Accuracy of ocular axial length measurement with MRI

Background: This study assessed axial length measurements taken with MRI compared to A-scan ultrasonography for use in silicone-filled eyes with cataracts. Methods: This study was a double-blinded prospective comparison study of axial length measurements made by MRI and A-scan ultrasonography. MRI scans of 20 patients undergoing MRI were reviewed to determine axial length. Standard A-scan measurements of axial length were also obtained. Axial length measurements by MRI were compared to A-scan ultrasonography measurements. Results: In 36 eyes, an MRI scan was obtained in the correct plane to measure the axial length. The axial length measured by MRI was on average 0.18 ± 0.29 mm longer (range -0.41 to +0.7 mm) than the axial length measured by A-scan, for a refractive error average of +0.28 ± 0.58 D (SD), and a range of -1.06 to +1.52 D. Conclusions: Axial length measurements with MRI match reliably with axial lengths measured by A-scan ultrasonography.