Ocular microcirculation measurement with laser speckle flowgraphy and optical coherence tomography angiography in glaucoma

Abstract

To compare glaucoma severity with ocular microcirculation, measured with either laser speckle flowgraphy (LSFG) or optical coherence tomography angiography (OCTA). 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). 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). 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.