well as the preferred concentration of ester in the polymerization reaction mixture is described in detail in u s pat no 4 495 313 which is incorporated by reference herein the preferred methods for forming the desired lens when a diluent is used include centrifugal casting and cast molding for example using molds described in u s pat no 4 565 348 as well as combinations of these methods with the other methods described generally herein after the lens is prepared the dye which is dispersed throughout the lens must be bonded or fixed to the hydrophilic polymer composition which forms the lens this can be done using the conventional technique of contacting the lens with an aqueous base prior to hydration as disclosed for example in u s pat no 4 891 046 the preferred base is an alkali or alkaline earth metal carbonate or phosphate and the required contact time will depend on the contact temperature and the components of the hydrophilic polymer composition advantageously 0 25 weight percent or less of a surfactant with a hydrophilic lipophilic balance greater than 10 is added to the aqueous base to enhance the uniformity of the dye dispersion throughout the lens and to improve overall process efficiency the preferred surfactant for this purpose is glucam u2122 mle 80 ethoxylated glucose sold commercially by amerchol when bonding of the dye to the hydrophilic polymer backbone of the lens is sufficiently complete the lens can.