title: Variability in bleach kinetics and amount of photopigment between individual foveal cones.
abstract: OBJECTIVE
  To study the bleaching dynamics of individual foveal cone photoreceptors using an adaptive optics ophthalmoscope.
  
  
  METHODS
  After dark adaptation, cones were progressively bleached and imaged by a series of flashes of 545-nm to 570-nm light at 12 Hz. Intensity measurements were made within the foveal avascular zone (FAZ) to avoid confounding signals from the inner retinal blood supply. Over 1300 cones in this region were identified and tracked through the imaging sequences. A single subject was used who demonstrated the necessary steady fixation, wide FAZ, and resolvability of cones close to the foveal center.
  
  
  RESULTS
  The mean intensity of all cones was well-described by first-order kinetics. Individual cones showed marked differences from the mean, both in rate of bleach and amount of photopigment; there was an inverse correlation between these two parameters. A subset of the cones showed large oscillations in intensity consistent with interference from light scattered within the cone outer segment. These cones also bleached more quickly, implying that rapid bleaching induces greater amounts of scatter.
  
  
  CONCLUSIONS
  Neighboring cones in the fovea display high variability in their optical properties.
authors.affiliation: Department of Optometry and Vision Sciences, University of Melbourne, Australia. pabedg@unimelb.edu.au
authors.forename: Phillip
authors.initials: P
authors.lastname: Bedggood
authors.forename: Andrew
authors.initials: A
authors.lastname: Metha
mesh_terms: D005584:Fovea Centralis / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008027:Light; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D012168:Retinal Pigments / Q000378:metabolism; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology*
chemical_list: D012168:Retinal Pigments