What are contact lenses?
Contact lenses are placed in your eyes to help correct vision problems. They are small, curved pieces of plastic shaped to fit your eyes. Contact lenses float on top of a thin layer of tears on the cornea, which is the clear outer layer on the front of the eye. Contact lenses can correct most of the vision problems that glasses correct. They can also correct some problems that glasses cannot.
When are they used?
Contact lenses may be more practical than eyeglasses if you play sports or work at jobs where glasses could get in the way. Also, contacts give better side vision than glasses do. You may choose contact lenses simply because you prefer the way you look without wearing glasses.
Contact lenses may provide better vision than glasses if you:
- Have had cataracts removed
- Are very nearsighted or farsighted
- Have corneas damaged by disease or injury
You may find it hard to wear contact lenses if you have:
- Very irritated eyes from allergies or exposure to dust or chemicals at your job
- An overactive thyroid gland, uncontrolled diabetes, a tremor, or severe arthritis in your hands
- Dry eyes because of pregnancy, birth control pills, diuretics, antihistamines, or decongestants
- An eye disease that affects the surface of your eye
What are the main types of contact lenses?
Gas permeable contact lenses
The plastic used for gas permeable (GP) lenses lets oxygen reach the cornea. GP lenses may be called hard lenses because they are stiffer than soft contact lenses.
GP lenses have some advantages over soft lenses:
- They often correct vision better than soft lenses do, especially if your cornea is scarred or has an uneven shape.
- Allergic reactions to lens care solutions are less common. Unlike soft lenses, GP lenses do not absorb liquids.
- GP contacts are easier to clean than soft contacts, and GP cleaning solutions cost less.
- GP lenses cost less than soft lenses because they last longer and can be polished and reground if you scratch or outgrow them.
The main disadvantage to GP lenses is that they are harder to get used to than soft lenses.
Soft contact lenses
Soft lenses are made of material that absorbs fluid. Soft lenses are very flexible. They are usually more comfortable than GP lenses, and you can adjust to wearing them more easily. They are also less likely to fall out than the GP lenses. Most people who wear contacts wear soft contact lenses.
The disadvantages of soft contact lenses include:
- They are harder to put in than GP lenses.
- Soft lenses must be cleaned and sterilized carefully.
- Soft lenses can be more expensive than GP lenses and need to be replaced more often. Also, you need to buy several cleaning and storing solutions for soft lenses.
- Wearers of soft contact lenses may be more likely to get eye infections than wearers of GP lenses.
Daily-wear soft contact lenses must be removed and cleaned every night. Daily disposable contact lenses should be thrown away after wearing them for one day. Extended-wear soft contact lenses are very thin but contain a lot of water, which lets oxygen reach the eyeball even if you wear them for long periods. Some types can be worn overnight or for more than 1 day. However, your eye care provider may advise that you not wear your contacts when you sleep. Wearing the lenses too long greatly increases the risk of eye irritation or serious eye infection.
Disposable contact lenses
Disposable contact lenses are lenses that you wear for a short period of time and then throw away and replace with new ones.
There are different types of disposable contacts. Some are used for one day only and then thrown away. You put in new lenses every morning and discard them at night. Others are worn each day, removed and disinfected each night, and discarded after 1 week to 3 months, depending on the specific lens. People may try to wear the lenses longer than the recommended time or reuse the lens to save money. Wearing the lenses too long or reusing them greatly increases the risk of eye irritation or serious eye infection.
The advantages of disposable lenses are:
- They are comfortable, and if a lens is lost or torn, you almost always have an extra lens on hand. You do not have to wait for a new contact to be ordered.
- They are easier to care for than regular soft contacts. When worn properly, the lenses are replaced before proteins and other deposits can build up on them. This can help prevent eye problems.
- They can be a good choice if you only want to wear contacts for special events or sports, rather than wearing contacts all the time.
The main disadvantage is that disposable lenses cost more to purchase than other kinds of contact lenses.
Bifocal contact lenses
Bifocal contact lenses have both your distance prescription and your reading prescription in each lens. They are available as gas permeable or soft lenses, and as daily wear or extended wear types. You may need to try bifocal contact lenses to decide if they are right for you.
How can I get contact lenses?
You need a thorough eye exam by an eye doctor who will:
- Measure the curvature of the cornea, check the position of your eyelids, and check the health of the surface of your eye and eyelids.
- Suggest either gas permeable or soft lenses.
- Teach you how to put in and take out your lenses.
- Review with you how to best care for your lenses.
- Check your eyes regularly after you start wearing your lenses.
Slight discomfort when you first start wearing contact lenses is normal. If you have any pain in your eyes, see your eye care provider. You should have checkups of your eyes and lenses 1 week, 2 weeks, 1 month, 6 months, and 1 year after you first get them. If you have any problems, talk about them with your eye care provider.
Reviewed for medical accuracy by faculty at the Wilmer Eye Institute at Johns Hopkins. Web site: http://www.hopkinsmedicine.org/wilmer/
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