Comparative Analysis of Optical Biometry and Conventional Ultrasound A-Scan for Biometric Calculations of Eye

Title Comparative analysis of optical biometry and conventional ultrasound a-scan for biometric calculations of eye Aim To evaluate the predictability of refractive outcome using optical and ultrasound biometry in getting near emmetropia post operatively and to compare the axial length (AL), intraocular lens (IOL) power measured with Lenstar LS 900 with those obtained with ultrasound a-scan (Echorule2, Biomedix) in cataract patients. Material& methods After proper clearance from the ethical committee, the data of 231 eyes of 138 adult patients who had undergone surgery for visually significant cataract in one or both eyes at our centre was analyzed retrospectively for the study. Every eye had undergone two measurements each with an optical biometer (OS) (Lenstar, Haag Striet) and with ultrasound A-scan (UAS) (Echorule2, Biomedix). Optical biometry was performed first followed by ultrasound measurements. SRK-T formula was used for calculation of IOL power. Results The mean axial length of measured with OS was 23.46 1.50 mm (range, 20.62-31.87mm) and that measured with UAS was 23.37 1.52mm (range, 20.2-32.29mm). The axial lengths were compared using independent t-test, the p-value (0.526) was not found to be statistically significant and the mean difference was 0.089. The mean IOL measured with OS was 20.67 4.35D and that measured with UAS was 20.86 4.32D. The IOL powers were compared using independent t-test, the p-value (0.63) was not found to be statistically significant and the mean difference was -0.19. The BlandAltman plots showed good agreement between devices with less than 5 % of eyes that were outliers. In both the groups, majority of the patients had spherical equivalents within 1D. On comparison, the post-operative refraction was not statistically significant. Conclusion Optical biometry with OCLR technology to measure axial length is very precise and interchangeable with ultrasound measurement with no clinical difference in post-operative refraction in cataract patients.