Prospective comparison of accuracy of intraocular lens calculation formulas in phacovitrectomy: a pilot study in a real-world clinical practice

Purpose To compare the accuracy of intraocular lens (IOL) power calculations among IOL formulas after phacovitrectomy. Methods We prospectively enrolled 206 eyes of 206 patients who underwent 25-gauge phacovitrectomy, without gas tamponade, for macular pathology. Pre-operative optical biometry used the IOLMaster 700 to calculate the IOL power with the new formulas, i.e. the Barrett Universal II (BU II), Emmetropia Verifying Optical version 2.0, Hill-Radial Basis Function (RBF) version 3.0, Kane, and Ladas Super Formula, and conventional formulas, i.e. Haigis, Hoffer Q, Holladay 1, Holladay 2, and Sanders-Retzlaff-KrafffT (SRKfT). A single-piece foldable IOL was implanted in all cases. Manifest refractions were measured before and 3 months after surgery. Results The BU II formula showed the lowest standard deviation and mean and median absolute errors and had the highest percentage of eyes with a refractive prediction error within +/- 0.25 D. The absolute error was significantly lower with the four new formulas, except the Hill-RBF, than with the Hoffer Q (all p= 0.010) and Holladay 1 formulas (all p= <= 0.010). The absolute error with the BU II formula was also lower than that with the Holladay 2 (p =0.012) and SRK/T (p =0.024) formulas. Conclusion Overall, the new IOL formulas, except the Hill-RBF, were superior to some of the conventional formulas for calculating IOL power in phacovitrectomy.