Complaints, irrespective of source, touching upon the professional conduct or conduct evincing unfitness for the practice of optometry made against optometrists licensed in this state, that may be received by or that may come to the attention of any member of the board, shall be referred by the president of the board to an impartial member of the board for preliminary investigation and further action as may be appropriate. The complaint must be in writing and signed by the person making the complaint or charge and shall contain the street address of the complaining party and each witness.