A Method to Evaluate the Frequency Dependence of Retinal Vascular and Neural Metrics to Stimulus Modulation.

PURPOSE

Flickering light stimulation induces functional hyperemia, characterized by vasodilation, blood flow augmentation, and venous oxygen elevation. We present a new method to investigate the frequency dependence of metrics associated with functional hyperemia.

METHODS

A novel optical imaging system was developed to quantify retinal blood vessel diameter (D), oxygen saturation (SO2), and the inner retinal oxygen extraction fraction (OEF) before and after light flicker at different frequencies. Measurements were performed in 10 visually normal subjects (20-62 years) at flicker frequencies from 2 to 30 Hz. In addition, a measure of neural function was obtained by steady-state pattern electroretinography (ssPERG) across a similar range of frequencies.

RESULTS

Flicker stimulation greater than 2 Hz increased D, increased SO2 in veins, and decreased OEF. The maximum response for all metrics was obtained between 16 and 30 Hz, indicating that vascular and oxygenation metrics share a similar frequency response with light flicker. ssPERG amplitudes were positively correlated with flicker-induced increases in venous D and SO2. ssPERG amplitude was negatively correlated with flicker-induced decreases in OEF.

CONCLUSIONS

We present a novel retinal imaging method to evaluate the frequency dependence of changes in D, SO2, and OEF to light flicker stimulation. The relationship between these metrics and ssPERG amplitudes was evaluated.

TRANSLATIONAL RELEVANCE

The frequency-dependent response of retinal D, SO2, and OEF established in healthy individuals herein has the potential to serve as a biomarker of vascular and tissue abnormality in future studies of retinal disease.