title: Dark adaptation in relation to choroidal thickness in healthy young subjects: a cross-sectional, observational study.
abstract: BACKGROUND
  Dark adaptation is an energy-requiring process in the outer retina nourished by the profusely perfused choroid. We hypothesized that variations in choroidal thickness might affect the rate of dark adaptation.
  
  
  METHODS
  Cross-sectional, observational study of 42 healthy university students (mean age 25 ± 2.0 years, 29 % men) who were examined using an abbreviated automated dark adaptometry protocol with a 2° diameter stimulus centered 5° above the point of fixation. The early, linear part of the rod-mediated dark adaptation curve was analyzed to extract the time required to reach a sensitivity of 5.0 × 10(-3) cd/m2 (time to rod intercept) and the slope (rod adaptation rate). The choroid was imaged using enhanced-depth imaging spectral-domain optical coherence tomography (EDI-OCT).
  
  
  RESULTS
  The time to the rod intercept was 7.3 ± 0.94 (range 5.1 - 10.2) min. Choroidal thickness 2.5° above the fovea was 348 ± 104 (range 153-534) μm. There was no significant correlation between any of the two measures of rod-mediated dark adaptation and choroidal thickness (time to rod intercept versus choroidal thickness 0.072 (CI95 -0.23 to 0.38) min/100 μm, P = 0.64, adjusted for age and sex). There was no association between the time-to-rod-intercept or the dark adaptation rate and axial length, refraction, gender or age.
  
  
  CONCLUSIONS
  Choroidal thickness, refraction and ocular axial length had no detectable effect on rod-mediated dark adaptation in healthy young subjects. Our results do not support that variations in dark adaptation can be attributed to variations in choroidal thickness.
authors.affiliation: Department of Ophthalmology, Zealand University Hospital, Sygehusvej 10, DK-4000, Roskilde, Denmark. icm@dadlnet.dk.|Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200, København N, Denmark. icm@dadlnet.dk.
authors.forename: Inger Christine
authors.identifier: http://orcid.org/0000-0002-0515-5736
authors.initials: IC
authors.lastname: Munch
authors.affiliation: Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200, København N, Denmark.
authors.forename: Cigdem
authors.initials: C
authors.lastname: Altuntas
authors.affiliation: Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200, København N, Denmark.|Department of Ophthalmology, Rigshospitalet, Nordre Ringvej 57, DK-2600, Glostrup, Denmark.
authors.forename: Xiao Qiang
authors.initials: XQ
authors.lastname: Li
authors.affiliation: MacuLogix, 1801 Oberlin Road, Middletown, PA, 17057, USA.
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Jackson
authors.affiliation: Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200, København N, Denmark.|Department of Ophthalmology, Rigshospitalet, Nordre Ringvej 57, DK-2600, Glostrup, Denmark.
authors.forename: Oliver Niels
authors.initials: ON
authors.lastname: Klefter
authors.affiliation: Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200, København N, Denmark.|Department of Ophthalmology, Rigshospitalet, Nordre Ringvej 57, DK-2600, Glostrup, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Larsen
mesh_terms: D000328:Adult; D000367:Age Factors; D058452:Axial Length, Eye / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002829:Choroid / Q000033:anatomy & histology*; D003430:Cross-Sectional Studies; D003623:Dark Adaptation / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D012029:Refraction, Ocular / Q000502:physiology; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology; D012684:Sensory Thresholds / Q000502:physiology; D012737:Sex Factors; D013997:Time Factors; D041623:Tomography, Optical Coherence / Q000379:methods; D014792:Visual Acuity; D055815:Young Adult
keywords: Choroidal thickness; EDI-OCT; dark adaptation; enhanced-depth optical coherence tomography; time-to-rod-intercept