Purpose: To compare glaucoma severity with ocular microcirculation, measured with either laser speckle flowgraphy (LSFG) or optical coherence tomography angiography (OCTA). Methods: We retrospectively studied 82 eyes of 82 open-angle glaucoma (OAG) patients who underwent same-day LSFG and OCTA examinations, with 20 eyes of 20 healthy subjects as controls. In OCTA images, vessel density (VD) (%) was calculated in concentric regions (regions 1, 2 and 3: R1, R2 and R3, respectively) defined by 1.6-, 3.2- and 3.6-mm-diameter circles around the optic nerve head (ONH). In R3, the large vessels were automatically masked to calculate pure capillary density (auto R3 VD). LSFG-measured mean blur rate (MBR) was examined in the overall ONH (MA), vessel-area ONH (MV) and tissue-area ONH (MT). Results: Auto R3 VD had high reproducibility (coefficient of variation: 1.65–3.88%) and accurately reflected manual R3 VD [mean bias: −0.0087% (auto R3 VD – manual R3 VD)]. MA and MT decreased significantly with OAG severity, especially in the early OAG stages (control vs. mild: p = 0.003 and p < 0.001, respectively). R1 VD did not change with severity. R2 and auto R3 VD decreased significantly with OAG severity, especially in the severe stages (R2, mild vs. severe: p = 0.008; auto R3 VD, mild vs. severe: p < 0.001, moderate vs. severe: p = 0.028). Conclusion: Optical coherence tomography angiography-derived auto R3 VD is novel, reproducible and accurately reflects manual measurements. It is useful for differentiating moderate and advanced glaucoma, while LSFG-derived MT is useful for identifying early glaucoma.
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