The accuracy of different generation intraocular lens power formulas in eyes with axial length less than 22 millimeter

Aim: In this study, we aimed to investigate the accurate formulas for eyes with axial length (AL) less than 22 millimeters among usually used six intraocular lens (IOL) calculation formulas. Material and Methods: This retrospective study included 137 eyes with short ALs below 22 mm of 122 patients who underwent phacoemulsification surgery with the same type of IOL implantation. The biometric values of the patients were obtained using optical low coherence reflectometry (OLCR) for six formulas involving Hoffer Q, SRK-T, Haigis, Barett Universal II, Holladay 2 and Hill-RBE All patients in the postoperative period had the best-corrected visual acuity level equal to or higher than 20/40. While comparing the accuracy of these six IOL calculation formulas, the mean absolute error (MAE), and the median absolute error (MedAE) values were taken into account. Results: The MAE values for Hoffer Q, SRK-T, Haigis, Holladay 2, Hill-RBF and Barrett Universal II formulas were 0.390, 0.390, 0.324, 0.327, 0.331 and 0.208, respectively. Also the rank of MedAE values for the mentioned formulas was 0.245, 0.310, 0.310, 0.250, 0.255 and 0.190. The lowest MAE and MedAE values were found in the Barrett Universal II formula, whereas the highest one was in the SRK/T formula with a statistical significance (p<0.001). After Bonferroni correction, there was no statistically significant difference between the Barrett Universal II formula and the other formulas except for SRIVT (p>0.01). Three patients (2.5%) were in the +/- 0.75 D range, 15 patients (12.3%) were in the +/- 0.50 D. and the remaining 104 (85.2%) patients were during the +/- 0.25 D at the first-month follow-up. Discussion: Although Barrett Universal II appears to be the most accurate IOL calculation formula, third, fourth and other newer generation formulas have also good predictive value for accurate estimation of IOL power in short eyes.