For a more global AHO assessment, larger and fluorescently tagged tracers were delivered into either live or enucleated eyes in several species. Fluorescent microspheres ranged in size from 0.2 to 20 microns [22,44,47–51]. Alternatively, 0.01 micron quantum dots were used . Imaging was done with laboratory fluorescent or confocal microscopes. Segmental patterns were seen, and combining tracer studies with histology, estimates of TM utilization could be calculated from a percent effective filtration length . Two color tracer studies allowed for demonstrating reduced AHO with increasing IOP . Tracer collection in the TM localized near collector channels in enucleated human eyes .