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Michael D. Bentley, Cheryl R. Hann, Michael P. Fautsch; Anatomical Diversity of Human Collector Channel Orifice Structure. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3234.
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To investigate the surface morphology of collector channel orifices in relation to that of Schlemm’s canal in normal eyes.
Four normal eyes from four different donors (ages 53-73) were fixed under varying paraformaldehyde conditions. Anterior segments from all 4 eyes were dissected into radial wedges containing Schlemm's canal and collector channels. Schlemm's canal inner and outer walls were dissected from each wedge and rinsed in 0.1 M phosphate, dehydrated in graded acetone solutions (50-100%), critical point dried, sputter coated with gold and scanned using a JEOL 6510 scanning electron microscope. A total of 15 collector channels from 12 wedges were examined.
Schlemm's canal appeared to be an anastomosing network of pathways, partially separated by septal columns. In the area surrounding collector channel orifices, Schlemm's canal assumed a groove configuration, which appeared to direct flow into the orifice. Collector channels appeared in several configurations: simple oval openings, oval openings with endothelial bridges, and oval openings with tethered, cusp-like flaps. Regardless of appearance, the orifice diameters ranged between 30-70 µm. Five of the 12 wedges contained multiple collector channels located within 130-380 µm of one another. Most orifices were associated with either 30-50 µm wide bridges or flap-like configurations. The bridges and flaps were polygonal in shape, 8-10 µm thick, and had endothelial cell surfaces. Endothelial-lined tethers connected the bridges and flaps to the outer wall in a fanlike appearance. Seven of 15 collector channel orifices examined had either endothelial lined bridges or flap-like structures. Collector channel orifice structure was unaffected by differences in fixation.
Collector channel orifices have a variety of morphologies with nearly half containing a bridge and flap configuration which may act as a valve-like structure to promote aqueous fluid drainage into collector channels.
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