contact lens problem - soft perm contacts

Another contact type of multifocal, a trifocal, has an area in-between that corrects for intermediate distances (usually about 28 in). lens Conventional bifocals and trifocals have visible lines between the areas of different correction; however, lenses where the correction gradually changes from one area to the other, without visible lines, have been available since the 1970s. problem Such lenses are contact sometimes called progressives or no-line bifocals.To be suitable for lenses lenses, a material must be transparent, without bubbles, and have a high index of refraction. The greater the index of refraction, the thinner the lens can be. Lenses are made from either glass or plastic (hard resin). The advantage of plastic is that it is lightweight and more impact resistant than glass. The advantage of glass is that it is scratch resistant and provides the clearest possible vision.

extended lenses in particular pose a much greater risk than daily wear lenses. Though extended-wear lenses are extremely thin and allow some oxygen--necessary for healthy eyes--to reach the cornea, they are worn continuously, including at night while the eyelid is closed. Bacteria can easily grow more easily under these conditions. Twenty-one in 1,000 extended lens wearers develop infections as opposed to 4 in 1,000 daily soft lens wearers. To reduce this risk, eye care professionals now recommend removing extended lenses at night. In addition, newer versions of extended lenses being developed may offer increased oxygen exchange and pose less risk. Disposable lenses may also help to prevent infection, since the wearer is guaranteed a clean pair of lenses every few weeks or every day.