Wash. Rev. Code § 18.53.160
All agencies of the state and its subdivisions, and all commissions, clinics and boards administering relief, public assistance, public welfare assistance, social security, health insurance, or health service under the laws of this state, shall accept the services of licensed optometrists for any service covered by their licenses relating to any person receiving benefits from said agencies or subdivisions and shall pay for such services in the same way as practitioners of other professions may be paid for similar services. None of the said governmental agencies, or agents, officials or employees thereof, including the public schools, in the performance of their duties shall in any way show discrimination among licensed ocular practitioners.
RCW 18.53.160