Application value of choroidal capillary blood flow signal defect in ophthalmic diseases

Optical coherence tomography angiography (OCTA) is a non-invasive imaging technique that displays fundus blood vessels.Choroidal capillary (CC) is the intraocular tissue with the highest blood perfusion, and its pathological changes are closely related to the occurrence and progression of many retinal and choroidal diseases.Binarization of OCTA-scanned CC images can obtain images with alternating light and dark areas.The dark area represents that the blood flow signal in this area is lower than the detectable lowest resolution, and is defined as choriocapillaris flow deficit (CC FD). Further calculation can obtain the percentage of CC FD, the number of CC FD, CC FD average area and other related quantitative indicators.CC FD-related quantitative indicators are objective and reliable to evaluate the CC structure and perfusion status, thus can be used to predict the progress and prognosis of chorioretinal diseases and provide important reference for the diagnosis, treatment and prognosis of various eye diseases such as age-related macular degeneration, central serous chorioretinopathy and myopia.However, CC FD can be affected by interfering factors like age, scanning range and blood pressure.Besides, there are still several limitations in processing CC images.Therefore, we need to understand and use it correctly.This review summarizes the measurements, influencing factors and application of CC FD-related quantitative indicators obtained by OCTA in different eye diseases and systemic diseases.

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