15 U.S. Code § 7604 - Expiration of contact lens prescriptions
(a) In general
A contact lens prescription shall expire—
(1) on the date specified by the law of the State in which the prescription was written, if that date is one year or more after the issue date of the prescription;
(2) not less than one year after the issue date of the prescription if such State law specifies no date or a date that is less than one year after the issue date of the prescription; or
(b) Special rules for prescriptions of less than 1 year
If a prescription expires in less than 1 year, the reasons for the judgment referred to in subsection (a)(3) shall be documented in the patient’s medical record. In no circumstance shall the prescription expiration date be less than the period of time recommended by the prescriber for a reexamination of the patient that is medically necessary.