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H. Gong, T. F. Freddo, Y. Zhang; New Morphological Findings in Primary Open-Angle Glaucoma. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2079.
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We previously reported that elevation of intraocular pressure (IOP) leads to a progressive collapse of the aqueous plexus near the collector channel ostia in non-human eyes. But an important additional factor, not previously recognized, is the progressive herniation of the inner wall and juxtacanalicular tissue (JCT) into the collector channel ostia. Herniations confine flow to the region, resulting in a reduced area available for outflow across the inner wall. These herniations were reversible when IOP was reduced. This finding may partly explain the IOP associated increase in outflow resistance (ARVO 2005, ICER 2006) where we demonstrated that herniations of inner wall and JCT into collector channels ostia are morphological correlates of increased outflow resistance following an acute increase in IOP. The goal of this study was to determine whether the presence or absence of herniations can be used to distinguish eyes with primary open-angle glaucoma (POAG) from normal human eyes.
Four glaucomatous eyes (78-79 years) and four normal human eye-bank eyes (58 - 89 years) were immersion-fixed with Karnovsky’s fixative. Two glaucomatous eyes were perfusion-fixed at 10 mmHg. Tissues from 4 quadrants of each eye were processed for light microscopy. Sections were cut tangential to the limbus and perpendicular to the ocular surface. At least eight ostia regions per eye were examined for herniations within the ostia.
Partial collapse of Schlemm’s canal, especially near collector channel ostia regions, and focal herniations of the inner wall and JCT into collector channel ostia were detected in all glaucomatous eyes. Fifty-eight collector channel ostia regions of POAG eyes fixed at 0 mmHg were examined with forty-six showing herniations (79%). Twenty-seven collector channel ostia regions of POAG eyes perfusion-fixed at 10 mmHg were examined and herniations were found in 100% of the regions. However, in normal eyes, fifty-three collector channel ostia regions of normal eyes fixed at 0 mmHg were examined and six herniations were found (11%). There was a significant difference between the POAG and normal human eyes (p<0.005).
Our data suggest that normal eyes develop reversible herniations into collector channel ostia with acute elevations of pressure. These herniations appear to be permanent and a regular feature of eyes with POAG.
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