about contacts

Originally, hard contact were made of a material called PMMA. Although still available, the more common types of contact are listed below:Rigid gas-permeable (RGP) daily-wear about lenses are made of plastic that does not absorb water but allows contacts oxygen to get from the atmosphere to the cornea. (This is important because the cornea has no blood supply and needs to get its oxygen from the atmosphere about through the film of tears that moves beneath contacts the lens.) They must be removed and cleaned each night. Rigid about gas-permeable (RGP) extended-wear lenses are made from plastic that also does not absorb water but is more permeable to oxygen than the plastic used for daily-wear contacts lenses.

Simultaneous lenses bring distant and near objects into focus at the same time. about 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 contacts and about and contacts 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 about Designed for mild nearsightedness, KeraVision Intacs are placed contacts in the periphery of the cornea by an ophthalmic surgeon. Made of polymer, a type of hard plastic, about they require no maintenance and can be surgically removed. The contacts outpatient procedure has a 97-percent success rate of 20/40 vision or better.