Intraocular lens power calculations in short eyes using 7 formulas.

Purpose: To investigate the accuracy of 7 intraocular lens (IOL) calculation formulas in predicting refractive outcome in eyes with axial lengths (AL) equal to or less than 22.0 mm and to evaluate factors contributing to prediction errors.

Setting: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, and private practice, Mesa, Arizona, USA.

Design: Retrospective case series.

Methods: Eighty-six eyes of 67 patients were included. Seven IOL calculation formulas were evaluated: Barrett Universal II, Haigis, Hill-RBF, Hoffer Q, Holladay 1, Holladay 2, and Olsen. The refractive prediction error was calculated as the difference between the postoperative refraction and the refraction predicted by each formula. The mean refractive prediction error and median absolute error were also calculated.

Results: The Hoffer Q and Holladay 2 formulas produced myopic refractive prediction errors of -0.22 diopter (D) and -0.23 D, respectively, and the Olsen formula produced a hyperopic refractive prediction error of +0.27 D (all P < .05). Without adjustment of the mean refractive prediction errors to zero, the only difference between formulas was that Hill-RBF had a statistically significantly smaller median absolute error than Hoffer Q (P < .05). With adjustment of the mean refractive prediction errors to zero, there were no statistically significant differences in the median absolute errors between the 7 formulas (P = .076).

Conclusions: The Hoffer Q and Holladay 2 formulas produced slightly myopic refractive prediction errors, and the Olsen formula produced hyperopic refractive prediction errors. When the mean numerical refractive prediction error was adjusted to zero, no statistically significant differences in the median absolute error were found between the 7 formulas.