To study AHO structure in living subjects, anterior segment optical coherence tomography (OCT) has been indispensable. Like 3D micro-CT, AHO lumens appeared as regions of low reflectivity on OCT scans (Figure 1). Spectral domain OCT (SD-OCT) successfully identified the TM, SC, collectors channels and intrascleral venous plexus. Image processing allowed for creation of three-dimensional in silico casts of small segments of distal AHO pathways in normal individuals . Pilocarpine in live patients (Skaat et al. IOVS 2014; 55: ARVO Abstract 5682) and mice has been reported to increase the size of these AHO lumens while IOP elevation has been shown to do the opposite . Automated segmentation has been proposed (Murakami Y et al. IOVS 2014; 55: ARVO Abstract 927).