A process for the treatment of a soft contact lens, to increase its resistance to the deposition thereon and diffusion and accumulation therein of substances which will promote its clouding and discoloration in use, and to improve its mechanical strength, includes treating a hydroxyl group-containing acrylic ester soft contact lens or replica with an organic acid anhydride for a sufficient period of time to treat at least a portion of polymer molecules on the outer surfaces, e.g. by esterifying hydroxyl groups on the molecules and facilitating extraction of organic-type impurities. The process is optionally performed in the presence of a medium which partially swells the surface regions of the lens or replica prior to or during the process.