Effect of pupillary dilation on ocular biometry and intraocular lens power calculation: prospective cohort study

PURPOSE: To investigate the effect of pupillary dilation on ocular biometry and intraocular lens (IOL) power calculation with actual postoperative outcomes. SETTING: Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China. DESIGN: Prospective cohort study. METHODS: This study included 84 patients with cataract undergoing phacoemulsification. Axial length (AL), keratometry, anterior chamber depth (ACD), central corneal thickness (CCT), lens thickness (LT), and white-to-white (WTW) before and after pupillary dilation were measured using IOLMaster 700. The prediction errors (PEs) and absolute prediction errors (AEs) before and after dilation were compared, calculated by Barrett Universal II, Emmetropia Verifying Optical (EVO) 2.0, Hoffer QST, Kane, LISA, and Pearl-DGS formulas. Multiple and stepwise linear regression analyses were conducted to identify the factors associated with the shift of PE. RESULTS: Pupillary dilation induced significant biometric changes, including increased ACD (0.091 mm) and decreased LT (-0.036 mm), along with changes in AL, CCT, and WTW. A small but statistically significant myopic shift in mean PE was observed with postdilation compared with predilation, with the mean shifts for 5 of the 6 formulas (all except Hoffer QST) ranging from -0.045 diopters (D) (EVO 2.0; SD = 0.147; 95% CI -0.077 to -0.013) to -0.034 D (Kane; SD = 0.146; 95% CI -0.066 to -0.002). However, mean and median AE remained unchanged (P > .05). Regression analysis revealed that changes in AL, keratometry, and ACD were significant predictors of the myopic shift across all formulas. CONCLUSIONS: Pupillary dilation may induce a mild myopic shift in IOL power calculations compared with undilated state. However, this shift does not seem to significantly affect the overall predictive accuracy of modern IOL formulas. Further research in larger cohorts is warranted to confirm these findings.