Accuracy of New Intraocular Lens Power Calculation Formulas: A Lens Thickness Study

Purpose To investigate whether using lens thickness measurement as an optional input improves the refractive accuracy of four new generation formulas. Methods Consecutive patients scheduled for cataract surgery were enrolled. Preoperative biometry was performed with an OA-2000 optical biometer (Tomey). All patients received the same monofocal intraocular lens (AcrySof SN-60WF; Alcon Laboratories, Inc). The Barrett Universal II (BUII), Emmetropia Verifying Optical (EVO), Kane, and Radial Basis Function (RBF) formulas were analyzed with and without the inclusion of lens thickness as an input. Postoperative refraction was measured at 1 month. The mean prediction error (PE), the median absolute error (MedAE), and the percentage of eyes with a PE within ±1.00 diopters (D) or less were calculated after constant optimization. Results The final analysis was performed on 169 eyes of 169 patients. Comparison of the mean PE, MedAE, and the percentage of eyes with a PE within ±0.25, ±0.50, ±0.75, and ±1.00 D resulting from each formula with and without lens thickness did not reveal any statistically significant difference. Cochran's Q test showed a statistically significant difference among formulas in the percentage of eyes with a PE of less than ±0.50 D (P = .042). However, Dunn's post-hoc test did not show any statistically significant difference between any pair of formulas. Conclusions Lens thickness measurement did not improve the accuracy of the BUII, EVO, Kane, or RBF formulas. The RBF formula yielded the same results with and without lens thickness, thus making this input useless. [J Refract Surg. 2021;37(3):202-206.].