title: Effect of acute intraocular pressure elevation on the monkey optic nerve head as detected by spectral domain optical coherence tomography.
abstract: OBJECTIVE
  To determine whether acutely elevated IOP alters optic nerve head (ONH) structural parameters characterized in vivo using spectral domain optical coherence tomography (SD-OCT).
  
  
  METHODS
  Five rhesus macaques were tested under isoflurane anesthesia. SD-OCT images of the ONH of both eyes were acquired 30 minutes after IOP was stabilized to 10 mm Hg and 60 minutes after stabilization to 45 mm Hg. The internal limiting membrane, Bruch's membrane/retinal pigment epithelium, neural canal opening (NCO), and anterior lamina cribrosa surface (ALCS) were delineated using custom software. Differences in SD-OCT structural parameters between the two IOP levels were assessed using generalized estimating equations. In six eyes of three animals, images were acquired after 10 minutes and 30 minutes of IOP stabilization to 10 mm Hg (control experiment).
  
  
  RESULTS
  Acute IOP elevation resulted in a reduction in prelaminar tissue thickness (mean, -47 μm; SD, 25 μm; P = 0.002), rim volume (-0.05 mm(3), 0.02 mm(3); P = 0.002), rim width (-30 μm, 7 μm; P = 0.002), and in an increase in NCO depth (38 μm, 15 μm; P = 0.002). An increase in ALCS depth was significant relative to peripheral Bruch's membrane (48 μm, 24 μm; P = 0.002) but not relative to the NCO. No significant parameter changes were detected in the control eyes.
  
  
  CONCLUSIONS
  Surface compliance changes in the normal monkey ONH primarily reflect prelaminar and peripapillary deformation. SD-OCT compliance testing will further our understanding of the effects of IOP on the ONH and help improve and validate numerical models of ONH biomechanics.
authors: Optic Nerve Head Research Laboratory, Devers Eye Institute, Legacy Health, Portland, Oregon 97208-3950, USA.
authors: Nicholas G
authors: NG
authors: Strouthidis
authors: Brad
authors: B
authors: Fortune
authors: Hongli
authors: H
authors: Yang
authors: Ian A
authors: IA
authors: Sigal
authors: Claude F
authors: CF
authors: Burgoyne
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D018450:Disease Progression; D005500:Follow-Up Studies; D007429:Intraocular Pressure / Q000502:physiology*; D008253:Macaca mulatta; D009798:Ocular Hypertension / Q000150:complications / Q000473:pathology* / Q000503:physiopathology; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D041623:Tomography, Optical Coherence / Q000379:methods*