In lieu of the retirement allowance for his or her life alone, a member or retired member may elect, or revoke or change a previous election prior to the approval of the previous election, to have the actuarial equivalent of his or her retirement allowance as of the date of retirement applied to a lesser retirement allowance, in accordance with one of the optional settlements specified in this article. The election or revocation or change thereof, with respect to a member subject to Section 21624 at retirement, shall apply to all of the retirement allowance, if, at
the effective date of retirement, the member has no spouse, children or dependent parents who would qualify for an allowance under Section 21624 after the death of the member; or, if at retirement there are persons who would so qualify, then the election, or revocation, or change thereof, with respect to any optional settlement other than optional settlement one, shall apply only to the portion of the allowance that exceeds the amount of the allowance payable to the survivor.
An actuarial equivalent under this article may be adjusted by the board for the intervals and upon the effective dates determined by the board.