Optical coherence tomography angiography (OCT-A) in an animal model for laser-induced choroidal neovascularization

Abstract

Purpose : Optical coherence tomography angiography (OCT-A) allows for noninvasive three-dimensional visualization of the retinal and choroidal vasculature without fluorescent dye injection. We compared OCT-A with conventional fluorescein angiography (FA) and confocal microscopy in the animal model of laser-induced choroidal neovascularization (CNV).

Methods : Rats underwent laser photocoagulation to induce CNV. In-vivo imaging was performed before and directly after as well as at day 2, 7, 14 and 21 following the laser treatment. OCT-A was compared to FA and confocal imaged flatmounts. Analysis included measurements of CNV area, vessel density and pixel intensity within/without the laser lesions.

Results : OCT-A allowed for high-resolution imaging of the retinal and choroidal blood vessels. Within laser lesions, signs of CNV formation occurred at day 7 with progression in size and number of small vessels until day 21. New blood vessels were visible by OCT-A especially in the deep vascular plexus, in the avascular zone (outer nuclear layer and ellipsoid zone) and the choroid but not by FA. Due to leakage and staining effects, CNV area appeared larger in FA compared to OCT-A images (p≤0.0001 for all tested layers, Fig. 1). Overall, CNV area in flatmounts was similar to OCT-A results and smaller compared to area of dye leakage by FA.

Conclusions : Detailed and high-contrast images of the retinal and choroidal vasculature can be accurately visualized without invasive dye injection by OCT-A imaging in-vivo. OCT-A imaging may allow for a more precise, spatial analysis of new blood vessel formation in CNV animal models as compared with conventional FA.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Fig.1: Analysis of the area of CNV for the superficial vascular plexus (SVP), intermediate vascular plexus (IVP), deep vascular plexus (DVP), outer nuclear layer (ONL), the ellipsoid zone (EZ), inner choroidal (IC) and outer choroidal (OC) layer imaged by OCT-A and FA following the laser treatment over time (D = day following laser treatment). The asterisks are indicating a significant difference (p≤0.0001) in CNV area calculated by the Mann-Whitney-U-Test, n.s. showing non significance results.