Quantification of total retinal blood flow via dual-beam bidirectional Doppler optical coherence tomography for the assessment of neurovascular coupling in the human retina

Abstract

Purpose : To assess the absolute and relative increase in total retinal blood flow (TRBF) induced by neurovascular coupling (NC) in the human retina in-vivo.

Methods : For the presented data, six healthy volunteers were measured (two female, four male) with an average age of 30.3 ± 4.3 years. For each subject, TRBF was measured at baseline condition and during flicker stimulation. NC was induced by means of diffuse luminance flicker stimulation that operates at 12.5 Hz frequency. This allowed for the calculation of TRBF at both, baseline condition and while NC is active. Blood flow velocities were measured via dual-beam bidirectional Doppler Fourier-domain optical coherence tomography (FD-OCT). The vessel diameters for the flow calculation were assessed from FD-OCT phase B-scans. Central retinal arterial equivalents (CRAE) and central retinal venous equivalents (CRVE) very calculated in order to evaluate correlations between central retinal equivalents and TRBF at both, baseline and flicker stimulation state.

Results : The mean baseline TRBF was 36.4 ± 5.9 µl/min and the mean TRBF while flicker stimulation of the retina was 53.4 ± 7.6 µl/min. The measured increase in TRBF caused by flicker stimulation varied between 34 % and 66 %. The average increase obtained over all measured subjects was 47.6 ± 11.5 %. The mean increase of CRAE was 8.0 ± 3.2 % and mean increase in CRVE was 9.8 ± 3.3 % while flicker stimulation. The obtained values of TRBF showed a good correlation with CRAE values for baseline (r = 0.57) and flicker (r = 0.54) measurements. Likewise TRBF and CRVE values showed a good correlation for the baseline values (r = 0.54) but a weak correlation for the values measured while flicker stimulation (r = 0.14).

Conclusions : Dual-beam bidirectional FD-OCT allows to quantify NC in the human retina in vivo and may be a promising method for monitoring alterations in NC caused by various pathologies.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.