Paraperm® O2 (pasifocon A) rigid gas permeable contact lenses for daily wear are available as lathe cut or molded firm contact lenses with spherical, aspheric, bifocal or toric anterior and/or posterior; or, bitoric surfaces in clear and tinted versions. The posterior curve is selected so as to properly fit an individual eye and the anterior curve is selected to provide the necessary optical power to correct refractive error. A peripheral curve system on the posterior surface allows tear exchange between the lens and the cornea.The Paraperm® O2 rigid gas permeable contact lens material is a thermoset copolymer derived from siloxane and methylmethacrylate.The Paraperm® O2 rigid gas permeable tinted lenses offer a handling aid for locating the lens.
A rigid ophthalmic lens intended to be worn directly against the cornea of the eye to correct refractive vision conditions (e.g., myopia, hyperopia, astigmatism, presbyopia); it is designed to be removed prior to sleeping each night. The device is made of various materials (e.g., cellulose acetate butyrate, polyacrylate-silicone, silicone elastomers) whose main polymer molecules generally do not absorb or attract water but permit diffusion of oxygen (O2) to the ocular surface. The lens may last for years and is a reusable device.