(a) An employee is eligible to use time contributed to the sick leave pool of the agency if the employee has exhausted the employee's sick leave because of:
(1) a catastrophic illness or injury; or
(2) a previous donation of time to the pool.
(b) The board of trustees of the state employee group benefits program established under Chapter 1551, Insurance Code, shall:
(1) classify, for the purposes of this subchapter, those injuries and illnesses that are catastrophic; and
(2) provide a written statement of the classification to the governing body of each state agency.