title: Human scleral structural stiffness increases more rapidly with age in donors of African descent compared to donors of European descent.
abstract: OBJECTIVE
  We tested the hypothesis that the variation of peripapillary scleral structural stiffness with age is different in donors of European (ED) and African (AD) descent.
  
  
  METHODS
  Posterior scleral shells from normal eyes from donors of European (n = 20 pairs; previously reported) and African (n = 9 pairs) descent aged 0 and 90 years old were inflation tested within 48 hours post mortem. Scleral shells were pressurized from 5 to 45 mm Hg and the full-field, 3-dimensional (3D) deformation of the outer surface was recorded at submicrometric accuracy using speckle interferometry (ESPI). Mean maximum principal (tensile) strain of the peripapillary and midperipheral regions surrounding the optic nerve head (ONH) were fit using a functional mixed effects model that accounts for intradonor variability, same-race correlation, and spatial autocorrelation to estimate the effect of race on the age-related changes in mechanical scleral strain.
  
  
  RESULTS
  Mechanical tensile strain significantly decreased with age in the peripapillary sclera in the African and European descent groups (P < 0.001), but the age-related stiffening was significantly greater in the African descent group (P < 0.05). Maximum principal strain in the peripapillary sclera was significantly higher than in the midperipheral sclera for both ethnic groups.
  
  
  CONCLUSIONS
  The sclera surrounding the ONH stiffens more rapidly with age in the African descent group compared to the European group. Stiffening of the peripapillary sclera with age may be related to the higher prevalence of glaucoma in the elderly and persons of African descent.
authors.affiliation: Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States.
authors.forename: Massimo A
authors.initials: MA
authors.lastname: Fazio
authors.affiliation: Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States.
authors.forename: Rafael
authors.initials: R
authors.lastname: Grytz
authors.affiliation: Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States.
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Morris
authors.affiliation: Department of Mechanical Engineering, University of Calabria, Calabria, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Bruno
authors.affiliation: Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Girkin
authors.affiliation: Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States.
authors.forename: J Crawford
authors.initials: JC
authors.lastname: Downs
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D044383:Black People; D002648:Child; D002675:Child, Preschool; D004548:Elasticity; D005260:Female; D005901:Glaucoma / Q000208:ethnology / Q000503:physiopathology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009017:Morbidity / Q000639:trends; D011379:Prognosis; D012590:Sclera / Q000503:physiopathology*; D014019:Tissue Donors; D014481:United States / Q000453:epidemiology; D044465:White People; D055815:Young Adult; D001741:Black or African American
keywords: aging; racial differences; scleral biomechanics