I was reading about the photic sneeze reflex, and was quite interested in the topic since I am one of the minority of people who are blessed with this genetic trait. I say blessed without a hint of sarcasm because I think that there is definitely a valid Autonomic use for it. My explanation may seem simple compared to the tear-duct theory put forward but here it is…
When you are exposed to bright light you sneeze…
When you sneeze your eyes are forced to close, this means…
Option A: Your body doesn’t want you to damage your inner eye so it makes you close your eyes.
Option B: Sneezing(which is a whole body thing) we already know closes the eye, perhaps it also causes a constricion of the pupil to lessen the light entering the eye, forcing the natural adjustment that would have occured more slowly.
So there you have it, the simple answer. Beleive it or not this is something I have always been aware of in myself and have always wanted to find out more, so if anyone would care to discuss this please let me know.
Douglas Boyle