I would like to see reliable documentation of this. I've heard flash during the *development* of the eye is not good (such as through the thin eyelids of a young animal), but not that it's bad on a fully functioning, normal eye. Eyes are made to receive light, and I don't see any reason at all that flash shouldn't be used other than the "stress factor". Of course, if I saw anything with actual research done I'd be willing to change my mind. JMO.I've read in multiple different places that using flash isn't such a good idea while taking pictures of animals as it hurts their eyes and can even cause seizures in rare cases, I would imagine it would only be worse for nocturnal animals whose eyes are very sensitive to light. Maybe you could just try to capture them in the brightest possible ambient light instead? I never use flash in my pics (just in case) and most come out just fine. Better safe than sorry, just my two copper.