title: Differences in the region- and depth-dependent microstructural organization in normal versus glaucomatous human posterior sclerae.
abstract: OBJECTIVE
  This study quantitatively investigated differences in the regional- and depth-dependent human posterior scleral microstructure in glaucomatous (G) and nonglaucomatous (NG) donors.
  
  
  METHODS
  Twenty-five posterior poles from six G and seven NG donors were analyzed using small angle light scattering (SALS) to investigate the organization of scleral fibers around the optic nerve head. Eccentricity (Ecc), fiber splay (FS), and percent equatorial fibers (PEF) were quantified.
  
  
  RESULTS
  Regional statistically significant differences between G and NG groups existed in Ecc (P < 0.0001), FS (P < 0.005), and PEF (P < 0.005). Distinct and substantial variation through the depth occurred in all three end points. Region-specific differences in Ecc existed at the episcleral surface; however, by 40% into the depth, all regions converged to a similar value. Fiber splay increased in all regions by an average of 0.14 from the episcleral surface to the intraocular surface. The percentage of equatorial fibers decreased universally through the depth from approximately 61% to 33%. Generally, the inferior and superior regions had a lower Ecc and PEF compared to the nasal and temporal regions.
  
  
  CONCLUSIONS
  Region and depth of the posterior sclera are important factors that should be included when comparing scleral microstructure of G and NG tissue in experimental and computational work. The dramatic changes in the depth of the sclera may represent baseline properties that affect predisposition to primary open angle glaucoma (POAG), and necessitate that further research include depth as a factor in assessing how observed structural differences contribute to or are a result of POAG.
authors.affiliation: Department of Aerospace and Mechanical Engineering, University of Arizona, Tucson, Arizona.
authors.forename: Forest L
authors.initials: FL
authors.lastname: Danford
authors.forename: Dongmei
authors.initials: D
authors.lastname: Yan
authors.forename: Robert A
authors.initials: RA
authors.lastname: Dreier
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Cahir
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Girkin
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Vande Geest
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D005260:Female; D005901:Glaucoma / Q000473:pathology* / Q000503:physiopathology; D006801:Humans; D007429:Intraocular Pressure; D008027:Light; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D009898:Optic Disk / Q000473:pathology; D053838:Scattering, Small Angle; D012590:Sclera / Q000648:ultrastructure*; D055815:Young Adult
keywords: POAG; biomechanics; dependent; depth; glaucoma; glaucomatous; human; microstructure; nonglaucomatous; region; sclera