|
|
They can be worn up to a week. Daily wear lenses are made of plastic that is permeable to oxygen and absorbs water; therefore, they are soft and flexible. contacts These lenses eyewear must be removed and cleaned each night, and they do not correct all contacts vision problems. lenses eyewear are easier to get used to than rigid lenses, but are more prone to tears and do not last as long. Extended-wear contacts lenses are highly permeable to oxygen, are flexible by virtue of their ability to absorb water, and can usually be worn for up to one week. They do not correct all vision problems. There is more of a risk of infection with extended-wear lenses than with daily-wear lenses. Extended-wear eyewear disposable lenses are lenses worn continually for up to six days and then discarded, with no need for cleaning. contact contacts The concept of corrective lenses that sit directly on the eyeball was developed in the ninth century, eyewear but it was not until the late 20th century that manufacturing contacts and grinding techniques for contact were perfected. Originally contact were made of glass, then later of hard plastic, and still later of flexible, highly oxygen-permeable soft eyewear plastic. Today, the majority of lenses worn are of two basic types: contacts and eyewear rigid gas permeable (so-called "hard" lenses) and lenses. best lenses are smaller contacts and more durable, but require a longer period of adjustment for the wearer. Hard contact can correct some vision problems, like astigmatism, that the lenses cannot. The lenses are slightly larger than best lenses. They are more comfortable eyewear and less expensive, but can be easily torn. The latest generations of contact are extended and disposable lenses. extended contacts lenses are intended to eyewear be worn for several weeks at a time, while disposable lenses are thrown away every day or every few weeks, or in the newest versions, every day. The primary drawback to wearing contact, especially for children, is the requirement that they be cleaned and disinfected daily in order to prevent an infection, which could result in permanent damage to the eye. Careful contacts choice of lenses and consistent lens care will minimize the risk of infection. Wearers of best lenses are the least prone to infection but the eyewear lenses are much less comfortable, more expensive, contacts and eyewear and can pop out of the eye more easily than lenses. Daily wear lenses put the wearer at a slightly higher risk of infection because they absorb more external liquids and airborne contaminants.
|