I figure if a person had never experienced darkens before darkness blindness would be a rather terrifying prospect.
so if a creature with darkvission suddenly found themselves in supernatural darkness (as from a deeper darkness spell cast in a dim room) would you consider that to have some kind of secondary panic effect on them?
totally for RP reasons of course.
The rules are the rules. There is no listed "secondary effect", so there isn't one.
If they want to RP being panicked, they can RP being panicked. Doesn't make much sense as a rule, though. I mean, it would only have an effect the first time you encountered the spell, if at all; in the future you'd go "Oh. Somebody Cast Deeper Darkness."
Depending on the person (or creature) I think panicked, frightened, or shaken might be appropriate. I might even use a will save to downgrade to a milder condition.
Just remember that a lot of creatures with darkvision also sleep and have eyelids.
You seriously need to quit making such good posts. :P
making the rest of us look bad!-S