US Patent 11886045 Method for making photochromic contact lenses

Described herein is a method for producing photochromic contact lenses, in particular, photochromic silicone hydrogel contact lenses. The method comprises a step of cast molding of a lens-forming composition including an iniferter to form an unprocessed contact lens having iniferter moieties covalently incorporated into its polymer matrix and a step of iniferter-induced graft-polymerization of a photochromic vinylic monomer to the polymer matrix only in its central region which is circular and concentric with the central axis of the unprocessed contact lens. The obtained photochromic contact lens has a central pupillary region that only can undergo a reversible color change upon exposure to UV/HEVL-radiation.