US Patent 11833771 Method for making photochromic contact lenses

Described herein is a method for producing a contact lens comprising a central photochromic zone that has a diameter of about 13 mm or less and is concentric with the central axis of the contact lens. The method comprises: applying, in the center of the molding surface of a male mold half, a drop (having a volume of about 5 μL or less) of a first polymerizable fluid composition containing at least one photochromic compound and a relatively-high molecular weight polysiloxane vinylic crosslinker for increasing the viscosity and adhesion on the molding surface of the male mold half; dosing a second polymerizable fluid composition in a female mold hald; closing the female mold hald with the male mold half with the drop thereon to form a molding assembly; and curing the second polymerizable fluid composition and the drop of the first polymerizable fluid composition in the molding assembly.