OCT Angiography (OCTA) in Healthy Human Subjects

Abstract

 

Purpose

 

To evaluate the feasibility of noninvasive retinal angiography using a prototype using swept-source (SS) and spectral-domain (SD) optical coherence tomography (OCT) angiography.

 

Methods

 

Data was acquired using a Cirrus (Carl Zeiss Meditec, Dublin, CA) SS-OCT and SD-OCT prototype angiography systems. Five healthy subjects (nine eyes) with no past ophthalmologic history were recruited. 3x3mm regions centered on the fovea, nasal macula, and temporal macula were imaged. Retinal vasculature was assessed in three horizontal slabs consisting of the inner, middle, and outer retina. The vasculature was reconstructed using an intensity-based algorithm into separate en face images. Post-processed en face OCT angiograms were analyzed with ImageJ (NIH, Bethesda, MD) to quantify the density of retinal microvasculature using the “Auto Local Threshold” plug-in (Landini G. v1.5).

 

Results

 

OCTA in healthy subjects resembled fine capillary networks that have been demonstrated in previous histological studies of human cadaver eyes. Retinal vessels were not visualized in the outer retina. Within the central macula and temporal macula, the inner retina displayed continuous capillaries traveling in the same retinal plane while the middle retinal slab contained a lattice pattern of vessels. The nasal macular region showed capillary segments radiating out from the optic disc in the inner retina while the middle retinal slab featured a lattice pattern of discontinuous vessel segments. Vessel density analyses using ImageJ are shown in Figures 1 and 2.

 

Conclusions

 

Noninvasive, high-resolution angiograms produced by OCTA show qualitatively similar vascular patterns to previous histological images of the retina. OCTA angiography can reliably and reproducibly image the fine capillary networks of the retina and may have a role in assessing the retinal microvasculature when conventional fluorescein angiography cannot be performed.  

 

Fig. 1. Vessel density analysis of the central macular region of a healthy subject yielded an average total density of 31.68% ± 1.15% in the inner retina and a density of 30.86% ± 1.20% in the middle retina.

 

 

Fig. 2. Vessel density analysis of the nasal macular region of a healthy subject yielded an average total density of 31.59% ± 1.40% in the inner retina and a density of 31.47% ± 1.62% in the middle retina.