Comparison of Axial Length and Postoperative Refraction between Applanation Ultrasonography and Low-coherence Reflectometry

Purpose: To compare axial length applanation ultrasonography (A-scan) (CineScan B-Scan; Quantel Medical, Bozeman, MT, USA) and low-coherence reflectometry (Lenstar LS900((R)); Haag-Streit, Bern, Switzerland), the accuracy of the predictive postoperative refraction of both instruments, and the intraocular lens (IOL) calculators. Methods: A total of 250 eyes of 191 patients who received cataract surgery were included in the study. The axial length was measured by the A-scan and Lenstar LS900((R)). The SRK-2, SRK/T, and Olsen formulas were used to calculate the IOL power, and the difference between the predictive and actual postoperative refractions after 6 weeks and the probability that they were within 0.25 diopters (D) and 0.5 D were compared. Results: The mean axial lengths measured by the A-scan and Lenstar LS900((R)) were 23.42 +/- 0.94 mm and 23.55 +/- 0.95 mm, respectively, which showed a statistically significant difference (paired t-test, p = 0.000). When comparing the difference between the predictive and actual postoperative refractions, the results of the A-scan using the SRK-2 and SRK/T formulas were significant toward the hyperopia, and the results of the Lenstar LS900((R)) using the SRK-2, SRK/T, and Olsen formulas were significant toward the myopia (paired t-test, p = 0.001 and p < 0.001, respectively). When comparing the mean absolute difference between the two refractions and the probability that they were within 0.25 D and 0.5 D, the Lenstar LS900((R)) using the Olsen formula significantly showed the highest accuracy (McNemar test, p = 0.045 and p = 0.002; p = 0.010 and p = 0.002, respectively). Conclusions: The A-scan using the SRK-2 and SRK/T formulas showed that the actual postoperative refraction was more hyperopic than the predicted refraction, whereas the Lenstar LS900((R)) resulted in more myopic findings. The accuracy of predictive postoperative refraction was highest with the Lenstar LS900((R)) using the Olsen formula.