The Photic Sneeze Reflex (PSR) is a neuro-ophthalmological phenomenon that causes people to sneeze in response to light. The Autosomal Dominant Compelling Helio-Ophthalmic Outburst syndrome is another name for the PSR. PSR is hypothesized to be produced by a shift in light intensity that begins at the beginning of light exposure and worsens with lacrimation or nasal discomfort.