June 2015
Volume 56, Issue 7
ARVO Annual Meeting Abstract  |   June 2015
Morphological Changes in the Distal Outflow Pathway of Primary Open Angle Glaucoma
Author Affiliations & Notes
  • Haiyan Gong
    Ophthalmology, Boston Univ School of Medicine, Boston, MA
  • Varun Gorantla
    Ophthalmology, Boston Univ School of Medicine, Boston, MA
  • Yuyan Zhang
    Ophthalmology, Huashan Hospital of Fudan University, Shanghai, China
  • Thomas F Freddo
    University of Waterloo School of Optometry, Waterloo, ON, Canada
  • David Swain
    Ophthalmology, Boston Univ School of Medicine, Boston, MA
  • Footnotes
    Commercial Relationships Haiyan Gong, None; Varun Gorantla, None; Yuyan Zhang, None; Thomas Freddo, None; David Swain, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2015, Vol.56, 3300. doi:
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      Haiyan Gong, Varun Gorantla, Yuyan Zhang, Thomas F Freddo, David Swain; Morphological Changes in the Distal Outflow Pathway of Primary Open Angle Glaucoma. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3300.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: To compare the morphological changes in the distal outflow pathway between primary open angle glaucoma (POAG) and age-matched normal eyes, with an emphasis on the changes near the collector channel (CC) ostia.

Methods: Six POAG and six age-matched normal human eyes were immersion-fixed with Karnovsky’s fixative. Tissues from all quadrants of each eye were processed for light microscopy. Serial frontal sections were cut, stained, and imaged. Widths of Schlemm’s canal (SC) and CC ostia, number of herniations into the CC ostia, as well as the difference in amount of pigment, which was used as an internal marker for preferential flow, in the areas of the trabecular meshwork (TM) near CC ostia regions, with or without herniations, were analyzed between POAG and normal eyes. Two-tailed Student’s t-test was used for statistical analysis with a required significance level of 0.05.

Results: In normal eyes, SC was significantly wider near CC ostia when compared to SC away from CC ostia. This difference was not observed in POAG eyes. Average widths of SC (11.89 ± 7.29 μm in POAG vs. 21.00 ± 7.87 μm in normal, p< 0.0001) and CC ostia (31.55 ± 18.89 μm in POAG vs. 42.15 ± 14.48 μm in normal, p= 0.0017) were significantly narrower in POAG eyes compared to controls. Interestingly, significantly narrower CC ostia were found in POAG eyes in the other three quadrants but not nasal quadrant compared to normal eyes. There were significantly more herniations, especially complete herniations, obstructing CC ostia in POAG (61%) eyes compared to controls (14%, p<0.0001). There was more pigment in the areas of the TM near CC ostia than the areas where CC ostia were not present in normal eyes. Statistically less pigment (p<0.0001) was observed in the TM that completely herniated into the CC ostia.

Conclusions: Compared to normal controls, POAG eyes showed a decrease in the widths of SC and CC ostia and more herniations that partially or completely obstructed the CC ostia. In addition, a decrease in pigment was found in the TM that herniated into CC ostia. These morphological findings suggest diminished outflow at the herniated CC ostia regions, which likely contribute to the increased outflow resistance and consequent elevated IOP in POAG eyes.


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