PURPOSE: To compare blood flow velocity measurements obtained with two different linear probes (7.5 MHz and 12 MHz). MATERIALS AND METHODS: CDI measurements were performed in 31 eyes of 19 individuals with a 12 MHz and a 7.5 MHz probe. Measurements were taken in the ophthalmic artery (OA), central retinal artery (CRA), temporal short posterior ciliary arteries (TSPCA), and nasal short posterior ciliary arteries (NSPCA). With each probe, three measurements of each vessel were obtained, and end-diastolic velocity (EDV), peak systolic velocity (PSV), and resistance index (RI) were calculated. RESULTS: For EDV, the variation among replicates with the 7.5 MHz probe was between 13.99% and 19.51% and with the 12 MHz probe between 15.40% and 23.17%. For PSV, the variation among replicates was between 5.16% and 9.98% and between 6.58% and 10.71%, respectively with each probe. For RI, the variation among the replicates was between 3.10% and 8.97% and between 3.93% and 10.16%, respectively with each probe. The variation between probes was between 15.02% and 23.07% for EDV, between 10.72% and 13.24% for PSV, and between 4.27% and 6.05% for RI. The difference between estimated means was only significant for EDV in the TSPCA (P = 0.019), PSV in the TSPCA (P = 0.0002), as well as NSPCA (P = 0.003) and RI in the CRA (P <0.001) and NSPCA (P <0.044). CONCLUSION: The observed variation among three measurements is similar with both the 7.5 MHz and the 12 MHz probes. However, the 7.5 MHz probe tends to measure slightly higher values for some parameters.
