Imaging laser-induced choroidal neovascularization in the rodent retina using optical coherence tomography angiography

Abstract

Purpose : Utilizing small animal models of retinal diseases is important for understanding pathophysiology and drug development because of the constraints in using the human retina. In this study, we developed a rodent retinal optical coherence tomography angiography (OCTA) system to visualize laser-induced choroidal neovascularization (CNV) in the rodent retina.

Methods : High-speed OCTA prototype using a custom 1040 nm wavelength-swept laser operating at the 230 kHz A-scan rate was used to acquire a volumetric data of 1024x1024x3 A-scans over 1.7mm x 1.7mm and 3.5mm x 3.5mm areas in mice and rats, respectively. Amplitude decorrelation between consecutive B-scans from each vertical position was calculated to perform angiography. To evaluate the ability of OCTA in visualizing laser-induced CNV in the mouse and rat retina, ICGA, FA, and flat-mount images as well as OCTA were acquired 7 days after laser photocoagulation. Vasculatures of the inner retina, outer retina, and choroid were separately visualized after RPE flattening and layer segmentation. To demonstrate the feasibility of longitudinal studies using OCTA, OCT imaging was performed 6, 14, and 21 days after laser photocoagulation with and without anti-VEGF treatment. VEGF-Trap and DPBS were intravitreally injected 7 days after laser injury.

Results : Figs. 1(A-C) show OCT angiograms of the inner retina, outer retina, and choroid, respectively. OCTA of the outer retina shows laser-induced CNV vessels and shadows from the thick inner retinal vessels. Figs. 1(D-F) show ICGA, FA, and flat mount images of the same retina for comparison. Fig. 2 shows a relative decrease in CNV area and volume over time in the eyes treated with VEGF-Trap compared to those treated with DPBS. CNV area and volume were measured with OCTA.

Conclusions : OCTA enables longitudinal imaging in animal models of retinal diseases and promises to be an important imaging modality that offers more efficient and quantitative analysis for drug development.

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

 

OCTA, ICGA, FA and flat mount images of laser-induced CNV in the mouse retina. (A) Inner retinal blood flow. (B) Outer retinal blood flow showing CNV. (C) Choroid blood flow. (D) ICGA. (E) FA. (F) Flat mount. Scale bar: 200um.

 

Relative area (n=7) and volume (n=7) of laser-induced CNV measured with OCTA in the mouse retina. Outer retina blood flow of CNV (A) without anti-VEGF treatment and (B) with anti-VEGF treatment.