Sections 90, 390 and 447 of the Retirement and Social Security Law authorize eligible members of the New York State and Local Employees' Retirement System and the New York State and Local Police and Fire Retirement System to elect to receive a retirement allowance without optional modification or, alternatively, to elect to receive a modified retirement allowance under one of several statutory retirement options provided in those sections. Sections 90 and 390 also authorize the comptroller to approve other optional benefits which shall be the actuarial equivalent of the basic retirement allowance without optional modification. This part shall provide for the availability of four such retirement options to eligible Tier 1 members, and two such options to eligible Tier 2 members. The five-year and ten-year certain options provided in sections 345.2 and 345.3, of this Part, are already available to Tier 2 members pursuant to section 447 of the Retirement and Social Security Law.