Abstract
Approximately 25% of people report sneezing in response to exposure to bright light (such as direct sunlight) or using light to induce a sneeze when feeling the need to do so. Despite photic sneezing being a widespread phenomenon, which poses some occupational hazards in safety-critical and health-care contexts (e.g. ophthalmological examinations employing bright light), the retinal and neural mechanisms underlying it are not known. In the literature, there are very few studies that have attempted to induce photic sneezing using artificial stimuli, which could be manipulated parametrically to examine and isolate the specific retinal mechanisms underlying this response. Here, we take the first steps at understanding the determinants of photic sneezing, focusing on large scale online surveys to inspire future laboratory experiments. Participants completed self-report two online surveys including questions on iris colour, time spent outdoors, sensitivity to light, chronotype, seasonality, allergies and nasal obstruction (n = 1,854 participants), and about the lighting conditions that elicit a sneeze, time-of-day dependence, and agents other than light eliciting a sneeze (n = 1,943). In addition, a self-report logging study is currently in progress (n = 533). In future work, we will engineer a laboratory-based stimulus to examine which aspects of wavelength and intensity cause photic sneezing to hone in one the underlying retinal mechanisms.
