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

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. 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. 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. 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. Chinese Clinical Trial Registry (ChiCTR), ChiCTR2600116749; retrospectively registered on 14 January 2026. When cataract surgery is performed, an artificial lens is implanted in the eye to restore clear vision. Choosing the correct lens power is especially challenging in eyes that are shorter than normal. This study examined whether including lens thickness, a measurement of how thick the natural lens is, improves the accuracy of modern lens power calculation formulas, and which eye measurements most strongly influence prediction errors. We reviewed data from 174 eyes, including eyes with short and normal eye length. Several commonly used calculation formulas were tested with and without including lens thickness. We also analyzed which eye measurements were most closely related to errors in vision prediction after surgery. We found that shorter eyes showed greater variation in eye structure. Including lens thickness reduced overall prediction error, particularly in eyes with normal length. Eye length and corneal diameter were the most important factors affecting accuracy. In short eyes, eye length had the greatest impact, while in normal eyes, corneal diameter played a larger role. These findings may help ophthalmologists better understand which measurements are most important when selecting artificial lenses and improve visual outcomes after cataract surgery.