title: Eye-specific IOP-induced displacements and deformations of human lamina cribrosa.
abstract: OBJECTIVE
  To measure high-resolution eye-specific displacements and deformations induced within the human LC microstructure by an acute increase in IOP.
  
  
  METHODS
  Six eyes from donors aged 23 to 82 were scanned using second harmonic-generated (SHG) imaging at various levels of IOP from 10 to 50 mm Hg. An image registration technique was developed, tested, and used to find the deformation mapping between maximum intensity projection images acquired at low and elevated IOP. The mappings were analyzed to determine the magnitude and distribution of the IOP-induced displacements and deformations and contralateral similarity.
  
  
  RESULTS
  Images of the LC were obtained and the registration technique was successful. IOP increases produced substantial, and potentially biologically significant, levels of in-plane LC stretch and compression (reaching 10%-25% medians and 20%-30% 75th percentiles). Deformations were sometimes highly focal and concentrated in regions as small as a few pores. Regions of largest displacement, stretch, compression, and shear did not colocalize. Displacements and strains were not normally distributed. Contralateral eyes did not always have more similar responses to IOP than unrelated eyes. Under elevated IOP, some LC regions were under bi-axial stretch, others under bi-axial compression.
  
  
  CONCLUSIONS
  We obtained eye-specific measurements of the complex effects of IOP on the LC with unprecedented resolution in uncut and unfixed human eyes. Our technique was robust to electronic and speckle noise. Elevated IOP produced substantial in-plane LC stretch and compression. Further research will explore the effects of IOP on the LC in a three-dimensional framework.
authors: Department of Ophthalmology, UPMC Eye Center, Ophthalmology and Visual Science Research Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
authors: Ian A
authors: IA
authors: Sigal
authors: Jonathan L
authors: JL
authors: Grimm
authors: Ning-Jiun
authors: NJ
authors: Jan
authors: Korey
authors: K
authors: Reid
authors: Don S
authors: DS
authors: Minckler
authors: Donald J
authors: DJ
authors: Brown
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D003941:Diagnostic Techniques, Ophthalmological; D005901:Glaucoma / Q000150:complications / Q000503:physiopathology*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008875:Middle Aged; D009898:Optic Disk / Q000503:physiopathology*; D009901:Optic Nerve Diseases / Q000209:etiology / Q000503:physiopathology*; D055815:Young Adult
keywords: biomechanics; glaucoma; lamina cribrosa; optic nerve head; second harmonic imaging; strain