OCT angiography (OCTA) has recently garnered immense interest in clinical ophthalmology, permitting ocular vasculature to be viewed in exquisite detail, in vivo, and without the injection of exogenous dyes. However, commercial OCTA systems provide little information about actual erythrocyte speeds; instead, OCTA is typically used to visualize the presence and/or absence of vasculature. This is an important limitation because in many ocular diseases, including diabetic retinopathy (DR) and age-related macular degeneration (AMD), alterations in blood flow, but not necessarily only the presence or absence of vasculature, are thought to be important in understanding pathogenesis. To address this limitation, we have developed an algorithm, variable interscan time analysis (VISTA), which is capable of resolving different erythrocyte speeds. VISTA works by acquiring >2 repeated B-scans, and then computing multiple OCTA signals corresponding to different effective interscan times. The OCTA signals corresponding to different effective interscan times contain independent information about erythrocyte speed. In this study we provide a theoretical overview of VISTA, and investigate the utility of VISTA in studying blood flow alterations in ocular disease. OCTA-VISTA images of eyes with choroidal neovascularization, geographic atrophy, and diabetic retinopathy are presented.
Eric M. Moult, Stefan A. Ploner, WooJhon Choi, ByungKun Lee, Lennart A. Husvogt, Chen D. Lu, Eduardo Novais, Emily D. Cole, Benjamin M. Potsaid, Jay S. Duker, Joachim Hornegger, Andreas K. Meier, Nadia K. Waheed, and James G. Fujimoto, "Visualizing microvascular flow variation in OCTA using variable interscan time analysis (VISTA) (Conference Presentation)," Proc. SPIE 10053, Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XXI, 100530F (Presented at SPIE BiOS: January 30, 2017; Published: 19 April 2017); https://doi.org/10.1117/12.2254845.5371723130001.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon