Abstract
Purpose :
MA perfusion status may influence diabetic retinopathy onset and progression or worsening of macular edema. However, structural characteristics of individual MAs have not previously been clearly associated with perfusion attributes. This study utilizes MA structural information to estimate perfusion parameters through advanced computational analysis of high resolution (2.5μm) AOSLO images.
Methods :
MAs were imaged using AOSLO multiply scattered light imaging with 75-frame videos. MA boundaries were manually segmented, and 3-D models were constructed assuming rotational symmetry with respect to the centerline. Mean, maximum and minimum blood flow velocities previously measured in the parafoveal vasculature were used as boundary conditions at the MA inlets. Computational fluid dynamics modeling estimated shear rate (SR), wall shear stress (WSS) and perfusion velocity (Vel) within each MA. Low SR is associated with blood cell aggregation and clotting. Abnormal WSS levels have been linked to endothelial cell dysfunction.
Results :
Ten MAs were imaged from 7 eyes of 7 diabetic subjects. 5 were saccular (4 partially clotted) and 5 fusiform (all fully perfused). The mean±SD SR, WSS, and Vel were: 13.6±28.0S-1, 0.11±0.17Pa, and 44.6±64.7μm/s, respectively. Lower SR (11.4±30.1 vs 15.7±25.5S-1), WSS (0.09±0.19 vs 0.12±0.14Pa), and Vel (33.0±63.8 vs 56.1±63.4μm/s) were observed in MAs that were saccular as compared to fusiform. All three variables were lowest at areas adjacent to outpouchings of the MA wall furthest away from the inlet and outlet. In the 4 partially perfused saccular MAs, intraluminal clot was present in areas estimated to have the lowest SR (3.6±15.9S-1 in clotted areas vs. 14.9±32.5S-1 in perfused areas), as well as WSS and Vel.
Conclusions :
This technique enables noninvasive, in vivo estimation of perfusion parameters within MAs in the diabetic eye. In this small group, WSS was found to be lowest in the MA regions furthest away from the feeding vessels. Our results indicate that areas of low SR are associated with clot location in saccular MAs. Future studies will evaluate the association between these flow-based variables and MA progression, leakage and local neural retinal pathology.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.