Dysregulation of retinal and optic nerve blood flow is implicated in glaucoma pathogenesis. Kotliar et al. (672) compared real-time dynamic changes in the diameter of retinal arterioles in open-angle glaucoma patients and age-matched controls using a commercially available retinal vessel analyzer (RVA). Although there were no differences in baseline measurements between the 14 glaucoma subjects (treated and untreated) and 13 age-matched controls, there were differences in artery diameter profiles, in response to IOP elevation (suction cup) at 35 mmHg pressures that exceeded systolic blood pressure. The authors devised 'high frequency waviness' as a parameter that describes changes in the longitudinal profile of arterial caliber over time. In glaucoma patients, successive contraction and dilation of arteriolar caliber, after IOP elevation, generated a wave profile that had a higher frequency compared to the response in age-matched controls. These findings are intriguing, as changes in vessel diameter may reflect loss of local autoregulation due to endothelial cell dysfunction or even reflect changes in local metabolic demand. Further work is now required in larger cohorts to confirm these findings and also determine the underlying mechanisms that regulate retinal blood vessel caliber and the vascular response to IOP elevation.