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Brightness perception changes related to pupil size.

Unni Sulutvedt1, Daniele Zavagno2, Jamie Lubell1

  • 1Department of Psychology, University of Oslo, Oslo, Norway.

Vision Research
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Summary

Pupil dilation, using Tropicamide, significantly enhances the perceived brightness of objects. Larger pupil size leads to a stronger sense of brightness, impacting visual perception.

Keywords:
BrightnessPupillometryTropicamideVisual perception

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Area of Science:

  • Visual Perception
  • Ophthalmology
  • Psychophysics

Background:

  • Pupil size influences the amount of light reaching the retina.
  • The direct causal effect of pupil dilation on perceived brightness is not well understood.

Purpose of the Study:

  • To investigate the causal relationship between pupil size and the subjective perception of brightness.
  • To quantify the impact of pharmacological pupil dilation on brightness perception.

Main Methods:

  • A psychophysical brightness adjustment and matching procedure was employed.
  • Participants (n=30) viewed patterns with one eye treated with Tropicamide to dilate the pupil, while the other served as a control.
  • Subjective brightness of a target pattern was adjusted by participants under different pupil conditions.

Main Results:

  • Pupil dilation with Tropicamide significantly increased the perceived brightness of the target pattern.
  • A dose-dependent relationship was observed, with larger pupil diameters correlating with higher brightness adjustments.
  • An average increase of 2.09 cd/m² in perceived brightness was noted for each 1 mm increase in pupil diameter.

Conclusions:

  • Pupil dilation directly enhances the perceptual experience of brightness.
  • Even minor changes in pupil size can lead to significant alterations in visual perception.
  • Findings have implications for understanding visual processing and potential applications in visual aids.