Secondary IOL power calculation. A comparison of an optical and a biometric method.

In 40 aphakic eyes undergoing secondary IOL implantation, the axial length was calculated optically as well as measured by ultrasound, and the two methods of axial length determination were compared to evaluate the accuracy in the calculation of secondary IOL power. The mean refractive prediction error (+/- SD) was 0.18 diopters (+/- 0.96) and -0.37 diopters (+/- 0.83) using the optical and the biometric method, respectively. The difference in mean value was significant, whereas the variation around the mean value was not found to be significantly different between the two methods. A calculated axial length may offer a valuable alternative to biometry in the aphakic eye, increasing the accuracy of secondary IOL power calculation.