Improvements in contact lenses

eye2eye · #1 (**permalink**) 10-07-2008, 06:18 PM

Improvements in contact lenses have made them more comfortable and easier to wear. In the United States, millions of people wear contact lenses, and most wear soft lenses. For these people, contact lenses offer a relatively safe and effective way of correcting vision problems.

Several types of contact lenses are available to correct nearsightedness. contact lenses are needed after cataract surgery if an artificial lens cannot be implanted in the eye.

Hard (rigid) lenses
Conventional hard (polymethyl methacrylate, or PMMA) lenses are made of a fairly stiff plastic. They correct vision with no distortion, but they are the least comfortable type of contact lens.
Rigid gas-permeable (RGP) lenses are more comfortable than conventional hard lenses. Some gas-permeable lenses are designed to be worn overnight and for up to 7 days.
Soft lenses
Daily-wear lenses are removed and cleaned at night and reinserted in the morning.
Extended-wear lenses can be worn for up to a week at a time, day and night. But extended use may be uncomfortable, and it increases the risk of damaging the eye.
Disposable lenses (daily and extended-wear) may be worn for up to several weeks and then discarded.
What To Expect After Treatment
With most hard contact lenses, there will be a 2- to 4-week break-in period during which you wear the lenses for increasingly longer periods of time each day. Soft contact lenses usually take less time to break in.

Why It Is Done
contact lenses can correct nearsightedness (myopia), farsightedness (hyperopia), astigmatism, and presbyopia. Lenses that correct astigmatism are called toric lenses. They may need to be custom-made and may be more expensive than ordinary contact lenses.

contact lenses may be used by people who have had surgery for cataracts if the natural lens of the eye was removed. They may also be used to treat eye diseases, such as keratoconus or damage to the cornea caused by injury or infection.

Most people choose to wear contacts because of the convenience and because they prefer the way they look without eyeglasses.

Bifocal contact lenses have been developed for people who have both nearsightedness and presbyopia. Bifocal lenses provide correction for both near and distance vision on each lens.

If bifocal contact lenses will not work for you, your doctor may recommend monovision. With monovision, you wear a contact lens that corrects for near vision in one eye and a lens that corrects for distance vision in the other eye. Most people who try monovision can adjust to it. Monovision has some drawbacks, though. Each eye must work more independently, making good binocular vision difficult, which can cause problems with depth perception. You may have to adjust your gaze more often to allow one eye or the other to see properly.

In other cases, your doctor may recommend using reading glasses in combination with contact lenses that correct for distance vision.

People who are generally well-suited to wearing contact lenses (hard or soft) include:

People who have significant trouble seeing things at a distance and need vision correction all the time. People who wear eyeglasses only part of the time are less likely to wear contacts successfully.
Those with strong motivation. You have to be willing to tolerate minor discomfort during the break-in period and to learn and use proper methods of storing and handling your lenses.
Contacts are preferred over glasses for people who perform work or play sports in which glasses are inconvenient or dangerous.

contact lenses are not a good choice for you if you:

Are not able or are not willing to care for the lenses properly.
Would have a hard time handling the lenses (for example, if you have severe arthritis in your hands or another problem that would make it hard for you to insert, remove, and clean the lenses).
Have certain medical conditions such as diabetes or hyperthyroidism. Allergies, asthma, and other chronic respiratory disorders may make it difficult to wear contacts.
Have dry eyes or problems with the cornea. People who have Sjögren's syndrome (a condition that causes a lack of tears and dry eyes) often are not able to wear contacts. People who have chronic or recurrent infections or sores on the cornea cannot wear contact lenses.
Have a job that exposes you to particles, chemical fumes, or other vapors that may be absorbed by or stick to the lenses (such as dust and dirt, paint, spray chemicals, or hair spray).
Infants and children
Infants and children usually do not wear contact lenses, except to treat some medical conditions. Many teenagers wear contacts, but they and their parents must accept the need for frequent changes in the prescription until their eyes stop changing in the late teens or early 20s.

How Well It Works
Almost everyone who is nearsighted can be fitted with contact lenses. Some types work better than others to correct specific problems.

Rigid gas-permeable lenses may be the best choice for people who have both nearsightedness and astigmatism.
Some people cannot tolerate hard lenses. Soft lenses that correct both nearsightedness and astigmatism are available. Soft contact lenses tend to be more comfortable than hard lenses, but hard lenses usually provide sharper vision.
Some people may choose good (rather than optimal) vision correction in exchange for greater comfort. People with severe nearsightedness or both nearsightedness and astigmatism may get the best vision correction from gas-permeable lenses, but they may have satisfactory correction with soft lenses, which are generally more comfortable.

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Improvements in contact lenses

Contact Lenses