If an employee receives a permanent injury such as specified in section 10 of this chapter after having sustained another permanent injury in the same employment, he shall be entitled to compensation for both injuries, but the total compensation shall be paid by extending the period and not by increasing the amount of weekly compensation, and when such previous and subsequent permanent injuries in combination result in total permanent disability or permanent total impairment, compensation shall be payable for such permanent total disability or permanent total impairment, but payments made for the previous injury shall be deducted from the total payment of compensation due.
IC 22-3-3-15