D.C. Mun. Regs. tit. 17, § 6415
6415.1 An optometrist licensed under the Act shall include the designation 'O.D.'; 'Optometrist'; or 'Doctor of Optometry' following his or her name in any advertisement, or written display of his or her name in the District of Columbia.
SOURCE: Final Rulemaking published at 55 DCR 12043 (November 21, 2008).