Recent developments in the intraocular lens formulae: An update

Background The precision of refractive outcomes after uneventful cataract surgery largely depends on the biometry and intraocular lens (IOL) formula used for selecting the IOL. To improve the accuracy of post-op refractive outcomes, several new IOL power calculation formulae have come up. This review would aim to summarise the differences among the new formulae in their performance among normal and variable ocular biometry conditions like short and long axial lengths.Methods A literature review was performed by searching the PubMed and Cochrane databases from 2016 to 2021, identified 483 articles, of which 51 were included in the review.Results We identified 15 new IOL formulas (including updates on older formulas) of which, only 8 newer formulas (BUII, Hill-RBF 2.0, Kane, Pearl DGS, LSF AI, Naesar 2, EVO 2.0 and VRF) met the eligibility criteria. They were compared according to the reported median absolute error, mean absolute error and percentage of eyes within 0.5D.Conclusion The Kane formula and Barrett Universal-II formula performed better than other formulas over the entire axial length (AL) spectrum. In the long eye (AL > 26.0 mm) sub-group, the Kane formula was the most accurate, while in the short eye (AL < 22.0 mm) sub-group, both Kane and EVO 2.0 formulas fared better than other formulas.