June 2023
Volume 64, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2023
Comparison of Giant Vacuoles in the Inner Wall Endothelium of Schlemm’s Canal in Human Eyes between High and Physiologic Pressures
Author Affiliations & Notes
  • Isaac Goodman
    Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
  • Varun Bhalla
    Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
  • Benjamin Soares
    Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
  • Thuy D. Le
    Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
  • David L Swain
    Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
    Anatomy and Neurobiology, Boston University School of Medicine, Boston, Massachusetts, United States
  • Tate Valero
    Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
  • Irving Zhao
    Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
  • Haiyan Gong
    Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States
    Anatomy and Neurobiology, Boston University School of Medicine, Boston, Massachusetts, United States
  • Footnotes
    Commercial Relationships   Isaac Goodman None; Varun Bhalla None; Benjamin Soares None; Thuy D. Le None; David Swain None; Tate Valero None; Irving Zhao None; Haiyan Gong None
  • Footnotes
    Support  National Institute of Health (NIH) EY022634, The Massachusetts Lions Eye Research Fund
Investigative Ophthalmology & Visual Science June 2023, Vol.64, 1885. doi:
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      Isaac Goodman, Varun Bhalla, Benjamin Soares, Thuy D. Le, David L Swain, Tate Valero, Irving Zhao, Haiyan Gong; Comparison of Giant Vacuoles in the Inner Wall Endothelium of Schlemm’s Canal in Human Eyes between High and Physiologic Pressures. Invest. Ophthalmol. Vis. Sci. 2023;64(8):1885.

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

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Abstract

Purpose : This study investigated the morphologic differences between giant vacuoles (GVs) in the inner wall endothelium of Schlemm’s canal (SC) in human eyes perfused at 30 or 7 mmHg (physiologic pressure in enucleated eyes) using serial block-face scanning electron microscopy (SBF-SEM) and 3D reconstruction.

Methods : Four normal human eyes were perfused at 30 (n=2) or 7 mmHg (n=2) with fluorescent tracers to mark regions of active flow, followed by perfusion-fixation. Tissue wedges (n=12) of trabecular meshwork including SC from high-, low-, and non-flow areas of each eye, guided by tracer distribution, were dissected and processed for SBF-SEM. GVs types were identified (Type I: no basal opening or I-pore, Type II: basal opening, no I-pore, Type III: I-pore, no basal opening, and Type IV: basal opening and I-pore). Types and spans of GVs were compared by analyzing 19047 SBF-SEM images between 7 (n=9586) and 30 mmHg (n=9461) using Reconstruct. Volumes of GVs from a random subset were measured using 3D reconstruction. Statistical analysis comparing data between the two pressures was performed using R.

Results : There were more GVs found at 30 mmHg (n=1541) when compared to 7 mmHg (n=1312). There were more Type IV GVs at 30 mmHg when compared to 7 mmHg (p < 0.01). Type IV GVs occurred most frequently in high flow areas at both pressures. At both pressures, GVs with I-pores were greater in size (both span and volume) than GVs without I-pores in all flow areas (p < 0.01). Type IV GVs were larger than Type II GVs, which were larger than Type I GVs at both pressures (p < 0.01). The span of GVs without I-pores was significantly greater at 7 mmHg (p < 0.01). However, there was no significant difference between the volumes of GVs with or without I-pores between the two pressures.

Conclusions : The size of GVs with I-pores was significantly larger than the GVs without I-pores in all flow areas of both pressures, supporting that GV size is an important contributing factor for I-pore formation. The differences in span but not volume of GVs without I-pores between two pressures suggest that GVs at high pressure appears more convex in shape and protrudes further into SC, which may contribute to thinning of lining cellular membrane of GVs. More Type IV GVs in the high-flow areas at both pressures suggest that changing percentage of Type IV GVs plays a role in regulating segmental flow.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

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