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Christine E. Parc, Douglas H. Johnson, Harilaos S. Brilakis; Giant Vacuoles Are Found Preferentially near Collector Channels. Invest. Ophthalmol. Vis. Sci. 2000;41(10):2984-2990.
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purpose. To determine whether giant vacuoles form preferentially near collector
channels or over regions of optically empty space within the
juxtacanalicular tissue (JCT).
methods. To assess the relationship between giant vacuoles and collector
channels, six eyes were perfused with phosphate-buffered saline (PBS)
at 20 mm Hg and then fixed by perfusion. Serial sections were cut in
the frontal plane and light microscopy used to count the number of
giant vacuoles per length of Schlemm’s canal. The number of giant
vacuoles between two adjacent collector channels was determined. To
assess the relationship between giant vacuoles and the ultrastructure
of the JCT, an additional seven eyes were perfused with PBS at 10 mm
Hg, fixed by perfusion, and examined by transmission electron
microscopy. The ultrastructural components of the JCT were quantitated
with an image analysis system.
results. Twice as many giant vacuoles were present in regions underlying
collector channels as in regions between channels (giant vacuoles per
histologic section: 14.0 ± 1.7 versus 7.3 ± 0.8, P = 0.01). Giant vacuoles occurred on both the
inner and outer walls of the canal but were more numerous on the inner
wall (9.1 ± 1.0 versus 2.6 ± 0.4, P <
0.001). No significant increase in optically empty space was found in
the JCT regions underlying giant vacuoles compared with regions with no
vacuoles (50.7% ± 2.3% versus 47.3% ± 2.5%, P = 0.09). Examination of the amount of optically empty space immediately
adjacent (within 1 μm) to the inner wall endothelial cells of the
canal did not reveal a significant difference between regions under
vacuoles and regions without giant vacuoles.
conclusions. Giant vacuoles are found preferentially near collector channels,
indicating that aqueous flow across the inner wall is sensitive to
downstream pressure. The variability in giant vacuole distribution
noted in previous studies is in part due to the distance of the
vacuoles from the collector channels. No distinct findings in the JCT
were associated with the presence of giant
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