((a)) ** .—** Notwithstanding any provision of chapter 1407 of this title and except for officers referred to in sections 14503, 14504, 14505, and 14506 of this title and under regulations prescribed by the Secretary of Defense—
((1)) the Secretary of the Army may, with the officer’s consent, retain in an active status any reserve officer assigned to the Medical Corps, the Dental Corps, the Veterinary Corps, the Medical Services Corps (if the officer has been designated as allied health officer or biomedical sciences officer in that Corps), the Optometry Section of the Medical Services Corps, the Chaplains, the Army Nurse Corps, or the Army Medical Specialists Corps;
((2)) the Secretary of the Navy may, with the officer’s consent, retain in an active status any reserve officer appointed in the Medical Corps, Dental Corps, Nurse Corps, or Chaplain Corps or appointed in the Medical Services Corps and designated to perform as a veterinarian, optometrist, podiatrist, allied health officer, or biomedical sciences officer; and
((3)) the Secretary of the Air Force may, with the officer’s consent, retain in an active status any reserve officer who is designated as a medical officer, dental officer, Air Force nurse, Medical Service Corps officer, biomedical sciences officer, or chaplain.
((b)) ** .—**
((1)) Subject to paragraph (2), an officer may not be retained in active status under this section later than the date on which the officer becomes 68 years of age.
((2)) The Secretary concerned may, with the consent of the officer, retain in an active status an officer in a medical specialty described in subsection (a) beyond the date described in paragraph (1) of this subsection if the Secretary concerned determines that such retention is necessary to the military department concerned. Each such retention shall be made on a case-by-case basis and for such period as the Secretary concerned determines appropriate.