Comparison of The IOL Master(R) and A-scan Ultrasound: Refractive Results of 96 Consecutive Cases

ABSTRACT

PURPOSE: To study the refractive outcome of cataract surgery employing partial coherence interferometry (PCI) and to compare this outcome with that of A-scan ultrasound in a prospective study of 96 eyes of 96 patients that underwent phacoemulsification with intraocular lens (IOL) implantation. METHODS: The SRK-T formula was employed, using PCI (IOL Master(R) the only commercially available model) and A-scan ultrasound data, to predict patients' implanted IOL power. Four to six weeks after cataract surgery, the refractive outcome was determined, and results from the two different biometry methods were compared. RESULTS: Ninety-six patients (mean age 67.64, SD 9.91) underwent phacoemulsification with IOL implantation. The optical axial length obtained using the IOL Master(R) was significantly longer (p<0.001, Student's t-test) than the axial length obtained via by A-scan ultrasound, 24.29 (SD 1.80) mm vs. 24.19 (1.75) mm. When using the IOL Master(R), the mean prediction error (PE; planned target of refraction - postoperative refraction) was 0.30 (0.60) D, and the mean absolute prediction error (APE) was 0.51 (0.44) D. When using A-scan ultrasound, the mean PE was 0.01 (0.64) D, and the mean APE was 0.47 (0.43) D. The difference in mean APE between the two biometry methods was not statistically significant (p=0.236, Wilcoxon signed rank test). Among the eyes with an axial length greater than 25 mm, as determined by A-scan ultrasound, the difference in the mean APE was not statistically significant (0.48 (0.87) vs. 0.58 (0.61), p=0.094). Likewise, among the eyes for which with axial length measured by A-scan ultrasound longer than IOL Master(R), the difference in the mean APE error was not statistically significant, (0.33 (0.30) vs. 0.46 (0.41), p=0.110). CONCLUSIONS: IOL power calculation using the PCI is as accurate as that using A-scan ultrasound for predicting the postoperative refractive state of patients who have undergone cataract surgery.