Registered nurses, hired and compensated by the department of health on a per diem basis, shall not be members of the Retirement System or subject to the provisions of the Retirement System by reason of such employment.
Members of the Retirement System on the effective date of this section shall have the option to be exercised in writing on a form to be furnished by the retirement board and to be filed at the office of the Retirement System not later than March 31, 1988, to exclude compensation for per diem nursing as compensation for all Retirement System purposes.
The provisions of this section shall be prospective only, shall be effective January 1, 1988 and shall not give any person a claim for refund of pension contributions prior to January 1, 1988.