title: Longitudinal change detected by spectral domain optical coherence tomography in the optic nerve head and peripapillary retina in experimental glaucoma.
abstract: OBJECTIVE
  To investigate whether longitudinal changes deep within the optic nerve head (ONH) are detectable by spectral domain optical coherence tomography (SDOCT) in experimental glaucoma (EG) and whether these changes are detectable at the onset of Heidelberg Retina Tomography (HRT; Heidelberg Engineering, Heidelberg, Germany)-defined surface topography depression.
  
  
  METHODS
  Longitudinal SDOCT imaging (Spectralis; Heidelberg Engineering) was performed in both eyes of nine rhesus macaques every 1 to 3 weeks. One eye of each underwent trabecular laser-induced IOP elevation. Four masked operators delineated internal limiting membrane (ILM), retinal nerve fiber layer (RNFL), Bruch's membrane/retinal pigment epithelium (BM/RPE), neural canal opening (NCO), and anterior lamina cribrosa surface (ALCS) by using custom software. Longitudinal changes were assessed and compared between the EG and control (nonlasered) eyes at the onset of HRT-detected surface depression (follow-up 1; [FU1]) and at the most recent image (follow-up 2; [FU2]).
  
  
  RESULTS
  Mean IOP in EG eyes was 7.1 to 24.6 mm Hg at FU1 and 13.5 to 31.9 mm Hg at FU2. In control eyes, the mean IOP was 7.2 to 12.6 mm Hg (FU1) and 8.9 to 16.0 mm Hg (FU2). At FU1, neuroretinal rim decreased and ALCS depth increased significantly (paired t-test, P < 0.01); no change in RNFL thickness was detected. At FU2, however, significant prelaminar tissue thinning, posterior displacement of NCO, and RNFL thinning were observed.
  
  
  CONCLUSIONS
  Longitudinal SDOCT imaging can detect deep ONH changes in EG eyes, the earliest of which are present at the onset of HRT-detected ONH surface height depression. These parameters represent realistic targets for SDOCT detection of glaucomatous progression in human subjects.
authors.affiliation: Optic Nerve Head Research Laboratory, Devers Eye Institute, Legacy Health System, Portland, OR 97208-3950, USA.
authors.forename: Nicholas G
authors.initials: NG
authors.lastname: Strouthidis
authors.forename: Brad
authors.initials: B
authors.lastname: Fortune
authors.forename: Hongli
authors.initials: H
authors.lastname: Yang
authors.forename: Ian A
authors.initials: IA
authors.lastname: Sigal
authors.forename: Claude F
authors.initials: CF
authors.lastname: Burgoyne
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D005901:Glaucoma / Q000175:diagnosis*; D007429:Intraocular Pressure; D008137:Longitudinal Studies; D008253:Macaca mulatta; D008297:Male; D009412:Nerve Fibers / Q000473:pathology*; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D012165:Retinal Ganglion Cells / Q000473:pathology*; D041623:Tomography, Optical Coherence; D014065:Tonometry, Ocular