Comparison of formulas and methods for high myopia patients requiring intraocular lens powers less than six diopters

To determine the best method to minimize postoperative hyperopia and achieve mild myopia in patients requiring low-powered (<6.00 D) MN60MA intraocular lenses (IOLs).

This retrospective non-comparative case series consists of 32 eyes (20 patients). Postoperative spherical equivalent (SE) refractions were compared using four methods: standard formulas with varying target refractions (Haigis -1.00 D, Hoffer Q -1.75 D, Holladay 1 -1.50 D and SRK/T -1.00 and -1.25 D), axial length adjustment methods for standard formulas targeted for both plano and -0.50 D, Barrett Universal II formula and the Haigis formula using separate constants for plus and minus IOLs (Haigis +/-). SE (mean, standard deviation, median, range), median absolute error (MedAE), prediction errors, percentage SE less than 0.25 D and greater than -1.00 D, percentage SE within ±0.50 and ±1.00 D of the targeted refraction were calculated.

All methods and formulas gave acceptable mean SE refractions ranging from -0.04 to -0.68 D. The Barrett Universal II, Haigis +/-, standard Haigis formula targeted for -1.00 D and the Holladay 1 formula targeted for -1.50 D met stricter criteria of final SE between 0.25 and -1.00 D in 94-100% of eyes and MedAE between 0.37 and 0.51 D. Other methods had more myopic or hyperopic outliers.

For these eyes with high myopia, the Barrett Universal II, Haigis +/-, standard Haigis targeted for -1.00 D and the standard Holladay 1 targeted for -1.50 D formulas produce the best results exceeding established benchmark criteria and minimizing hyperopic surprises.