title: Full-field chromatic pupillometry for the assessment of the postillumination pupil response driven by melanopsin-containing retinal ganglion cells.
abstract: OBJECTIVE
  The postillumination pupil response (PIPR) is produced by intrinsically photosensitive retinal ganglion cells (ipRGCs). We aimed to refine the testing conditions for PIPR by investigating whether a greater PIPR can be induced using full-field light stimuli of shorter duration and lower intensity than that produced by existing protocols that use central-field stimuli.
  
  
  METHODS
  Pupil response was recorded with an eye tracker in 10 visually-normal subjects. Red and blue light stimuli were presented using a Ganzfeld system. In Experiment 1 (intensity trials), PIPR was induced using 1-second full-field stimuli of increasing intensities from 0.1 to 400 cd/m(2) (11 steps). For comparison, PIPR also was induced using a 60° × 90° central-field blue stimulus of 400 cd/m(2). In Experiment 2 (duration trials), PIPR was induced using 100 and 400 cd/m(2) full-field stimulus of increasing duration from 4 to 1000 ms (10 steps).
  
  
  RESULTS
  Results indicated that PIPR increased monotonically with increasing stimulus intensity. Full-field stimulation using blue light at 400 cd/m(2) intensity induced significantly more sustained PIPR than central-field stimulation (P = 0.001). In addition, PIPR increased as the stimulus duration increased from 4 to 200 ms; however, no further increase in PIPR was observed when the duration increased from 400 to 1000 ms.
  
  
  CONCLUSIONS
  Compared to existing central-field protocols, larger PIPR can be induced with a full-field stimulus with lower intensity and shorter duration, indicating that PIPR is a function of stimulus intensity, stimulus duration, and retinal area stimulated. The testing protocol can be refined with this new knowledge to target particular clinical populations.
authors.affiliation: Program in Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, Canada.
authors.forename: Shaobo
authors.initials: S
authors.lastname: Lei
authors.affiliation: Program in Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, Canada Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Canada.
authors.forename: Herbert C
authors.initials: HC
authors.lastname: Goltz
authors.affiliation: Program in Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, Canada.
authors.forename: Mano
authors.initials: M
authors.lastname: Chandrakumar
authors.affiliation: Program in Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, Canada.
authors.forename: Agnes M F
authors.initials: AM
authors.lastname: Wong
mesh_terms: D000328:Adult; D003623:Dark Adaptation; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008027:Light; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D011680:Pupil / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000528:radiation effects*; D017299:Rod Opsins / Q000378:metabolism*; D055815:Young Adult; D000099210:Melanopsin
chemical_list: D017299:Rod Opsins; D000099210:Melanopsin
keywords: chromatic pupillometry; intrinsically photosensitive retinal ganglion cells; melanopsin-containing retinal ganglion cells; pupillometry