Updating the No-History Method in Intraocular Lens Power Calculation After Myopic Laser Vision Correction

PURPOSE: To describe the Shammas-Cooke formula, an updated no-history (NH) formula for IOL calculation in eyes with prior myopic laser vision correction (M-LVC), and to compare the results to the Shammas PL, Haigis-L and Barrett True-K NH formulas. SETTING: Bascom Palmer Eye Institute (BPEI), The Lennar Foundation Medical Center, University of Miami, Miami, Florida, USA; Dean A. McGee Eye Institute (DMEI), University of Oklahoma, Oklahoma City, Oklahoma, USA; and private practice, Lynwood, California, USA and St Joseph, Michigan, USA. DESIGN: Retrospective observational study. METHODS: We analyzed two large series of cataractous eyes with prior M-LVC. The training set (BPEI series of 330 eyes) was used to derive the new corneal power conversion equation to be used in the novel Shammas-Cooke formula, and the testing set (165 eyes of 165 patients in the DMEI series) to compare the updated formula to three other M-LVC NH formulas on the ASCRS calculator: Shammas PL, Haigis-L and Barrett True-K NH. RESULTS: Mean prediction error was 0.09±0.56, -0.44±0.61, -0.47±0.59 and -0.18±0.56 D, and the mean absolute error was 0.43, 0.60, 0.61 and 0.45 D for the Shammas-Cooke, Shammas PL, Haigis-L and Barrett True-K NH. The percentage of eyes within ± 0.50 D was 66.7% versus 47.9%, 48.5% and 65.5%, respectively. CONCLUSION: The Shammas-Cooke formula performed better than the Shammas PL and Haigis-L (P<0.001 for both) and as well as the Barrett True-K NH formula (P=0.923).