Photic sneeze reflex

The photic sneeze reflex (also known as Autosomal Dominant Compelling Helio-Ophthalmic Outburst (ACHOO) syndrome or photoptarmosis, of the combining form from Ancient Greek φῶς, phōs, "light" and πταρμός, ptarmós, "sneeze", colloquially sun sneezing or photosneezia) is an inherited and congenital autosomal dominant reflex condition that causes sneezing in response to numerous stimuli, such as looking at bright lights or periocular (surrounding the eyeball) injection. The condition affects 18–35% of the world's population, but its exact mechanism of action is not well understood. The photic sneeze reflex manifests itself in the form of uncontrollable sneezing in response to a stimulus which would not produce a sneeze in people without the trait. The sneezes generally occur in bursts of 1 to 10 sneezes, followed by a refractory period that can be as long as 24 hours. A photic sneeze results from exposure to a bright light and is the most common manifestation of the photic sneeze reflex. This reflex seems to be caused by a change in light intensity rather than by a specific wavelength of light. A survey conducted by the School of Optometry at the University of Alabama at Birmingham found that 67% of respondents who identified as photic sneezers were female and 94% were Caucasian. The study also found that photic sneezing was significantly more common in people with a deviated nasal septum. Further studies have revealed this mechanism to be inherited. Even less well understood than photic sneezing is sneezing in response to periocular injection, a trait that appears to be inherited in an autosomal dominant fashion. During surgeries in and around the eye, such as corneal transplant surgery, the patient often requires injection of a local anesthetic into the eye. In patients who show the photic sneeze reflex, an injection into the eye, such as that undergone in a retrobulbar or peribulbar block, can often elicit a sneeze from the patient. During these procedures, the patient may be sedated prior to the periocular injection.