Effect of anterior chamber depth on predictive accuracy of seven intraocular lens formulas in eyes with axial length less than 22 mm.

PURPOSE: This study aimed to evaluate whether different anterior chamber depth (ACD) affects the predictive accuracy of intraocular lens formulas in eyes with axial length (AL) less than 22 mm. METHODS: Eighty-five eyes of 85 patients with AL less than 22 mm were included in this retrospective study, which were divided into three groups: Group 1, ACD less than 2.4 mm; Group 2, ACD between 2.4 and 2.9 mm; and Group 3, ACD greater than 2.9 mm. Optical biometry with partial coherence interferometry was performed in all cases. The median absolute error (MedAE) was compared by Friedman's test, using the optimized lens constant, among seven formulas (Barrett Universal II, Haigis, Hill-RBF, Hoffer Q, Holladay 1, Holladay 2, and SRK/T) in each group. RESULTS: Friedman's test showed no significant difference in MedAE among all formulas in Groups 1 and 3. However, as the Haigis formula had the highest MedAE and lowest percentage of eyes within ±0.25 Diopter, it is least preferred in Group 1. On the contrary, in Group 3 it fared the best, having the least MedAE and highest percentage of eyes within ±0.25 Diopter. In Group 2, Friedman's test gave significant difference, and post-hoc analysis showed statistical superiority of Haigis over the Holladay 1 (p=0.02), Holladay 2 (p=0.01), Hill-RBF (p=0.04), and SRK/T (p=0.02) formulas. However, there was no statistical difference between the Barrett Universal II, Haigis, and Hoffer Q formulas. CONCLUSION: Considering the ACD in eyes with AL less than 22 mm, Haigis is the preferred formula while SRK/T proved to be the worst formula in Groups 2 and 3.

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.