March 2012
Volume 53, Issue 14
Free
ARVO Annual Meeting Abstract  |   March 2012
3-Dimensional Analysis of Distal Outflow Pathways in POAG Eyes at Low and High Perfusion Pressures
Author Affiliations & Notes
  • Cheryl R. Hann
    Ophthalmology,
    Mayo Clinic, Rochester, Minnesota
  • Andrew J. Vercnocke
    Physiology & Biomedical Engineering,
    Mayo Clinic, Rochester, Minnesota
  • Michael D. Bentley
    Biological Sciences, Minnesota State University, Mankato, Mankato, Minnesota
  • Michael P. Fautsch
    Ophthalmology,
    Mayo Clinic, Rochester, Minnesota
  • Footnotes
    Commercial Relationships  Cheryl R. Hann, None; Andrew J. Vercnocke, None; Michael D. Bentley, None; Michael P. Fautsch, None
  • Footnotes
    Support  NEI grant EY07065, Research to Prevent Blindness, and Mayo Foundation
Investigative Ophthalmology & Visual Science March 2012, Vol.53, 3273. doi:
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      Cheryl R. Hann, Andrew J. Vercnocke, Michael D. Bentley, Michael P. Fautsch; 3-Dimensional Analysis of Distal Outflow Pathways in POAG Eyes at Low and High Perfusion Pressures. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3273.

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

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Abstract

Purpose: : To compare the distal outflow pathways of primary open angle glaucoma (POAG) and normal eyes perfused at low (10 mmHg) and high (20 mmHg) pressures.

Methods: : Four pairs of human eyes (2 normal, ages 61 and 68 years; 2 POAG, ages 61 and 88 years) were obtained from the MN Lions Eye Bank. For each pair, eyes were perfused with phosphate buffered saline containing 5.5 mM glucose for 2 hours. One eye of each pair was perfused at 10 mmHg while the fellow eye was perfused at 20 mmHg. Eyes were fixed by anterior chamber exchange at like pressures with 4% paraformaldehyde/2% glutaraldehyde in 0.1 M phosphate followed by continuous perfusion with the same fixative for 8-12 hours. Quadrants were postfixed in osmium tetroxide, embedded in Epon Araldite, and scanned using 3-dimensional micro-computed tomography at 6 µm voxel resolution. Collector channels were enumerated and measured using ANALYZETM. Schlemm’s canal volume was measured in a stereology sub-program in ANALYZETM. Mean and standard deviation for each group was calculated.

Results: : At 10 mmHg, the number of identified collector channels were similar between POAG (4.6 ± 1.4 collector channels/quadrant) and normal eyes (4.8 ± 1.3 collector channels/quadrant). Collector channel orifice size was reduced in POAG (33.1 ± 11.9 µm) when compared to normal eyes (45.6 ± 12.1 µm). At 20 mmHg, the number of collector channels increased by 2.8-fold in normal (12.8 ± 6.7 collector channel/quadrant) and 2.0-fold in POAG eyes (9.0 ± 3.3 collector channel/quadrant). Collector channel orifice size was reduced by 24% in POAG eyes compared to normal eyes at both perfusion pressures. Schlemm's canal volume in POAG eyes was 3.2 fold (10 mmHg) and 2.4-fold (20 mmHg) smaller than normal eyes at comparable pressures. Occlusions, which were defined as thickened collector channel orifice walls, closure of collector channel, and/or flocculent material in Schlemm's canal adjacent to and blocking the collector channel orifices were observed 2.0-fold more frequently in POAG than normal eyes at 20 mmHg.

Conclusions: : The distal outflow pathway of POAG eyes has reduced outflow area due to decreased Schlemm's canal volume, smaller collector channel orifice diameter and increased number of collector channel occlusions.

Keywords: trabecular meshwork • outflow: trabecular meshwork • intraocular pressure 
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