Mitsui Chemicals, the Tokyo-based supplier of raw material for lenses, announced earlier this week that Costco Wholesale would start using its MR series of high refractive index lens monomers as a standard option for its eyeglasses sold in the U.S. The membership-based U.S. retailer had been offering mainly polycarbonate ophtalmic lenses to its clients until recently as is standard in the U.S. market, but after it started using it in October last year, the retailer decided to switch fully to Mitsui’s MR from this March. The Japanese company commented that this would spur its efforts to further transition its lens business from polycarbonate to the MR series. Produced from thiourethane resin, the MR series’ are already being used by most international lens manufacturers. According to Mitsui, the MR materials offer a unique combination of thinness, lightness, resistance and clarity.