Evaluation of polyvinyl alcohol hydrogel as a soft contact lens material.

We prepared a transparent polyvinyl alcohol (PVA) hydrogel from a PVA solution in a mixed solvent consisting of water and a water-miscible organic solvent by cooling. The physical properties of the hydrogel were evaluated in various mixed solvents and compared with those of commercially available soft contact lens materials, such as polyhydroxyethyl methacrylate (PHEMA) and copolymers of methylmethycrylate (MMA) and N-vinyl pyrrolidone (N-VP). The PVA hydrogel showed higher tensile strength and elongation before breaking than did the other materials. Also, the PVA hydrogel was comparable in its high water content and its oxygen permeability with the MMA/VP copolymers. The protein adsorption of the PVA hydrogel was much lower than that of the other materials. Soft contact lenses of PVA hydrogel were applied to rabbit eyes for 12 weeks. The effects of the lenses on the cornea were studied by biomicroscopy, ultrasonic pachymetry, and histopathologic examination. No abnormal findings were noted, suggesting that the PVA hydrogel may be promising as a new material for use in soft contact lenses.