title: Nerve fiber layer thinning lags retinal ganglion cell density following crush axonopathy.
abstract: OBJECTIVE
  We investigated the progressive nature of neurodegenerative structural changes following injury to retinal ganglion cell (RGC) axons using quantifiable and noninvasive in vivo imaging techniques.
  
  
  METHODS
  To track degenerative RGC progression in retinas following optic nerve crush (ONC) injury, spectral-domain optical coherence tomography (SD-OCT) was used to quantitate the RGC nerve fiber layer (NFL) density. The RGC soma cell density (RCD) was measured by confocal scanning laser ophthalmoscopy (CSLO). The RCD counts were performed using blood vessels as landmarks to anatomically track defined progressive changes in enhanced yellow fluorescent fusion protein (EYFP)-labeled RGCs.
  
  
  RESULTS
  Following ONC injury, 68% of the observed decrease in RCD measured by CSLO and 54% of the NFL thickness obtained by SD-OCT imaging (N=4 retinas) occurred within the first week. Between days 7 and 14, an additional 22% decrease in RCD was concurrent with a 31% decrease in overall NFL thickness. Finally, between days 14 and 21, an additional 10% decrease in RCD measured in vivo by CSLO and 15% decrease in NFL thickness by SD-OCT was observed.
  
  
  CONCLUSIONS
  Our data suggest that in vivo CSLO imaging of EYFP-RGC expression and SD-OCT measured NFL thickness are fast and reliable methods that longitudinally track neurodegenerative progression following ONC injury. Neurodegenerative changes in NFL thickness measured by SD-OCT imaging have the same overall trajectory as those observed by CSLO for RCD; however, changes in NFL thickness initially lag behind in vivo RGC soma counts with a slower decline in overall measurable change.
authors.affiliation: Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida, United States.
authors.forename: Gustavo C
authors.initials: GC
authors.lastname: Munguba
authors.affiliation: Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida, United States.
authors.forename: Sanja
authors.initials: S
authors.lastname: Galeb
authors.affiliation: Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida, United States.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida, United States.
authors.forename: David C
authors.initials: DC
authors.lastname: Landy
authors.affiliation: Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida, United States.
authors.forename: Daisy
authors.initials: D
authors.lastname: Lam
authors.affiliation: Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida, United States.
authors.forename: Andrew
authors.initials: A
authors.lastname: Camp
authors.affiliation: Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida, United States.
authors.forename: Sinthia
authors.initials: S
authors.lastname: Samad
authors.affiliation: Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida, United States.
authors.forename: Mary L
authors.initials: ML
authors.lastname: Tapia
authors.affiliation: Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida, United States.
authors.forename: Richard K
authors.initials: RK
authors.lastname: Lee
mesh_terms: D000818:Animals; D001369:Axons / Q000473:pathology*; D002452:Cell Count; D004195:Disease Models, Animal; D051379:Mice; D008822:Mice, Transgenic; D009409:Nerve Crush / Q000009:adverse effects; D009898:Optic Disk / Q000473:pathology*; D020221:Optic Nerve Injuries / Q000473:pathology*; D012165:Retinal Ganglion Cells / Q000473:pathology*; D041623:Tomography, Optical Coherence
keywords: glaucoma; neurodegeneration; optical coherence tomography; retinal ganglion cells; scanning laser ophthalmoscopy