title: Diurnal variation of retinal thickness in healthy subjects.
abstract: OBJECTIVE
  To investigate diurnal fluctuations in retinal thickness using spectral domain optical coherence tomography (SD-OCT).
  
  
  METHODS
  Spectralis SD-OCT was used to obtain data from the right eye of 21 healthy subjects (mean age, 31.3 years) at 7 AM, 1 PM, and 7 PM. For each eye, a full peripapillary retinal nerve fiber layer circular scan and a 19-line horizontal raster scan (6- by 6-mm area) centered on the fovea were performed.
  
  
  RESULTS
  Retinal nerve fiber layer thickness was greater at 7 AM or 1 PM than at 7 PM for nasal (79.1 μm [1 PM] vs. 77.6 [7 PM]; p = 0.024), inferior (134.1 [7 AM] vs. 131.9 [7 PM]; p = 0.009), and inferonasal (115.2 [7 AM] vs. 115.6 [1 PM] vs. 112.4 [7 PM]; p < 0.001) subfields. Macular thickness was greater at 7 AM than at 7 PM for inferior 6 mm (290.2 μm [7 AM] vs. 287.8 [7 PM]; p < 0.001) ETDRS (Early Treatment Diabetic Retinopathy Study) subfield. Macular volume was greater at 7 AM than at 7 PM for nasal 3 mm (0.541 mm vs. 0.538; p = 0.028) and inferior 6 mm (1.538 vs. 1.525; p < 0.001) ETDRS subfields. The remaining studied areas did not show any significant change throughout the day.
  
  
  CONCLUSIONS
  The Spectralis SD-OCT retinal thickness measurements showed a small but statistically significant diurnal variation in nasal and inferior subfields toward smaller values in the evening. However, the overall change is close to the instrument's resolution and repeatability.
authors.affiliation: *MD Poostchi Ophthalmology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Hossein
authors.initials: H
authors.lastname: Ashraf
authors.forename: Mohammad H
authors.initials: MH
authors.lastname: Nowroozzadeh
mesh_terms: D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology*; D015331:Cohort Studies; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000502:physiology; D009929:Organ Size; D011446:Prospective Studies; D012160:Retina / Q000033:anatomy & histology*; D012165:Retinal Ganglion Cells / Q000502:physiology; D041623:Tomography, Optical Coherence