Agreement on Keratometry Readings and Computed IOL Power using Haigis and SRK/T formulas between Ray Tracing (iTrace®) and Partial Coherence Interferometry (IOLMaster®) among Patients in an Outpatient Surgical Center
Thonnie Rose O. See, MD, Richard L. Nepomuceno, MD
Objective: To determine if there is an agreement between keratometry readings and intraocular lens (IOL) power calculation using Haigis and Sanders, Retzlaff and Kraff theoretical (SRK/T) formulas obtained by iTrace® and IOLMaster®.
Methods: A retrospective chart review of patients who underwent preoperative biometry using both IOLMaster® and iTrace® from January 2015 to July 2015 and satisfied the inclusion/exclusion criteria were included in the study. The average keratometry, cylinder power and predicted IOL power were computed accordingly. Agreement between devices was analyzed using Bland Altman.
Results: A total of 70 eyes from 35 study participants were included in the analysis. The means of average keratometry values obtained from IOLMaster® and iTrace® were 43.9 ± 1.3 D and 43.6 ± 1.3 D respectively. The paired mean differences in the average keratometry and cylinder power between instruments were -0.3 ± 0.3 and 0.1 ± 0.4 respectively. There was a statistically significant difference in the proportion between the number of times there will be a need to change IOL power and the number of times IOL power will remain the same using the Haigis formula with a p value of <0.0005. Conclusions: Average keratometry values, cylinder power and IOL calculation using the Haigis formula obtained by the two devices tested did not show agreement. There is agreement using the SRK/T formula. Keywords: ray tracing, partial coherence interferometry, keratometry, IOL power, SRK/T, Haigis