Fig. 4

Achieved correction vs. Attempted correction with Nomogram 4. The achieved meridional power change correlated with the attempted change (p < 0.0001) and the nomogram correction differs significantly from the preoperative refraction (p < 0.0001). The nomogram proposes a − 5% reduction in planned meridional power with a − 0.39 D bias. A refraction of − 2.50 D sphere with − 1.50 D astigmatism at 63 degrees should be planned as − 2.79 D sphere with − 1.44 D astigmatism at 63 degrees