Each state employee who elects, under the provisions of sections 5-158a to 5-158f, inclusive, to contribute to both Social Security and full part A of the state employees retirement system and who has, in effect, an option providing for his spouse, under the State Employees Retirement Act, shall be allowed, upon written application to the Retirement Commission, prior to January 1, 1970, to cancel or reduce or retain such option and such option, if cancelled, shall be of no force or effect or shall have such effect as the reduced option provides. Upon the retirement of a member who has cancelled or reduced such option under the provisions of this section, his retirement salary shall be reduced by such amount or amounts, if any, as the Retirement Commission shall determine as the actuarial equivalent of the value of the protection for the amount of the retirement salary which would have been payable to the spouse if the member had died between (1) the first date on which the spouse would have been entitled to a retirement salary if the member had died on such date and (2) the date of cancellation, or to the value of the excess of such protection over that under the reduced option, as the case may be.