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Elizabeth Martin, Yi Jiang, Steven Padilla, Ronald L Fellman, Zhehai Zhou, Ruikang K Wang, Murray A Johnstone; Scanning electron microscopy to characterize collector channel anatomic relationships in a non-glaucomatous human eye.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3259.
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© ARVO (1962-2015); The Authors (2016-present)
To determine if the anatomic relationship between collector channel ostia (CCO) and their adjacent intrascleral collector channels (ISCC) is compatible with OCT observed pressure-dependent structural motion.
Eye of a 73 y/o W/M <24 hour postmortem dissected into 4 limbal quadrants, each having a 130 um cannula inserted into both ends of Schlemm’s canal (SC). Toluidine blue staining of viscoelastic permitted visual confirmation of filling the length of SC. Fixation was followed by tilted frontal sectioning that bisected the long axis of SC. To avoid double counting of bisected structures only the corneal ½ of each bisected segment was imaged. SEM preparation was done by dehydration, osmium, tannic acid, uranyl acetate, critical point drying and sputtering. Images were measured using ImageJ software.
Sections/quadrant: 9, 9, 11, 11 for IT, IN, ST, SN respectively. (See Fig. 1 & 2) SC data: total length measured, 30,116 μm; mean SC segment length, 752±150 μm (range (R) 392-1069 μm); mean SC height at cut front edge perpendicular to long axis, 69.5±23.6 μm (R 34.3-134.5); mean SC area 51,687±21,760 μm. CCO data: n=10. Mean height perpendicular to SC, 13.9±6.6 μm (R 6.0-28.4); length parallel to SC 44.3±24.9 μm (R 17.8-88.9); mean area 570.8±494.9 um. ISCC Data: Distance from SC, 100.2±50.9 μm (R 6.4-221.8); mean ISCC height, 21.9±11.5 μm (R 8.3-64.4); mean length, 150.6±113.8 μm (R 35.4-691); Mean aspect ratio, 7.3 ±4.6 μm (R 1.6-29.5). Mean ISCC angle subtended from SC outer wall 9.5± 9.80 (R 0.0-51.7). CCO extended a mean of 13.9 μm & maximum of 28 μm into the sclera before abruptly turning circumferentially to join nearby ISCCs creating a flap-like relationship of collagen septum at CCO. ISCCs course nearly parallel to SC. The resultant elongated septa partition the ISCC from SC with a mean 100.4 μm thickness and a 7.3 mean aspect ratio.
The organization of the CCO with their flap-like entrance septa and the long thin septa between SC and ISCC create geometric relationships that favor pressure-dependent motion. The structural relationships provide an explanation for recent OCT evidence of pressure-dependent motion of the CCO and ISCC areas.
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