Foveal microvascular imaging: Optical coherence tomography angiography (OCTA) vs. adaptive optics scanning light ophthalmoscope fluorescein angiography (AOSLO FA)

Abstract

Purpose : OCTA is a promising clinical tool for noninvasive visualization of retinal microvasculature but it has not yet been validated with high resolution in vivo imaging. We used AOSLO FA in a side-by-side comparison with OCTA on healthy and diseased eyes to evaluate their similarities and differences.

Methods : 3 controls (3 eyes) and 6 patients (6 eyes) with diabetic retinopathy, branch retinal vein occlusion, or sickle cell retinopathy were imaged using a commercial OCTA system (Optovue Avanti RTVue-XR) and AOSLO FA (Pinhas et al., 2013). A 10x10° OCTA full vessel layer scan and a 6x6° AOSLO FA montage centered at the fovea were obtained for each eye (Fig. A&B) and skeletonized semi-automatically using custom software (Fig. C&D). Foveal avascular zone (FAZ) area, perimeter, and acircularity (FAZ perimeter divided by perimeter of circle with equal area) were measured. Vessel density at 3 annular regions of interest (ROI) defined by distance away from the FAZ margin (100, 200, & 300 µm) was computed as the total vessel length divided by ROI area. Paired t-tests were used to assess statistical significance. Images were compared for differences in vessel identification (Fig. C&D).

Results : OCTA and AOSLO FA demonstrated no statistically significant difference in FAZ perimeter, acircularity, and vessel density at all 3 ROIs. FAZ area showed a small but statistically significant difference (OCTA 0.38±0.27 vs. AOSLO FA 0.38±0.28 mm²; p=0.02). Certain vessel segments were seen on AOSLO FA but not on OCTA and vice versa (Fig. C-F). OCTA is prone to artifacts due to eye movement and lower lateral resolution compared to AOSLO FA but has short scan time and the ability to reveal multiple capillary layers in a single scan.

Conclusions : OCTA showed good comparability to AOSLO FA at the fovea in both healthy and diseased eyes with minor quantitative and qualitative differences. These results suggest that OCTA may serve as a good screening tool, but further evaluation in a larger group of eyes is needed.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

OCTA (top) and AOSLO FA images (bottom) of a control. A&B) Foveal perfusion maps. C&D) Skeletonized maps showing differences in vessel identification. E&F) Magnified regions (A&B yellow boxes); arrows indicate vessels visible only on OCTA. Scale bars: A-D 300µm; E&F 50µm.