Intraocular lens power calculation for eyes with an axial length greater than 26.0 mm: Comparison of formulas and methods

PURPOSE: To evaluate and compare the accuracy of formulas and methods for calculating the intraocular lens (IOL) power for eyes with an axial length (AL) greater than 26.0 mm. SETTING: Ein-Tal Eye Center, Tel-Aviv, Israel. DESIGN: Retrospective case series. METHODS: The postoperative refraction results in myopic eyes with an AL over 26.0 mm were compared with the predicted refractions calculated using standard formulas (Holladay 1, SRK/T, Hoffer Q, and Haigis) with optical IOL constants, User Group for Laser Interference Biometry constants, and an AL-adjustment method and using new-generation formulas (Barrett Universal II, Holladay 2, and Olsen). RESULTS: In 76 (71.7%) of 106 eyes, the IOL was 6.0 diopters (D) or more (Group A) and in 30 eyes (28.3%) was less than 6.0 D (Group B). In Group A, the SRK/T, Hoffer Q, Haigis, Barrett Universal II, Holladay 2, and Olsen methods met the benchmark criteria of having a prediction error of +/- 0.5 D in at least 71.0% of eyes and +/- 1.0 D in 93.0% of eyes. In Group B, only the Barrett Universal II formula and the Holladay 1 and Haigis formulas using the AL-adjusted method met those criteria. CONCLUSION: When selecting IOLs for high and extreme myopia, choosing appropriate formulas and methods can yield accurate refractive results that meet benchmark criteria.