Okla. Stat. tit. 59, § 646.4

Unless a health-related reason for the limitation is noted in the patient's medical records, contact lens prescriptions shall not have an expiration date of less than twelve (12) months from the date the prescription is authorized or the last date of the contact lens evaluation by an Oklahoma-licensed optometrist, whichever date is later. In no event shall a contact lens prescription be valid twelve (12) months after the date of authorization by an Oklahoma- licensed optometrist.