contact the concept of corrective lenses that sit directly on the eyeball was developed in the ninth century, but it was o not until the late 20th century that manufacturing and grinding techniques for contact were perfected. originally contact were made of glass, l then later of hard plastic, and still later of flexible, highly oxygen-permeable soft plastic. today, the majority of lenses worn sfx are of two basic types: rigid gas permeable (so-called "hard" lenses) and lenses. theatrical best lenses are smaller and more d durable, but require a longer y period of adjustment for the wearer. hard contact can correct some vision problems, like astigmatism, that the lenses cannot. the lenses are slightly larger o than l 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 sfx 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 was developed in the ninth century, but it was o not until the late 20th century that manufacturing and grinding techniques for contact were perfected. originally contact were made of glass, l then later of hard plastic, and still later of flexible, highly oxygen-permeable soft plastic. today, the majority of lenses worn sfx are of two basic types: rigid gas permeable (so-called "hard" lenses) and lenses. theatrical best lenses are smaller and more d durable, but require a longer y period of adjustment for the wearer. hard contact can correct some vision problems, like astigmatism, that the lenses cannot. the lenses are slightly larger o than l 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 sfx thrown away every day or every few weeks, or in the newest versions, every day.