contact the concept of corrective lenses that sit directly on the eyeball green was developed in the ninth century, but it was not until the late 20th century that manufacturing 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 plastic. today, the majority of lenses worn are of two basic types: rigid gas permeable (so-called "hard" lenses) and lenses. best lenses are smaller 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 and less expensive, but can be easily torn. the latest generations of contact are extended and disposable lenses. extended lenses are intended to 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.

contact the concept of corrective lenses that sit directly on the eyeball green was developed in the ninth century, but it was not until the late 20th century that manufacturing 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 plastic. today, the majority of lenses worn are of two basic types: rigid gas permeable (so-called "hard" lenses) and lenses. best lenses are smaller 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 and less expensive, but can be easily torn. the latest generations of contact are extended and disposable lenses. extended lenses are intended to 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.

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 goddess the contacts 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 sfx flexon frames. people at risk of being in accidents that might shatter glass lenses should wear plastic lenses, preferably theatrical polycarbonate.