Neurovascular coupling response: A follow-up study

Aims/Purpose: This work aims to assess the consistency of the neurovascular coupling (NVC) response of a healthy subject group at two visits 5 months apart.

Methods: Fundus images (4x4 degrees) of the macular region (3 baseline acquisitions and 3 acquisitions each preceded by flicker stimulation) of 13 healthy adults (one eye each, age (m+/-sd): 33.08+/-11.4 yrs.) were acquired with the rtx1 AO camera (ImagineEyes, Orsay, France). The rtx1 was configured for a 20 second, 15Hz, and 4 μW.cm^(-2) flicker stimulation over a 29x20 degrees area of the imaged eye fundus. Acquisitions for each subject were repeated 159+/-17 (m+/-sd) days later.

The lumen of retinal arterioles within the macular region was determined using custom-developed software for the automatic segmentation of lumen-wall interfaces. An experienced technician visually assessed all segmentations to reject subpar results. Lumen diameters were calculated from the distance between the lumen-wall interfaces as measured perpendicular to the vessel axis along a vessel segment. NVC responses were calculated per eye as the relative difference (%) of the lumen diameter after stimulation to the respective baseline.

Results: A total of 22 out of 156 images (14%) were rejected and excluded from further analysis. NVC responses ranged from 0.21% to 8.28% (3.36+/-2.75 % (m+/-sd)) for the first visit and from -0.24% to 9.13% (3.03+/-2.54 %) for the follow-up. Response differences between time points ranged from -6.15% (8.28% to 2.13%) to 4.21% (0.98% to 5.19%), with an average (sd) of 0.34(3.03) % for the group. A paired sample Wilcoxon test between time points is not statistically significant (p = 0.650), supporting that the responses are consistent between time points.

Conclusions: The obtained results show a consistent NVC response for a 5-month interval.