title: The physiological variation of the retinal nerve fiber layer thickness and macular volume in humans as assessed by spectral domain-optical coherence tomography.
abstract: OBJECTIVE
  With the introduction of spectral domain-optical coherence tomography (SD-OCT), changes in retinal nerve fiber layer (RNFL) thickness and macular volume (MV) can be detected with high precision. The aim of this study was to determine whether there is a physiological quantifiable degree of variation of these structures in humans.
  
  
  METHODS
  This study took place during a 10-km charity run at VU University Medical Center Amsterdam. Weight, height, hydration status, RNFL thickness (ring scan, 12° around the optic nerve head), and MV (20° × 20°) were assessed in 69 subjects (44 runners, 25 controls) using SD-OCT with eye-tracking function. The SD-OCT scans were assessed before running (normal status), after running (more dehydrated status), and 1 to 1.5 hours after finishing the run (rehydrated status). Controls were measured at the same time intervals as the runners but did not participate in the running event. Changes over time were assessed by general linear models, correcting for repeated measurements.
  
  
  RESULTS
  In runners, a significant increase in both RNFL thickness (94.4 μm [baseline] to 95.2 μm [rehydration], P = 0.04) and MV (288.9 μm [baseline] to 291.0 μm [rehydration], P < 0.001) over time was observed. Controls did not show significant changes over time. Anatomically, the physiological change of RNFL thickness was most marked in the nasal sectors.
  
  
  CONCLUSIONS
  This prospective study demonstrated a significant physiological variation of the RNFL thickness and MV at a proportion that, on an individual patient level, may be relevant for longitudinal studies in neurodegenerative diseases.
authors.affiliation: Department of Neurology, MS Center, VU University Medical Center, De Boelelaan 1118, 1081 HZ Amsterdam, The Netherlands. l.balk@vumc.nl
authors.forename: Lisanne J
authors.initials: LJ
authors.lastname: Balk
authors.forename: Judith M
authors.initials: JM
authors.lastname: Sonder
authors.forename: Eva M M
authors.initials: EM
authors.lastname: Strijbis
authors.forename: Jos W R
authors.initials: JW
authors.lastname: Twisk
authors.forename: Joep
authors.initials: J
authors.lastname: Killestein
authors.forename: Bernard M J
authors.initials: BM
authors.lastname: Uitdehaag
authors.forename: Chris H
authors.initials: CH
authors.lastname: Polman
authors.forename: Axel
authors.initials: A
authors.lastname: Petzold
mesh_terms: D000328:Adult; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008266:Macula Lutea / Q000166:cytology*; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000502:physiology*; D011446:Prospective Studies; D012016:Reference Values; D015203:Reproducibility of Results; D012165:Retinal Ganglion Cells / Q000166:cytology* / Q000502:physiology; D041623:Tomography, Optical Coherence / Q000379:methods*; D014792:Visual Acuity