Observation of choroidal circulation using index of erythrocytic velocity

Abstract

Objective: To describe a noninvasive method to visualize choroidal circulation by means of erythrocytic velocity.

Methods: Laser speckle flowgraphy (LSFG) and indocyanine green (ICG) angiography were performed on 9 volunteers. The LSFG measures the quantitative relative velocity index of erythrocytes (normalized blur [NB] value) in retinal and choroidal vessels. We averaged NB values from 3 pulsations and made composite 1.5-mm-square NB maps during 1 pulsation. By overlapping 5 adjacent maps, we created a panoramic 3.0-mm-square NB map of the posterior pole. The vascular patterns of the panoramic map and ICG angiography were compared. To determine the influence of retinal vessels, we induced branch retinal artery occlusion in 2 monkey eyes and compared the panoramic maps before and after occlusion.

Results: The NB map showed pulsatile blood flow in choroidal and retinal vessels. Vascular pattern contrast was improved in the NB map. Choroidal vessels in ICG angiography corresponded to those in the NB map. Vascular patterns in the map changed little before and after branch retinal artery occlusion.

Conclusions: The LSFG noninvasively visualized the hemodynamics of choroidal circulation, and the vascular pattern, which is mainly choroidal in origin, was comparable with that of ICG angiography.

Clinical relevance: The LSFG may be used to evaluate choroidal hemodynamics in various choroidal diseases.