The following persons, firms and corporations are exempt from the operation of the provisions of this chapter except the provisions of section 336.200:
(1) Physicians or surgeons of any school lawfully entitled to practice in this state;
(2) Persons, firms and corporations, not engaged in the practice of optometry, who sell eyeglasses or spectacles in a store, shop or other permanently established place of business on prescription from persons authorized under the laws of this state to practice either optometry or medicine and surgery;
(3) Persons, firms and corporations who manufacture or deal in eyeglasses or spectacles in a store, shop or other permanently established place of business, and who neither practice nor attempt to practice optometry, and who do not use a trial case, trial frame, test card other than that used by the customer or customers alone, vending machine or other mechanical means to assist the customer in selecting glasses.