Influence of pupil dilation on predicted postoperative refraction and recommended iol to obtain target postoperative refraction calculated by using third-and fourth-generation calculation formulas

Abstract

Purpose: To evaluate the influence of pupil dilation on predicted postoperative refraction (PPR) and recommended intraocular lens (IOL) power to obtain target postoperative refraction calculated by using the third-and fourth-generation IOL power calculation formulas with a new optical biometer. Methods: This retrospective study included 162 eyes with cataract that underwent uneventful phacoemulsification with IOL implantation. PPR, recommended IOL power, anterior chamber depth (ACD), and lens thickness (LT) were measured pre-and post-pupil dilation. The change in PPR detected by using third-generation (Hoffer Q and SRK/T) and fourth-generation formulas (Haigis and Holladay 2) and the changes in ACD and LT were evaluated pre-and postdilation. The influence of dilation on the recommended IOL power calculated by each formula was analyzed. Result: ACD and LT significantly changed from pre-to postdilation. The mean absolute change in PPR between pre-and postdilation was significantly higher for fourth-generation formulas compared with third-generation formulas. The change in PPR between pre-and postdilation showed a significantly positive correlation with change in ACD and a significantly negative correlation with change in LT with fourth-generation formulas, but not with third-generation formulas. The discrepancy rate of recommended IOL power between pre-and postdilation calculated by fourth-generation formulas was significantly higher than that calculated by third-generation formulas. Conclusion: ACD and LT significantly changed by dilation. PPR and recommended IOL power significantly changed more by dilation when using fourth-generation formulas compared with third-generation formulas. Given the significant correlations of the change in PPR (between the pre-and postdilation) in the fourth-generation formulas and the changes in ACD and LT, the latter changes may be key in influencing dilation in the fourth-generation power calculation. Knowledge of the influence of dilation on fourth-generation formulas could help improve IOL calculation.