(a) At the request of the insurance carrier, the commissioner may order that impairment income benefits and supplemental income benefits be reduced in a proportion equal to the proportion of a documented impairment that resulted from earlier compensable injuries.
(b) The commissioner shall consider the cumulative impact of the compensable injuries on the employee's overall impairment in determining a reduction under this section.
(c) If the combination of the compensable injuries results in an injury compensable under Section 408.161, the benefits for that injury shall be paid as provided by Section 408.162.