Board Thread:Legitimate Canon Questions/@comment-11489125-20141102115433/@comment-4091815-20141102153307

It certainly mimics the "eyeshine" seen in dogs, cats, horses, etcetera but we have no canonical, physiological explanation provided by the show.

The "controlling the eyes during flash photography" thing came from Jeff to explain the Derek's fake driver's license in Season 1.

We have since seen various werewolves make their eyes flash whenever they want suggesting it is a part of their transformation that is controllable.