[The meaning of oxygen permeability in different materials for optimalization of contact lenses function].

Contact lenses are a modern method of refraction defects correction. Polymers of different kind are a basic material for contact lenses. Only with such a sophisticated material can a functional, yet safe for the eye, contact lens be made. Contact lens must be oxygen-permeable to provide nutrition for cornea which has no own vascular net. In the past decade hydrogel lenses are being replaced with silicone-hydrogels. A new generation of contact lenses does not disturb the physiology of a cornea as much as the old one. Since the introduction of silicone-hydrogel lenses much less side effects have been reported. They can also be used continuously with less risk, over longer period of time. Traditional measures such as oxygen permeability and transmissibility seem inadequate with silicone-hydrogel lenses. Therefore a new measure, an oxygen flux, has been introduced. It is more physiological and more suitable in higher oxygen transfer range. It refers to quantity of oxygen reaching the surface of a cornea.