Doppler ultrasonographic estimation of ocular resistive and pulsatility indices in normal unsedated cows

Introduction - Resistive index (RI) and pulsatility index (PI) are indirect measurements of blood flow resistance that may be used to evaluate the vascular pattern in ophthalmology. The application of ultrasonography on ocular structures of cattle are limited at the biometric evaluation of the bovine eye. To our knowledge, no reports are available describing values for ocular RI and PI indices in unsedated cows. Aim - The main purpose was to report normal values for RI and PI of internal ophthalmic artery (IOA) and long posterior ciliary arteries (LPCAs) in unsedated clinically healthy cows, performing the Doppler ultrasonographic examination. Materials and methods - Twenty Brown Swiss dried healthy cows were subjected to a complete ophthalmic examination. IOA and LPCAs were scanned using Colour Doppler Imaging (CDI) in order to calculate RI and PI. Transpalpebral ultrasonographic images from both eyes were obtained using a 7.5 MHz duplex sectorial transducer. For each vessel the mean value and the standard deviation of RI and PI were expressed. The t-student test was applied to evaluate differences between right eye and left eye. P< 0.05 was considered significant. Results and discussion - The mean RI (± SD) was 0.57±0.07 and 0.58±0.09 for IOA of right and left eye respectively; 0.54±0.11 and 0.53±0.08 for LPCAs of right and left eye. The mean PI (±SD) was 0.95±0.07 and 0.93±0.09 for IOA of right and left eye; 0.80±0.11 and 0.84±0.08 for LPCAs of right and left eye. No significant differences in RI and PI values between left and right eye were reported. Conclusion - The CDI of ocular vessels and the measurement of blood flow parameters are feasible in cow and it may be used to evaluate vascular changes of certain ocular disorders affecting food animals.