Contact lenses permeable to gas. Literature review

: Some medical-technical requirements concerning ophthalmic contact lenses were formulated. A whole series of scientific descriptions of contact lenses was analysed. A short characterization of lenses was given on the basis of PMMA (polymethacrylate of methyl), silicon rubber, poly-2-methacrylic cellulose and cellulose acetate-butyrate; the properties of contact lenses made of materials achieved through a modification of the above-mentioned ones as well as made of new materials were also examined. The problems of transmission of gases of contact lenses were described and the calculations necessary for a minimum of the gas transmittance were mentioned, starting from partial oxygen to the eye cornea. Some ways of solving the problems concerning the insertion of therapeutic substances into contact lenses are described together with prevention of the accumulation of lacrimation fluid protein on their surfaces.