They lived to see their dreams. And when they slept, they dreamed about their dreams. It is not the act seeing itself that is harmful for the characters in this film. It is the act of seeing through mediums. It might be interesting to consider that images are not what we see.
Images are a creation.
A mediated version of what has existed in light somewhere. What we see is something else. Something felt more than seen. Included with the Japanese import laserdisc version of Until the End of the World is an hour long documentary-esque film by Sean Naughton called Dream Island . Images captured, as I've said before, are already mediated.