Evolution of Biometric Formulas and Intraocular Lens Selection in Challenging Cases

Abstract

Various novel intraocular lens (IOL) power calculation formulas have been described to increase refractive precision following cataract surgery. These include the Barrett Universal II, Emmetropia Verifying Optical (EVO), Kane, Naeser 2, Olsen, Panacea, Pearl DGS, Radial Basis Function (RBF), T2, and VRF formulas. With a few notable exceptions, historical and regression formulas—first- and second-generation IOL formulas like Sanders, Retzlaff, Kraff (SRK), Binkhorst, Hoffer, and SRKII—are generally regarded as outdated. The effective lens position (ELP) is accounted for in third- and fourth-generation formulas which include more biometric data. A possible alternative that has shown to be remarkably accurate when used with the Olsen method is ray tracing. Artificial intelligence-derived IOL formulas are becoming increasingly common and may yield better lens power prediction accuracy. Despite improvements in surgical technique, biometry measurements, and IOL calculations, some clinical circumstances continue to challenge cataract surgeons to determine the appropriate IOL power. These unique situations include pediatric eyes, post-refractive eyes, and corneal ectasias. The obstacles to reliability include unrepeatable measurements and inaccurate biometry examinations. Researchers have tried to identify the most accurate IOL estimations for these challenging clinical scenarios to overcome these obstacles.