Optic nerve head blood flow autoregulation during isometric exercise in primary open‐angle glaucoma assessed by laser speckle flowgraphy

PURPOSE: To assess optic nerve head blood flow (ONHBF) autoregulation in patients with early- to moderate-stage primary open-angle glaucoma (POAG) and age- and sex-matched healthy controls using laser speckle flowgraphy (LSFG) and isometric handgrip exercise. METHODS: In this single-centre cross-sectional study, 26 patients with early- to moderate-stage POAG and 28 age- and sex-matched healthy controls were included. ONHBF was measured using LSFG at baseline, during isometric handgrip exercise, and after recovery. Mean arterial pressure (MAP) was recorded at each measurement time point. The relative change in ONHBF during handgrip (ΔBF) and a recovery index (RI) were calculated. Structural and vascular parameters including retinal nerve fibre layer thickness (RNFLT), retinal vessel diameters, and optical coherence tomography (OCT)-angiography-derived vessel density were assessed. RESULTS: Glaucoma patients exhibited significantly lower RNFLT, ONHBF parameters, central retinal artery and vein equivalents, and selected vessel density parameters compared with controls (all p < 0.05). During isometric exercise, MAP increased similarly in both groups (glaucoma: +16 ± 11%; controls: +15 ± 8%; both p < 0.001 vs. baseline; p = 0.981 between groups). However, ONHBF increased significantly more in glaucoma patients (23 ± 16%) than in controls (6 ± 13%) (p = 0.001, group-by-time interaction). The RI did not differ significantly between groups (p = 0.132). CONCLUSION: Patients with early- to moderate-stage POAG exhibit an altered ONHBF response to isometric exercise despite a comparable increase in systemic blood pressure, suggesting impaired vascular autoregulatory capacity. LSFG combined with handgrip stimulation provides a feasible approach for assessing vascular regulation in glaucoma. TRIAL REGISTRATION: ClinicalTrials.gov ID: NCT04596826.