Precision of intraocular lens power prediction in eyes shorter than 22 mm: An analysis of 6 formulas.

Purpose: To analyze the precision of 6 intraocular lens (IOL) power calculation formulas in predicting refractive outcome in eyes with an axial length (AL) less than 22.0 mm.

Setting: Department of Ophthalmology, All India Institute of Medical Sciences, Raipur, India.

Design: Retrospective observational study.

Methods: Patients with an AL less than 22.0 mm were included in the study. If both eyes were eligible, a randomly selected eye was chosen. Optical biometry with partial coherence interferometry (PCI) was performed in all cases. Six formulas were analyzed: Barrett Universal II, Haigis, Hoffer Q, Holladay 2, RBF Method and SRK/T. The mean numerical error was defined as the difference between the actual postoperative spherical equivalent (SE) at the 1-month follow-up and the predicted postoperative SE. The median absolute error was calculated and compared between all 6 formulas after the zeroing of the mean numerical error by adjusting the lens constant individually for each formula.

Results: The study comprised 50 eyes of 50 patients. The Friedman test was applied to compare the median absolute error between the 6 formulas after the zeroing of the mean numerical error. Post hoc analysis and Bonferroni correction for multiple comparisons showed no significant statistical difference between them.

Conclusion: The Barrett Universal II, Haigis, Hoffer Q, Holladay 2, RBF method and SRK/T formulas were equally accurate in predicting the IOL power in eyes shorter than 22.0 mm.