title: Optical rheology of porcine sclera by birefringence imaging.
abstract: OBJECTIVE
  To investigate a relationship between birefringence and elasticity of porcine sclera ex vivo using polarization-sensitive optical coherence tomography (PS-OCT).
  
  
  METHODS
  Elastic parameters and birefringence of 19 porcine eyes were measured. Four pieces of scleral strips which were parallel to the limbus, with a width of 4 mm, were dissected from the optic nerve head to the temporal side of each porcine eye. Birefringence of the sclera was measured with a prototype PS-OCT. The strain and force were measured with a uniaxial material tester as the sample was stretched with a speed of 1.8 mm/min after preconditioning. A derivative of the exponentially-fitted stress-strain curve at 0% strain was extracted as the tangent modulus. Power of exponential stress-strain function was also extracted from the fitting. To consider a net stiffness of sclera, structural stiffness was calculated as a product of tangent modulus and thickness. Correlations between birefringence and these elastic parameters were examined.
  
  
  RESULTS
  Statistically significant correlations between birefringence and all of the elastic parameters were found at 2 central positions. Structural stiffness and power of exponential stress-strain function were correlated with birefringence at the position near the optic nerve head. No correlation was found at the position near the equator.
  
  
  CONCLUSIONS
  The evidence of correlations between birefringence and elasticity of sclera tested uniaxially was shown for the first time. This work may become a basis for in vivo measurement of scleral biomechanics using PS-OCT.
authors.affiliation: Computational Optics Group in the University of Tsukuba, Tsukuba, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamanari
authors.forename: Kotaro
authors.initials: K
authors.lastname: Ishii
authors.forename: Shinichi
authors.initials: S
authors.lastname: Fukuda
authors.forename: Yiheng
authors.initials: Y
authors.lastname: Lim
authors.forename: Lian
authors.initials: L
authors.lastname: Duan
authors.forename: Shuichi
authors.initials: S
authors.lastname: Makita
authors.forename: Masahiro
authors.initials: M
authors.lastname: Miura
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Oshika
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Yasuno
mesh_terms: D000818:Animals; D001718:Birefringence; D004210:Dissection; D004548:Elasticity; D012212:Rheology / Q000379:methods*; D012590:Sclera / Q000033:anatomy & histology*; D034421:Sus scrofa; D041623:Tomography, Optical Coherence / Q000379:methods*