A Superpixel-Histogram Method to Analyze Retinal, Optic Nerve, and Choroidal Blood Flow Using Laser Speckle Flowgraphy

Laser speckle flowgraphy (LSFG) is a non-invasive imaging technology for quantifying microvascular blood flow. In the eye, LSFG quantifies the relative dynamics of blood flow of the retina, choroid and optic nerve head on a continuous scale. Currently, LSFG analysis requires the placement of "rubber bands" (defining regions of interest) to measure blood flow at desired locations. However, the placement of rubber bands requires knowledge of which regions are likely to be affected by disease. Here, we demonstrate a fully automated superpixel-histogram method without rubber band placement to determine regional blood flow abnormalities. Regional blood flow patterns were quantified via superpixel distributions of mean blur rate (MBR, linearly proportional to blood flow) and percentages of total superpixels at five pre-defined ranges of blood flow. We applied the proposed method to help diagnose acute arteritic anterior ischemic optic neuropathy (AAION) and found that compared to normal eyes, acute AAION eyes showed a significant blood flow reduction of the choroid due to the effect of giant cell arteritis on the posterior ciliary arteries (supplying the choroid and optic nerve circulation). The proposed method demonstrated a novel approach for quantifying abnormal regions of blood flow in different vascular beds caused by disease.