Longitudinal monitoring of choroidal neovascularization by OCT angiography in mice

Abstract

 

Purpose

 

Early detection of choroidal neovascularization (CNV) remains challenging in clinical practice by existing optical coherence tomography (OCT) and fluorescein angiography. Recently developed OCT angiography enhanced the blood flow contrast and suppressed the other static tissue signals, which allows us to visualize CNV directly. We hypothesize that OCT angiography can effectively detect CNV.

 

Methods

 

Adult pigmented mice were anesthetized by ketamine/xylene cocktail and subjected to laser treatment following established protocols of laser induced CNV around optic disc. Two OCT systems working in near infrared (NIR-OCT) and visible light range were used to provide complementary images for CNV characterization. A peripapillary area of 2x2mm² centering optic nerve disk was imaged with both OCT systems. The OCT angiography scanning protocol scanned the same B-scan location twice and took the difference to enhance the blood flow contrast. The choroidal vasculature was extracted from the three-dimensional OCT angiography. OCT structural image and angiography were registered and compared between NIR and visible light OCT images. Four different CNV lesions were monitored longitudinally for 4 weeks after laser.

 

Results

 

NIR-OCT provides better penetration depth into choroidal layer (sample image can be found in Figure 1) and the visible light OCT provides superb axial resolution down to 1 micrometer. We quantified the CNV area/volume from 3D angiography. We observed the choroidal vascular remodeling on both NIR and visible light OCT, which started around 4 days and peeked one week after laser induction. The CNV lesion gradually regressed afterwards.

 

Conclusions

 

Compared to conventional OCT images, OCT angiography provides enhanced contrast from vasculature and can be used to detect and monitor the progression of CNV.  

 

Figure 1. NIR OCT angiography of a CNV mouse. (a) Sample OCT angiography B-scan. The dash box indicates the CNV location. (b) OCT angiography of major retinal vessels from the layer indicated by black arrow in (a). (c) OCT angiography of retinal capillaries from the layer indicated by purple arrow in (a). (d) OCT angiography of choroidal vessels from the layer indicated by red arrow in (a). CNV position is circled by the dash ring. Bar: 100 µm for (a) and 200 µm for (b).