Originally Posted by Vilya
Yeah, that would be the result of internalizing the energies from his eyes. What happens is she got so caught up in those great lookin blue eyes for the first time that she loses concentration and POW*
It's pretty much established that Jean's never seen Scott's eyes before and Scott's never seen Jean on his own. There's a back cute story about shortly after they met, where a blindfolded Scott was able to show Jean his eyes by thinking a picture of them to her telepathically, and Jean was able to show him what she looked like the same way. To see each other eye to eye with nothing in between, it is pretty touching, isn't it? And then losing each other in the moment, it certainly would be a good reason to get distracted and forget about those force fields you're trying to maintain over his eyes.
That final moment where Jean suddenly opens her eyes in concern could be either a sign that the evil inside is waking up, or perhaps "OMG! I forgot about those optic blast forcefields!"