2M.D. Professor, Marmara University Faculty of Medicine, Department of Ophthalmology, İstanbul/TURKEY Purpose: To evaluate the precision of the biometric measurements for intraocular lens power calculations obtained by an optical low-coherence reflectometry (OLCR) biometer and an immersion ultrasound biometry (IUB).
Materials and Methods: In a prospective study, biometric measurements were taken with OLCR and IUB+automated keratometry in 126 eyes of 99 patients. SRK-II, SRK/T, Holladay, Hoffer Q, Haigis formulas were used to calculate the power of the implanted IOL. Measurements of axial length (AL), anterior chamber depth (ACD), keratometric readings (K), and the recommended lens power to achieve emmetropia obtained with OLCR were compared with those obtained with IUB. The results were evaluated using Bland-Altman analyses and Spearman correlation calculations.
Results: High correlations for AL, ACD, and K measurements were observed between the two devices (r=0.99, 0.87 and 0.87, respectively, p<0.0001). The axial length measured with OLCR was slightly longer than that measured with IUB (mean difference (MD) 0.06 mm, 95% LoA: 0.40, -0.28), ACD was shorter (MD -0.2 mm, 95% LoA: 0.32, -0.73), K readings were flatter (MD -0.6 D, 95% LoA: 0.8,-0.20). The recommended lens power to achieve emmetropia (OLCR-IUB) was higher for SRK- II (MD 0.2 D, 9%5 LoA -1.5,1.9), SRK/T (MD 0.7 D, 95% LoA -2.7,1.3), Holladay (MD 0.6 D, 95% LoA 2.1, -1.0) and Hoffer Q (MD 0.6 D, 95% LoA 2.4, -1.3), and was lower for Haigis (MD -0.6 D, 95% LoA 1.5, -2.8), (p<0.001).
Conclusion: Although there was high correlation between biometric measurements and IOL power calculations, the mean differences between the two biometry devices were significant.
Keywords : Cataract, IOL power calculation, optical biometry, ultrasound biometry