them about 500 years ago, and since a Swiss scientist in 1887 manufactured the first pair out of glass - which, by the way, the human eye couldn't tolerate. It wasn't until the coming of plastics in the 1940s that contacts became practical. The hard contacts developed back then were well tolerated, and the type of plastic used in those lenses is still used today.
Hard contacts. Only about 1 percent of contact wearers still use the original style of hard contacts. These lenses provide sharp vision, but they don't allow oxygen to pass through them to nourish your cornea as well as other types of contacts do. Oxygen gets to the cornea only by going around hard contact lenses. These lenses are also the most difficult to get used to. When you first start using them, you may feel them in your eyes, but your eyes will adapt after several days. Still some people prefer them because hard lenses are the most durable. If you take good care of them, they can last a decade or more.
Rigid gas-permeable lenses. Developed in the late 1970s, rigid gas-permeable lenses are slightly flexible hard contacts that are more porous to oxygen. They offer excellent correction for a wide range of vision problems. They're usually easy to adapt to, comfortable and more durable than soft lenses. For some people "gas-perms" may provide sharper vision than soft contacts. But they have several drawbacks. You have to wear them regularly to keep your eyes used to them. They can slip off the cornea and even pop out of your eye more easily than soft contacts do. And, as with original hard lenses, it's easier for dust to get under them and irritate your eyes.
Soft contacts. Doctors sometimes call soft contacts hydrogels because they hold water, which is what makes them so soft and comfortable. The water content varies from about one-third to three-fourths of the lens, depending on the material. Unlike hard lenses, soft contacts allow oxygen to pass through the plastic and nourish your cornea. Softer than rigid gas-permeable lenses, these contacts are even more comfortable and easier to adjust to. But they aren't nearly as durable. Several kinds are available:
Daily wear, or conventional. Daily wear, or conventional, contacts are thin plastic lenses that conform to the shape of your eye. As the name implies, they're designed to be worn when you are awake and taken out before you go to sleep. They're not something you should wear overnight. You'll need to clean them every day you wear them and replace them each year.
Besides being comfortable and easy to get used to, daily wear lenses, like all soft lenses, tend to stay in place. That makes them a good choice if you're involved in sports or are otherwise very active. Like other soft contacts, they can't correct some common vision problems, such as a high degree of astigmatism.
Disposable, or frequent-replacement. Disposable, or frequent-replacement, lenses are thinner and more porous to oxygen than daily wear lenses, which makes them even more comfortable. As the name suggests, disposables are usually worn for a short time and then discarded. Some are designed to be worn only 1 day.
Others can be worn during your waking hours for a week or two. Still others can be worn 1 to 3 months. It depends on the design and material and how well you take care of them.
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| How Do Contact Lenses Correct Vision |
Like other soft lenses, disposables can be harder to handle than hard contacts and can be torn if you handle them too roughly. Also, any lenses that you use for longer than a day need to be cleaned every day. They are prone to surface buildup.
Extended wear. Extended wear lenses are usually disposable and are designed to be worn for more than 24 hours without having to remove them. Because these lenses are designed to provide adequate oxygen to your cornea even while you're sleeping, they're approved for up to 7 days of wear. But most eye doctors don't recommend extended wear contact lenses because regardless of the material they're made of, your eyes receive less oxygen when you sleep while wearing contacts. Furthermore these lenses put you at greater risk of a serious eye infection because the buildup of bacteria on them increases dramatically if you wear them overnight. To find out more, you can check out How Do Contact Lenses Correct Vision.