The provisions of section 20-138b shall apply to every individual or group hospital or medical expense insurance policy and every individual or group hospital or medical service plan contract delivered or issued for delivery or renewed in this state after October 1, 1975, which provides coverage or benefits for services or treatments which are within the definition of optometry as set forth in section 20-127. If any such policy or contract provides coverage or benefits for any such services or treatments when rendered by a person licensed under chapter 370, such policy or contract shall provide identical coverage or benefits for such services or treatments when rendered by a person licensed under this chapter, provided this section shall not alter or enlarge in any way the services or treatments which persons licensed under this chapter are authorized to perform.