A Novel Method to Measure Retinal Displacement Using Ultra-Widefield Fundus Autofluorescence Imaging

Abstract

Purpose : To introduce a novel method to measure retinal displacement in 3D using ultra-widefield fundus autofluorescence (UWF-FAF) imaging.

Methods : Images were acquired from patients presenting with primary macula-off RRD treated with pneumatic retinopexy (PnR) or pars plana vitrectomy (PPV). A coordinate grid was applied at the OD center of each UWF-FAF image. Two masked graders selected corresponding points on the retinal vasculature and retinal vessel printings (RVPs) within Zone 1, a circular region centered on the fovea with a radius extending to the center of the optic disk (Figure 1). 2D UWF-FAF images were projected to a 3D projection using OD and fovea coordinates. Vertical, horizontal, and diagonal arc distances between corresponding vessel and RVP pairs were calculated (Figure 2). Vector displacements of the RVP to vessel were calculated and averaged within Zone 1.

Results : 170 retinal vessel-RVP pairs were identified from 54 UWF-FAFs. Mean retinal displacement in Zone 1 was 0.36±0.38 mm with an absolute mean angle of displacement of 94.93±41.48° and directionality of displacement of 191.84±97.39°. Mean Zone 1 displacements were 0.44±0.42 mm and 0.21±0.27 mm in PPV (n=34) and PnR (n=19) eyes respectively, and was significantly greater in PPV eyes than PnR eyes (p=0.041). Between groups no significant difference in mean angle of displacement or directionality was found.

Conclusions : We present a novel method of quantitatively assessing displacement of retinal tissue that considers retinal curvature, via retinal vessels and RVPs on UWF-FAF.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Figure 1: Similarities in contour, bifurcation, and curvature of the vessel and retinal vessel printings were used to select coordinate pairs that represent the same location of the vessel and retinal vessel printing. A: Zone 1 of a UWF-FAF image with no markings. B: Zone 1 of the same UWF-FAF image with RVPs highlighted in white. C: Zone 1 of the same UWF-FAF image with selected vessel (red) and RVP (blue) coordinate.

 

Figure 2: Schematic showing the measurements taken between corresponding vessel and retinal vessel printing (RVP) points. V represents the coordinate of the vessel bifurcation which matches the RVP bifurcation, represented by R. Dashed lines indicate distance measurements taken. V-R represents the distance between the vessel and RVP coordinates as well as the vector of displacement. The angle of displacement is represented by angle α.