Abstract
Multi-wavelength en face photoacoustic microscopy (PAM) was integrated with a spectral domain optical coherence tomography (SD-OCT) to evaluate optical properties of retinal vein occlusion (RVO) and retinal neovascularization (RNV) in living rabbits. The multi-wavelength PAM of the RVO and RNV were performed at several wavelengths ranging from 510 to 600 nm. Rose Bengal-induced RVO and RNV were performed and evaluated on eight rabbits using color fundus photography, fluorescein angiography, OCT, and spectroscopic en face PAM. In vivo experiment demonstrates that the spectral variation of photoacoustic response was achieved. The location and the treatment margins of the occluded vasculature as well as the morphology of individual RNV were obtained with high contrast at a laser energy of 80 nJ, which was only half of the American National Standards Institute safety limit. In addition, dynamic changes in the retinal morphology and retinal neovascularization were administered using PA spectroscopy at numerous time points: 0, 3, 7, 14, 21, 28, and 35 days after photocoagulation. The proposed multi-wavelength spectroscopic PAM imaging may provide a potential imaging platform to differentiate occluded retinal vasculature and to improve characterization of microvasculature in a safe and efficient manner.
Highlights
Retinal vein occlusion (RVO) represents a major cause of vision loss in elderly patients, affecting more than 16 million people worldwide [1,2,3]
Blue arrow indicates the location of major retinal veins, black arrow exhibits the location of the major retinal artery, whereas white and yellow arrows depict the position of the optics nerve and choroidal vessels, respectively
As shown in Fig. 2(a4), various layers of retinal tissues were observed such as the ganglion cell layer (GCL), RPE, choroidal vessels, and sclera
Summary
Retinal vein occlusion (RVO) represents a major cause of vision loss in elderly patients, affecting more than 16 million people worldwide [1,2,3]. FA and ICGA visualize only the superficial capillaries, but no quantitative depth information of the vasculature can be obtained [5]. Both ICGA and FA are invasive, requiring the injection of an intravenous exogenous dye, and can cause nausea and vomiting in up to 10% of patients and rarely anaphylaxis which can cause death [8]. OCT is a non-invasive technique to detect and visualize the retinal anatomy and layers with high resolution. OCT provides limited information on the choriocapillaris and choroidal vasculature and blood flow [9]. OCTA provides high resolution images of both the superficial and deep capillary plexus [10]. OCTA cannot demonstrate leakage, provides limited visualization of microaneurysms, can often have motion artifacts, and has limited ability to visualize the choroid and choriocapillaris microvasculature [10,12]
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