A method for calculating the required power of a toric implant by using both the measured pre-operative corneal astigmatism and the predicted surgically-induced post-operative astigmatism. The surgically-induced post-operative astigmatism is predicted using power vector analysis of the surgical technique employed by the surgeon. Such a method provides a more accurate method of calculating the required post-operative refractive power of the implant. The method can be implemented manually, but preferably is automated by implementation on a computer through appropriate software.