Abstract
Purpose: :
To investigate the surface morphology of collector channel orifices in relation to that of Schlemm’s canal in normal eyes.
Methods: :
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.
Results: :
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.
Conclusions: :
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.
Keywords: trabecular meshwork • outflow: trabecular meshwork • intraocular pressure