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Optical Imaging of Human Cone Photoreceptors Directly Following the Capture of Light: e79251

PloS one, 2013-11, Vol.8 (11) [Peer Reviewed Journal]

EISSN: 1932-6203 ;DOI: 10.1371/journal.pone.0079251

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  • Title:
    Optical Imaging of Human Cone Photoreceptors Directly Following the Capture of Light: e79251
  • Author: Bedggood, Phillip ; Metha, Andrew
  • Subjects: Bleaching
  • Is Part Of: PloS one, 2013-11, Vol.8 (11)
  • Description: Capture of light in the photoreceptor outer segment initiates a cascade of chemical events that inhibit neurotransmitter release, ultimately resulting in vision. The massed response of the photoreceptor population can be measured non-invasively by electrical recordings, but responses from individual cells cannot be measured without dissecting the retina. Here we used optical imaging to observe individual human cones in the living eye as they underwent bleaching of photopigment and associated phototransduction. The retina was simultaneously stimulated and observed with high intensity visible light at 1 kHz, using adaptive optics. There was marked variability between individual cones in both photosensitivity and pigment optical density, challenging the conventional assumption that photoreceptors act as identical subunits (coefficient of variation in rate of photoisomerization = 23%). There was also a pronounced inverse correlation between these two parameters (p<10-7); the temporal evolution of image statistics revealed this to be a dynamic relationship, with cone waveguiding efficiency beginning a dramatic increase within 3 ms of light onset. Beginning as early as 2 ms after light onset and including half of cells by ~7 ms, cone intensity showed reversals characteristic of interference phenomena, with greater delays in reversal corresponding to cones with more photopigment (p<10-3). The timing of these changes is argued to best correspond with either the cessation of dark current, or to related events such as changes in intracellular cGMP. Cone intensity also showed fluctuations of high frequency (332 plus or minus 25 Hz) and low amplitude (3.0 plus or minus 0.85%). Other groups have shown similar fluctuations that were directly evoked by light; if this corresponds to the same phenomenon, we propose that the amplitude of fluctuation may be increased by the use of a bright flash followed by a brief pause, to allow recovery of cone circulating current.
  • Language: English
  • Identifier: EISSN: 1932-6203
    DOI: 10.1371/journal.pone.0079251
  • Source: Public Library of Science website
    DOAJ Directory of Open Access Journals
    Geneva Foundation Free Medical Journals at publisher websites
    AUTh Library subscriptions: ProQuest Central
    PubMed Central
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