Pursuant to section 74 of the Retirement and Social Security Law, the Comptroller has the exclusive authority to determine whether a member is permanently incapacitated for the performance of gainful employment. With respect to disability retirement applications filed pursuant to section 605 of the Retirement and Social Security Law, a member shall be considered permanently incapacitated for the performance of gainful employment if he is incapable of performing the duties normally, ordinarily and reasonably expected of his position.