title: The association between dark adaptation and macular pigment optical density in healthy subjects.
abstract: OBJECTIVE
  To investigate whether macular pigment optical density (MPOD) is related to dark adaptation in healthy subjects.
  
  
  METHODS
  Dark adaptation was measured after a minimum 30 % pigment bleach in 33 subjects (aged 15-68), using a white 1° stimulus presented 11° below fixation on a cathode ray tube monitor. The luminance range of the monitor was extended using neutral density filters. A heterochromatic flicker photometry based instrument (MPS 9000) was used to measure MPOD.
  
  
  RESULTS
  The average MPOD for the whole group was 0.37 ± 0.21 optical density units. Subjects with lighter irides had on average 40 % lower MPOD compared to those with darker irides (0.3 ± 0.20 vs 0.5 ± 0.19). Group mean MPOD was weakly associated with second (r = 0.32, p = 0.07) and third rod-mediated recovery rates (r = 0.31, p = 0.08) and with the rod threshold (r = -0.24, p = 0.18) 30 min after the onset of bleach. MPOD was unrelated to cone time constant (r = -0.02, p = 0.91), cone threshold (r = -0.01, p = 0.96), rod-cone break (r = 0.13, p = 0.45) or the rod-rod break (r = 0.11, p = 0.52). The second rod-mediated recovery rate (S2) for the lower 10th percentile of MPOD (n = 4) was 0.18 log cd.m(-2).min(-1) and 0.24 log cd.m(-2).min(-1) for the upper 10th percentile (n = 4). The two groups were significantly different (t = -2.67, p = 0.037).
  
  
  CONCLUSIONS
  We report a statistically significant difference between subjects falling in the 10th percentile extremes of MPOD and rod-mediated but not cone-mediated sensitivity recovery. Further investigation into the relationship between MPOD and rod function is warranted, particularly extending the work to encompass those with low MPOD and poor night vision.
authors.affiliation: The Vision Centre, Faculty of Life Sciences, University of Manchester, Carys Bannister Building, Manchester, M13 9PL, UK, laura.patryas@manchester.ac.uk.
authors.forename: Laura
authors.initials: L
authors.lastname: Patryas
authors.forename: Neil R A
authors.initials: NR
authors.lastname: Parry
authors.forename: Dave
authors.initials: D
authors.lastname: Carden
authors.forename: Tariq
authors.initials: T
authors.lastname: Aslam
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Murray
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D003623:Dark Adaptation / Q000502:physiology*; D005127:Eye Color; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D014975:Lutein / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010783:Photometry / Q000379:methods; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology*; D012168:Retinal Pigments / Q000378:metabolism*; D011795:Surveys and Questionnaires; D014792:Visual Acuity; D024341:Xanthophylls / Q000378:metabolism*; D055815:Young Adult; D065146:Zeaxanthins
chemical_list: D012168:Retinal Pigments; D024341:Xanthophylls; D065146:Zeaxanthins; D014975:Lutein