Correlation of Visually Evoked Functional and Blood Flow Changes in the Rat Retina Measured With a Combined OCT plus ERG System

PURPOSE. To correlate visually evoked functional and blood flow changes in the rat retina measured simultaneously with a combined optical coherence tomography and electroretinography system (OCT+ERG). METHODS. Male Brown Norway (n = 6) rats were dark adapted and anesthetized with ketamine/xylazine. Visually evoked changes in the retinal blood flow (RBF) and functional response were measured simultaneously with an OCT+ERG system with 3-mu m axial resolution in retinal tissue and 47-kHz image acquisition rate. Both single flash (10 and 200 ms) and flicker (10 Hz, 20% duty cycle, 1 -and 2-second duration) stimuli were projected onto the retina with a custom visual stimulator, integrated into the OCT imaging probe. Total axial RBF was calculated from circular Doppler OCT scans by integrating over the arterial and venal flow. RESULTS. Temporary increase in the RBF was observed with the 10 and 200-ms continuous stimuli (similar to 1% and similar to 4% maximum RBF change, respectively) and the 10-Hz flicker stimuli (similar to 8% for 1-second duration and similar to 10% for 2-second duration). Doubling the flicker stimulus duration resulted in similar to 25% increase in the RBF peak magnitude with no significant change in the peak latency. Single flash (200 ms) and flicker (10 Hz, 1 second) stimuli of the same illumination intensity and photon flux resulted in similar to 2 x larger peak RBF magnitude and similar to 25% larger RBF peak latency for the flicker stimulus. CONCLUSIONS. Short, single flash and flicker stimuli evoked measureable RBF changes with larger RBF magnitude and peak latency observed for the flicker stimuli.