Comparative Accuracy Analysis Of Seven New Intraocular Lens Power Calculation Formulas In Short Eyes (<22Mm) Undergoing Cataract Surgery.

To evaluate the performance of latest newly developed intraocular lens (IOL) calculation formulas on the prediction accuracy in short (<22mm) axial length (AL) eyes. 

Tertiary Hospital with day-case cataract surgery facilities. Retrospective case-series study of 107 short eyes (AL <22mm) that underwent phacoemulsification and IOL implantation with the same IOL platform (Tecnis®, Johnson & Johnson: models ZCB00, DIB00, ZCU and DIU). Preoperative eye biometry (IOLMaster700 (Zeiss) and Lenstar900 (Haag-Streit)) included AL, mean keratometry power, anterior chamber depth, lens thickness, central corneal thickness, and white-to-white distance.

Seven formulas were evaluated: Barrett Universal II (BUII), Cooke K6, Emmetropia Verifying Optical (EVO) 2.0, Hill-Radial Basis Function (HRBF) 3.0, Hoffer QST, Kane and Pearl-DGS. Prediction accuracy (diopters, D) was determined 1 month after surgery and reported by mean prediction error (PE) and its standard deviation, median absolute error (MedAE), mean absolute error (MAE) and percentage of eyes with PEs within +/-0.25 D to +/-1.50 categories (0.25 D increase). Multiple comparisons were analyzed under Bonferroni correction.  The statistical package STATA v.15.1 (StataCorp, College Station, Texas, USA) was used for the analysis and a p-value <0.05 was considered as statistically significant.

Pearl-DGS, EVO, HRBF and Kane formulas showed the best prediction accuracy by MedAE (respectively 0.21, 0.22, 0.22 and 0.23 D), with no statistically significant differences in MAE (p-value>0.05) among them. Cooke, BUII and HQST formulas showed a worse performance compared to the former formulas (p-value>0.05), reporting MedAE of 0.34, 0.28 and 0.28 D respectively. Regarding mean PE, Pearl-DGS, EVO and HRBF formulas accurately targeted emmetropia (respectively +0.06+/-0.40, -0.04+/-0.38 and +0.02+/-0.43 D) whereas Kane reported a slightly inaccurate myopia tendency (-0.16+/-0.40). Overall, the Pearl-DGS, EVO, HRBF and Kane formulas showed the higher proportion (respectively 84.1%, 84.1%, 84.1% and 83.2%) of patients within +/-0.50 D of PE.

In summary, all studied formulas performed well in <22mm AL eyes, reporting a proportion of PE +/-0.50 D of >=68%. However, Pearl-DGS, EVO, HRBF and Kane formulas showed the best prediction accuracy and should be recommended accordingly. By contrast, BUII, COOKE and HQST reported the worst accuracy and should not be used if alternative formulas are available. More studies with increased sample sizes and multivariate analysis are needed to fully elucidate the best formula in short eyes, especially to detect differential biomarkers to select the best formula for each patient.