Cal. Bus. & Prof. Code § 2556

It is unlawful to do any of the following: to advertise the furnishing of, or to furnish, the services of a refractionist, an optometrist, or a physician and surgeon; to directly or indirectly employ or maintain on or near the premises used for optical dispensing, a refractionist, an optometrist, a physician and surgeon, or a practitioner of any other profession for the purpose of any examination or treatment of the eyes; or to duplicate or change lenses without a prescription or order from a person duly licensed to issue the same.