PURPOSE: To obtain the title lightweight resin suitable as optical material, molding material, film, coating compound, especially lens for reforming spectacles, comprising a (co)polymer of a specific (co)monomer.

CONSTITUTION: The aimed resin comprising a homopolymer of a monomer (e.g.-2,2'-spiro-5-vinyl-1,3-1',3'-benzoxyol or 2,2'-spiro-5-viuyl-4'methoxy-1,3-1',3,- benzoxyol) shown by the formula [R1 is -CH=CH2, -CH2-CH=CH2, -COOC (CH3)=CH2, -COOOH2-CH=CH2, -OCOO-CH2-CH=CH2, OCOOCH2-C(CH3)=CH2' -OCOCH=CH2 or -OCOC(CH3)=CH2; R2 is H, OCH3, -SCH3, CH3, C2H5 or -CH=CH2; A is 0 or S] or a copolymer comprising the monomer and a copolymerizable comonomer.