title: Physiological variation of retinal layer thickness is not caused by hydration: a randomised trial.
abstract: There is evidence for physiological variation of retinal thicknesses as determined by optical coherence tomography (OCT). We tested if such changes could be explained by hydration and would exceed what may be expected from normal ageing. Subjects (n=26) of a previous study were re-assessed and were randomised to 3 groups of a hydration escalation trial (no hydration, 1× hydration, 2× hydration). Automated retinal layer segmentations were performed for the macular retinal nerve fibre layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL) and outer nuclear layer (ONL). The averaged volumes were calculated for the central foveola, 3 mm and 6 mm circles of the ETDRS grid. Following oral hydration there were no significant differences of retinal layer thicknesses between the three randomised groups in any of the ETDRS regions at any time-point. Ageing related changes were significant over an 18 month period for the GCL. The negative outcome of this trial implies that, until the causes for the observed variation are resolved, investigators may need to accept, and include into trial power calculations, a small degree of variation (<1%) of quantitative SD-OCT imaging either due to human physiology or instrument/software related factors.
authors.affiliation: Department of Neurology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Lisanne J
authors.initials: LJ
authors.lastname: Balk
authors.affiliation: NeuroCure Clinical Research Center, Charité University Medicine Berlin, Berlin, Germany.
authors.forename: Timm
authors.initials: T
authors.lastname: Oberwahrenbrock
authors.affiliation: Department of Neurology, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Bernard M J
authors.initials: BM
authors.lastname: Uitdehaag
authors.affiliation: Department of Neurology, VU University Medical Center, Amsterdam, The Netherlands; UCL Institute of Neurology, Department of Molecular Neuroscience, Queen Square, London, United Kingdom. Electronic address: a.petzold@vumc.nl.
authors.forename: Axel
authors.initials: A
authors.lastname: Petzold
mesh_terms: D000328:Adult; D000367:Age Factors; D000465:Algorithms; D001330:Electronic Data Processing; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007552:Isotonic Solutions / Q000009:adverse effects; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology*; D015588:Observer Variation; D012160:Retina / Q000033:anatomy & histology*; D041623:Tomography, Optical Coherence
chemical_list: D007552:Isotonic Solutions
keywords: Neurodegeneration; OCT; Outcome study; Physiological variation; Secondary outcome marker