title: Depth-dependent changes in collagen organization in the human peripapillary sclera.
abstract: OBJECTIVE
  The collagen structure of the human peripapillary sclera plays a significant role in determining optic nerve head (ONH) biomechanics, and is therefore of interest in the study of glaucoma. The aim of the current work was to map the anisotropic collagen structure of the normal human peripapillary sclera as a function of tissue depth.
  
  
  METHODS
  Wide-angle x-ray scattering was used to quantify collagen fibril orientation at 0.5 mm intervals across six 150 μm-thick serial sections through the peripapillary sclera of eight normal European-derived human eyes. Two structural parameters were measured: 1) the relative number of fibrils preferentially aligned at a given angle within the tissue plane, 2) the degree of collagen alignment (anisotropy).
  
  
  RESULTS
  The inner-most one-third of the peripapillary scleral stroma (nearest to the choroid) was characterised by collagen fibrils either randomly arranged or preferentially aligned radially with respect to the ONH. In contrast, the outer two-thirds of the tissue was dominated by a circumferential arrangement of collagen encircling the ONH. In all tissue regions the degree of collagen anisotropy peaked in the mid-stroma and progressively decreased towards the tissue surfaces, with the largest depth variations occurring in the inferior-nasal quadrant, and the smallest occurring in the superior-nasal quadrant.
  
  
  CONCLUSIONS
  Significant, region-specific variations in collagen structure are present in the human peripapillary sclera as a function of depth. In normal eyes, the circumferential collagen fibril architecture is most prominent in the outer two-thirds of the stroma, possibly as a mechanical adaption to more effectively support the lamina cribrosa at the level of its insertion into the scleral canal wall.
authors.affiliation: Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, United Kingdom.
authors.forename: Jacek K
authors.initials: JK
authors.lastname: Pijanka
authors.affiliation: Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, United Kingdom.
authors.forename: Martin T
authors.initials: MT
authors.lastname: Spang
authors.affiliation: Diamond Light Source, Didcot, United Kingdom.
authors.forename: Thomas
authors.initials: T
authors.lastname: Sorensen
authors.affiliation: Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio, United States of America.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America.
authors.forename: Thao D
authors.initials: TD
authors.lastname: Nguyen
authors.affiliation: Glaucoma Center of Excellence, Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Harry A
authors.initials: HA
authors.lastname: Quigley
authors.affiliation: Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, United Kingdom.
authors.forename: Craig
authors.initials: C
authors.lastname: Boote
mesh_terms: D000368:Aged; D016880:Anisotropy; D001696:Biomechanical Phenomena; D003094:Collagen / Q000378:metabolism*; D006801:Humans; D008875:Middle Aged; D008954:Models, Biological; D009898:Optic Disk / Q000378:metabolism / Q000503:physiopathology; D012590:Sclera / Q000378:metabolism*
chemical_list: D003094:Collagen