OSLI Retina

December 2016

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Practical Retina Incorporating current trials and technology into clinical practice December 2016 ยท Vol. 47, No. 12 1081 Evaluation of the Retinal and Choroidal Vasculature With OCT Angiography Versus Conventional Angiography by Colin S. Tan, MBBS, MMed (Ophth), FRCSEd (Ophth), Louis W. Lim, MBBS, and SriniVas R. Sadda, MD The role of optical coherence tomogra- phy angiography (OCTA) in the evalu- ation of the retinal and choroidal vas- culature is still evolving as we learn more about this fascinating technolo- gy. Since 2015, we have seen numer- ous papers pub- lished comparing OCTA to conven- tional fluorescein angiography (FA) and indocyanine green angiography (ICGA) to evalu- ate various disease states. Retina spe- cialists are trying to process this flood of data as we lack a review of the literature regarding this topic. I asked Colin S. Tan, MBBS, MMed (Ophth), FRCSEd (Ophth), Louis W. Lim, MBBS, and SriniVas R. Sadda, MD, to provide us with an overview of the merits of each OCTA, FA, and ICGA in evaluating various retinal and choroidal diseases as well as oth- er widely recognized retinal vascular features. They will also summarize for us the pros and cons of each of the three angiography methods. Obviously, OCTA is a very useful technology and its role will only in- crease as advances in processing algo- rithms continue. The insights and ex- pertise that Drs. Tan, Lim, and Sadda share with us will be very helpful as we apply OCTA into our clinical prac- tices. Optical coherence tomography angiography (OCTA) is an exciting new technology that promises to revolutionize the imaging of patients with various ocular conditions. OCT scans provide high-resolution structural detail of the retina and choroid. In contrast, OCTA allows visualization of blood flow within the layers of the retina and choriocapillaris. 1,2 OCTA is based on the premise that blood corpuscles are moving within retinal vessels, whereas the surrounding structures are not. 1,2 Stationary tissue shows high correlation in imaging characteristics from one frame to the next, whereas blood flowing through vessels causes changes in reflectance over time and localized areas of low correlation between frames. The motion of blood within vessels can be detected using phase/Doppler shift, amplitude variation, or a combination of these. OCTA uses rapidly performed OCT B-scans at the same location to analyze for variation, and processing algorithms then create vascular flow maps of the region. The advantage of OCTA is that it is a rapid, noninvasive, dyeless system that allows simultaneous assessment of structure and flow with better microvascular and depth resolution than conventional angiograms. In contrast, conventional angiograms require intravenous access, and fluorescein and indocyanine Colin S. Tan Louis W. Lim SriniVas R. Sadda doi: 10.3928/23258160-20161130-01 Seenu M. Hariprasad Practical Retina Co-Editor

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