Reproducibility of retrobulbar blood flow velocity measurements in normal subjects using two different CDI devices

Purpose: This study was done to evaluate the intra- and inter-operator reproducibility of colour Doppler imaging (CDI) in assessing blood flow velocity in the ophthalmic (OA), central retinal (CRA) and short posterior ciliary arteries (SPCA) in healthy subjects. Materials and methods: The right eye of two groups of eight healthy volunteers was examined. Two radiologists and two ophthalmologists, divided into pairs, measured peak systolic velocity (PSV), end-diastolic velocity (EDV) and resistivity index (RI) of each vessel using a different CDI device for each group. The concordance between two measurements was evaluated with Lin’s concordance correlation coefficient (CCC). Results: Globally, very good degrees of intra-operator concordance were obtained for the PSV (0.859 cm/s), EDV (0.834 cm/s) and RI (0.859) of the OA. There was moderate concordance for PSV (0.574 cm/s) and EDV (0.594 cm/s) and good concordance for RI (0.694) for the CRA. Good degrees of concordance were obtained for the SPCA measurements. However, inter-operator concordance was found globally poor. Conclusions: These data show that CDI measurements in retrobulbar vessels are operator dependent. To increase the intra-operator and inter-operator concordance, rules should be adopted for timing of the examination and positioning of the probe to minimise the pressure applied on the eye.