Optimized intraocular lens power calculation in refractive lens exchange
1Servicio de Oftalmología, Hospital General Universitario Doctor Balmis, Spain.
Abstract:
This review aims to evaluate the factors affecting the accuracy of intraocular lens (IOL) power calculation and the strategies to optimize refractive predictability in eyes with atypical anatomy, prior refractive surgery, or phakic intraocular lenses. A narrative review of studies was conducted using PubMed, Scopus, and Web of Science up to March 2026, following PRISMA methodology. Articles were independently screened and reviewed by two authors. Studies on IOL calculation in normal and non-standard eyes, post-corneal refractive surgery, phakic IOLs, and refractive lens exchange were included. In axial myopia, new-generation formulas or third-generation formulas with Wang-Koch adjustment can compensate for the historical tendency toward hyperopic errors in these eyes. In short eyes, new-generation formulas outperform third-generation formulas, particularly in cases with shallow anterior chambers. The use of toric IOL calculators that adjust implant toricity at the corneal plane based on the effective lens position and account for posterior corneal astigmatism appears to improve outcomes. In eyes with high or non-vertical posterior corneal astigmatism, it may be beneficial to use IOL calculation methods that consider the effect of implant position. After myopic refractive surgery, the ASCRS calculator average or post-refractive versions of modern formulas may be valid options. In patients with phakic IOLs, it is recommended to ensure correct crystalline lens identification or to use formulas that do not rely on anterior chamber depth if measurement errors are significant. In conclusion, refractive predictability depends on ocular anatomy, prior surgery, and IOL characteristics. New-generation formulas generally outperform third-generation formulas in non-standard eyes, although the optimal choice varies by cohort. Selecting an appropriate calculation formula and carefully verifying biometric data are essential to improving refractive accuracy in refractive lens exchange.
