Visual stimulus-evoked transient blood flow and blood vessel diameter changes in the healthy human retina measured with a combined OCT+ERG system

Neurodegenerative retinal diseases, such as glaucoma, age-related macular degeneration and diabetic retinopathy, cause gradual damage to the retinal morphology, blood vasculature, and neuronal function, and ultimately lead to blindness. In this study, a retinal OCT system was combined with a clinical electroretinography (ERG) system to investigate visually-evoked transient changes in the retinal blood flow (RBF) and blood vessel diameter (BVD) in the healthy human retina. The OCT system offered 2.7 <i>µ</i>m axial resolution in retinal tissue and 98 dB sensitivity for 1.1 mW imaging power and 250 kHz image acquisition rate. Doppler OCT (double circular scans around the optic nerve head) and ERG traces were acquired from healthy subjects in response to 10 Hz, white light flicker stimuli and different stimulus intensities. The ERG system was used to generate visual stimuli of precise timing, duration, luminance, and flicker frequency, as well as to confirm the retinal neuronal response to the visual stimulation. MATLAB-based custom algorithms were developed to track time-dependent changes in the RBF and BVD from the OCT images. Results from this study revealed a rapid transient increase in the RBF accompanied by transient vasoconstriction and vasodilation of the retinal blood vessels in response to the flicker stimulation. The amplitude and latency of the RBF and BVD responses were dependent on the stimulus intensity as well as the blood vessel type (arteries or veins).