Abstract
Purpose :
To identify the origin of the axial retinal vessel reflex seen on fundus photographs and its variation in health and disease.
Methods :
Color and infrared fundus photography, OCT, fluorescein angiography in 20 healthy subjects and 20 patients with systemic or local disease and perturbation were examined. Assessment was by visual inspection and grading, validation by review of experimental data from a published study,
Results :
The axial reflex was found to increase in intensity with the definition of the patterns of flow on OCT and to be minimal or absent in non-perfused vessels. In eyes with low arterial pressure and poor perfusion, the axial reflex arteries was weak or absent, as was normal intravascular OCT profile of flowing blood. The reflex from the vessel wall was an order of magnitude smaller than that from the flowing blood (Fig. 1).
Conclusions :
The axial retinal vessel reflex is predominantly produced by flowing blood, in agreement with erythrocytes being oriented with their flat side facing the vessel wall, flow rates increasing from the vessel wall toward its axis. Hence, the axial reflex will disappear when the movement of blood is arrested. The observations suggest that the enhanced axial reflexes seen in patients with arterial hypertension are caused by vessel narrowing leading to faster flow, to sustain volumetric flow, with increasing velocity gradients (shear rates) leading to an increasingly ordered concentric layering and reflectivity of the erythrocytes.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.