April 2014
Volume 55, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2014
Peripapillary Sclera (PPS) Collagen Fiber Crimp Period Increases with Distance from the Optic Nerve Head (ONH)
Author Affiliations & Notes
  • Celeste Gomez
    UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA
    Department of Biological Sciences,The Dietrich School of Arts and Sciences, University of Pittsburgh, Pittsburgh, PA
  • Ning-Jiun Jan
    UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA
    Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA
  • Huong Tran
    UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA
    Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA
  • Jonathan L Grimm
    UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA
  • Kira L Lathrop
    UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA
    Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA
  • Gadi Wollstein
    UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA
    Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA
  • Hiroshi Ishikawa
    UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA
    Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA
  • Joel S Schuman
    UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA
    Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA
  • Larry Kagemann
    UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA
    Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA
  • Ian A Sigal
    UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA
    Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA
  • Footnotes
    Commercial Relationships Celeste Gomez, None; Ning-Jiun Jan, None; Huong Tran, None; Jonathan Grimm, None; Kira Lathrop, None; Gadi Wollstein, None; Hiroshi Ishikawa, None; Joel Schuman, Zeiss (P); Larry Kagemann, None; Ian Sigal, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science April 2014, Vol.55, 4258. doi:
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      Celeste Gomez, Ning-Jiun Jan, Huong Tran, Jonathan L Grimm, Kira L Lathrop, Gadi Wollstein, Hiroshi Ishikawa, Joel S Schuman, Larry Kagemann, Ian A Sigal; Peripapillary Sclera (PPS) Collagen Fiber Crimp Period Increases with Distance from the Optic Nerve Head (ONH). Invest. Ophthalmol. Vis. Sci. 2014;55(13):4258.

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

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Abstract
 
Purpose
 

The biomechanical sensitivity of the ONH to intraocular pressure (IOP) depends strongly on the properties of the sclera, especially the PPS. A primary cause of the nonlinear properties of the sclera is the waviness, or crimp, of the constitutive collagen fibers. Our goal was to measure the dependence of PPS collagen fiber crimp period on distance from the ONH.

 
Methods
 

Six eyes of three sheep (<2 years) were fixed at 5mmHg overnight using gravity perfusion fixation (cannula in the anterior chamber) and immersion fixation (10% formalin). Following fixation, the ONH and surrounding sclera were excised and cryosectioned coronally (30µm). Sections through the lamina cribrosa were selected and image mosaics of the whole section acquired using light microscopy (Nikon, 10x objective, 0.5 NA, 0.803 µm/pixel). The crimp period (averaged over 3 consecutive periods) was then measured manually (Fiji) in PPS regions proximal (<900µm) and distal (1400-3000µm) to the ONH (>10 measurements per region, 30-48 measurements per eye). A linear mixed-effect model was fit to the data accounting for multiple measurements in each eye and correlation between contralateral eyes.

 
Results
 

Distal crimp period was significantly larger than the proximal crimp period (p < 0.001, Table and Figure). Over the 6 eyes crimp periods were (mean ± SD): 39.4±6.1 µm for proximal sclera and 65.1±18.8 µm for distal sclera.

 
Conclusions
 

The 50% difference in crimp period between the distal and proximal PPS regions denotes potentially different biomechanical properties between these regions, although the consequences of this are not yet known. The proximal region encompasses a ring of fibers circumferential to the ONH, and a smaller crimp period therein may provide biomechanical stability and a more uniform distribution of deformations in response to loading, protecting the ONH from insult.

 
 
TABLE 1. Mean (SD) crimp periods per eye in distal and proximal regions to ONH
 
TABLE 1. Mean (SD) crimp periods per eye in distal and proximal regions to ONH
 
 
FIG 1. Close-ups of proximal (B) and distal (C) PPS of eye 1A. The colors represent the local collagen orientation relative to the fibers in the surrounding area, such that collagen fibers curved in one direction are yellow and purple in the other (A). Fiber orientations were determined as described previously (IOVS 2013 54:65). The larger crimp period in the distal region (C) is visible in the thicker yellow-purple bands as compared with the proximal region (B).
 
FIG 1. Close-ups of proximal (B) and distal (C) PPS of eye 1A. The colors represent the local collagen orientation relative to the fibers in the surrounding area, such that collagen fibers curved in one direction are yellow and purple in the other (A). Fiber orientations were determined as described previously (IOVS 2013 54:65). The larger crimp period in the distal region (C) is visible in the thicker yellow-purple bands as compared with the proximal region (B).
 
Keywords: 708 sclera • 577 lamina cribrosa • 599 microscopy: light/fluorescence/immunohistochemistry  
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