Measurement of the anterior chamber depth and ocular axial length: transpalpebral B-mode ultrasound using an 18-MHz linear probe compared with the IOL Master 500

To determine the reliability of transpalpebral ultrasound in B-mode (B-TUS) with a high-resolution linear probe (18 MHz) in estimating both the ocular anterior chamber depth (ACD) and axial length (AL), as well as its agreement with the IOL Master 500 optical biometer.

Cross-sectional study on 82 eyes of 41 volunteers with no history of eye disease. ACD and AL were determined using B-TUS and the IOL Master 500. The agreement between the two tech-niques and the variability of B-TUS (inter- and intra-observer) were analyzed with the Bland-Altman method. To this end, the mean difference between measures±1.96 SD was calculated to determine the limits of agreement (LoA).

The mean difference±1.96SD between B-TUS and the IOL Master 500 was -0.41±0.25mm for ACD (p<0.001) and -0.48±0.45 mm for AL (p<0.001). The maximum variability for B-TUS (average±1.96SD) was 0.00±0.35 mm at the inter-observer level for AL, and 0.00±0.18mm at the intra-observer level for AL.

The determination of ACD and AL by B-TUS has a good re-liability and variability, in line with other sonographic techniques. However, it systematically provides smaller measurements than those obtained with the IOL Master 500, similar to the conventional ultrasound techniques. B-TUS could be useful in the assessment and follow-up of a wide range of ophthalmic diseases, in which a high accuracy in ACD and AL is not determinant.