Comparison of A-scan and MRI for the measurement of axial length in silicone oil-filled eyes

Aims: The aim of the study was to compare the accuracy of A-scan biometry and MRI for the measurement of axial length in silicone oil-filled eyes. Methods: This was a prospective randomised study of 70 patients. Biometry was performed using MRI in 33 patients (MRI group) and A-scan echography in 37 patients (A-scan group). The difference between predicted and final refraction was measured and evaluated statistically. Results: In patients with axial length >= 26 mm, the mean deviation of the final from predicted refraction was -1.23 (SD 0.67) D in the MRI group and -2.3 (SD 2.02) D in the A-scan group. The difference between these two groups was statistically significant (p = 0.02). In patients with axial length,26 mm, the mean deviation of the final from predicted refraction was -0.12 (SD 1.29) D in the MRI group and -0.33 (SD 1.39) D in the A-scan group. There was no statistical significance between the two groups (p = 0.629). Conclusion: For highly myopic patients MRI biometry was a more accurate measurement of axial length in silicone oil-filled eyes. A-scan and MRI biometry were comparably accurate in measuring axial length in patients with axial length <26 mm.