Röggla V, Langenbucher A, Leydolt C, et al. - Researchers conducted the study for providing clinical guidance on the use of intraocular lens (IOL) power calculation formulas according to the biometric parameters. Six hundred eleven eyes that underwent cataract surgery have been retrospectively analysed in subgroups according to the axial length (AL) and corneal power (K). The predicted residual refractive error was measured and compared to assess the accuracy of the following formulas: Haigis, Hoffer Q, Holladay 1 and SRK/T. In addition, the percentages of eyes with ≤±0.25, ≤±0.5 and 1 dioptres (D) of the prediction error have been recorded. The Haigis formula displayed the highest percentage of cases with ≤ 0.5 D in eyes with a short AL and steep K (90%), average AL and steep cornea (73.2%) but also in long eyes with a flat and average K (65% and 72.7%, respectively). Overall, in most subgroups, the Haigis formula shows correct results. Attention must, however, be paid to the axial eye length and corneal power when selecting the appropriate formula for the measurement of IOL power, particularly in eyes with unusual biometry.