Integrated photoacoustic microscopy and optical coherence tomography image-guided laser induced branch retinal vein occlusion in living rabbits

Abstract

Spectral domain optical coherence tomography (SD-OCT) and photoacoustic microscopy (PAM) were integrated to improve the visualization of retinal vein occlusion (RVO) and retinal neovascularization (RNV). RVO and RNV were observed in living, New Zealand rabbits by Rose Bengal laser-induced retinal vein thrombosis. Multimodal imaging techniques including PAM, OCT, fluorescein angiography (FA), and color fundus photographs were utilized to observe and analyze changes in the retinal vasculature. Spectral domain OCT identified RNV cross-sectional structures, and progressive changes in retinal anatomy due to angiogenesis from the photothermal treatment were monitored at 4, 28, 35, 49, and 90 days post-laser. Compared to alternative methods, PAM in vivo high-contrast imaging possesses the capabilities to accurately visualize the treatment margins of occluded vasculature and areas of RNV. Results were obtained using a laser energy of 80 nJ, which is half a dose below the American National Standards Institute safety limit. The PAM system also demonstrated an increased depth of penetration, which provided high resolution images of the choroid and retinal vasculature when the optical absorption of hemoglobin was used to improve the visualize blood flow. Current modalities of imaging possess the ability to visualize RNV and RVO in two-dimensional and three-dimensional angiography. However, the system integrating both PAM and OCT can better visualize the depth and position of microvessels as well as surrounding structures. This specific multimodal ocular imaging technique may therefore be an improved technology to document minute changes in rabbit eye retinal vasculature while proving to be both safe and efficient.