Comparison of Biometric Measurements and Refractive Results between Applanation Ultrasonography and Three Different Interferometries

PURPOSE: To compare ocular biometry and refractive results measured using conventional applanation ultrasonography and 3 different optical interferometries, Lenstar LS900(R), AL-Scan(R) and OA-2000(R). METHODS: The biometries of 31 cataractous eyes were measured using ultrasonography, Lenstar LS900(R), AL-Scan(R) or OA-2000(R). The axial length, anterior chamber depth and keratometry were measured. The SRK/T formula was used to calculate intraocular lens power. Two months after cataract surgery, the refractive outcome was determined and results from the 4 different biometry methods were compared. RESULTS: Axial lengths were 23.39 +/- 0.95 mm, 23.42 +/- 0.98 mm, 23.43 +/- 0.98 mm and 23.44 +/- 0.98 mm measured using ultrasonography, Lenstar LS900(R), AL-Scan(R) and OA-2000(R), respectively with no statistically significant differences observed (p = 0.996). The anterior chamber depth and keratometry were 3.14 +/- 0.41 mm, 3.10 +/- 0.38 mm and 3.13 +/- 0.39 mm (p = 0.936) and 44.41 +/- 1.52 D, 44.54 +/- 1.57 D and 44.44 +/- 1.52 D (p = 0.937) for Lenstar LS900(R), AL-Scan(R) and OA-2000(R) respectively. There were no statistically significant differences between the 3 optical devices. The mean absolute error of the 4 different devices were not statistically significant (p = 0.722). CONCLUSIONS: The ocular biometric measurements and prediction of postoperative refraction using ultrasonography, Lenstar LS900(R), AL-Scan(R) or OA-2000(R) showed no significant differences.

Comparison of the Refractive Results Measured by Ultrasound and Partial Coherence Interferometers

PURPOSE: To compare ocular biometry measured by applanation ultrasonography and IOL Master(R), and evaluate the accuracies of the refractive outcome after cataract surgery. METHODS: The biometries of 76 cataractous eyes were measured using ultrasonography and IOL Master(R). The SRK-T formula was employed to predict the patient's implanted IOL power. Two months after cataract surgery, the refractive outcome was determined, and results from the 2 different biometry methods were compared. RESULTS: There were no statistically significant differences in axial length (AXL) and anterior chamber depth (ACD) between ultrasonography and IOL Master(R) (p = 0.501). When using ultrasonography, the mean absolute error (MAE) of the ultrasonography and IOL Master(R) was 0.53 +/- 0.30 diopter (D), 0.55 +/- 0.41 D, respectively. The difference between the 2 biometry methods was not statistically significant (p = 0.110). CONCLUSIONS: Although the difference was not statistically significant, AXL measured by IOL Master(R) was longer and ACD measured by IOL Master(R) was deeper than when measured by A-scan. This difference was more pronounced in patients with a short AXL. The accuracy of IOL power calculation was similar between the 2 devices.

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

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.