Simultaneous lenses bring distant and near objects into focus at the same time. The center of the lens corrects distance vision; the outer part corrects near vision. * Segmented lenses correct distance vision in the top half and near vision in the bottom half.Monovision An alternative to bifocal contacts, monovision lenses correct distance vision in one eye and near vision in the other. Modified monovision allows wearers to put a bifocal lens in one eye and a single-vision lens in the other.Implants Designed for mild nearsightedness, KeraVision Intacs are placed in the periphery of the cornea by an ophthalmic surgeon. Made of polymer, a type of hard plastic, they require no maintenance and can be surgically removed. The outpatient procedure has a 97-percent success rate of 20/40 vision or better.

Eye glasses and contact lenseses and contact are devices that correct refractive errors in vision. lenses lenses are mounted in frames worn on the face, sitting mostly on the ears and nose, so that the lenses are positioned in front of the eyes. contact appear to be worn in direct contact with the cornea, but they actually float on a layer of tears that separates them from the cornea.PurposeThe purpose of lenseses and contact is to correct or improve the vision of people with nearsightedness (myopia), farsightedness (hyperopia), presbyopia, and astigmatism.Precautions People allergic to certain plastics should not wear contact or lenses frames or lenses manufactured from that type of plastic. People allergic to nickel should not wear Flexon frames. People at risk of being in accidents that might shatter glass lenses should wear plastic lenses, preferably polycarbonate.

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.