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

Abstract

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 (OCTþERG).METHODS. Male Brown Norway (n ¼ 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 OCTþERG system with 3-lm 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 (~1% and~4% maximum RBF change, respectively) and the 10-Hz flicker stimuli (~8% for 1-second duration and~10% for 2-second duration). Doubling the flicker stimulus duration resulted in~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~23 larger peak RBF magnitude and~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.

Functional optical coherence tomography of neurovascular coupling interactions in the retina

“…By providing excellent sectioning capability, optical coherence tomography (OCT) provides a noninvasive method to differentiate individual retinal layers . Functional OCT imaging has been explored to achieve depth‐resolved IOS imaging of the retina . However, it is still challenging to achieve selective mapping of neural‐IOS and hemodynamic‐IOS changes.…”

Dense concentric circle scanning protocol for measuring pulsatile retinal blood flow in rats with Doppler optical coherence tomography

“…A research-grade, spectral domain OCT system, designed and built by our group for various imaging studies in the animal retina [15][16][17] was modified for use in this study. Briefly, a broad bandwidth superluminescent diode (λ c ¼ 1060 nm, Δλ ¼ 110 nm, Superlum Ltd., Ireland) was used to achieve 3. , was designed to deliver a collimated imaging beam of 1.5 mm diameter to the rat cornea, thus achieving ∼5-μm lateral resolution in retinal tissue.…”

The Effect of Acutely Elevated Intraocular Pressure on the Functional and Blood Flow Responses of the Rat Retina to Flicker Stimulation

“…The OCTþERG system was developed by our research group for various animal retinal studies [36][37][38] and was recently used to evaluate the effect of single-flash and flicker stimuli on the total axial RBF. 34 In this study, a different scanning protocol was used in order to evaluate the total retinal blood flow (TRBF) before, during, and after IOP elevation. Briefly, the OCT system operates in the 1060-nm spectral region and provides~3-lm axial and~5-lm lateral resolution in the rat retina, at 92-kHz image acquisition rate.…”

“…[29][30][31][32][33] Recently, our research group has developed a combined OCTþERG system that allows for examination of the neurovascular coupling in the rat retina. 34 A study conducted with this system in healthy rats under normal IOP showed that flicker-induced changes in the RBF are time-correlated with amplitude and latency changes of the ERG traces.…”