Influence of Ocular Biometric Parameters on IOL Power Calculation Accuracy in Short and Normal Axial Length Eyes.

INTRODUCTION

The aim of this study was to assess the effect of including lens thickness (LT) in modern intraocular lens (IOL) formulas and evaluate the influence of ocular biometric parameters on IOL power calculation accuracy in short and normal axial length (AL) eyes.

METHODS

This retrospective cohort study included 174 eyes (74 short AL < 22 mm, 100 normal AL 22-24 mm). Preoperative biometry was obtained using IOLMaster 700. Predicted refractions were calculated using SRK/T, Haigis, Barrett Universal II (BUII), Kane, and Emmetropia Verifying Optical (EVO) formulas, with and without LT. Spearman correlation and multivariate regression analyses were performed to identify biometric predictors of refractive error.

RESULTS

Short eyes had significantly shallower anterior chamber depth (ACD), smaller white-to-white (WTW), thicker LT, and higher mean keratometry (Km) and corneal astigmatism (CA) (all p < 0.01). No significant differences in mean absolute error (MAE) were detected between most formula pairs after adjustment in either subgroup. LT inclusion resulted in a less myopic mean prediction error in both subgroups (all p < 0.01), but MAE improvements were only seen in normal eyes (p < 0.05). AL and WTW were consistent predictors of absolute prediction error (APE) overall, with shorter AL and smaller WTW associated with greater APE. In short eyes, AL showed the strongest association with APE, whereas in normal eyes, WTW was most strongly correlated with APE.

CONCLUSIONS

Short eyes exhibited greater biometric variability. Incorporation of LT improved the overall prediction accuracy of modern IOL formulas, particularly in normal AL eyes. AL and WTW were the most influential biometric factors affecting refractive prediction outcomes.

TRIAL REGISTRATION: Chinese Clinical Trial Registry (ChiCTR), ChiCTR2600116749; retrospectively registered on 14 January 2026.