This summer my sister and I went to a rock festival in northern Minnesoota. We both noticed an odd occurence after rocking out with Alice Cooper , Sammy Hager and others for four days. Both of us had no trouble reading newsprint without our usual glasses. This only lasted for maybe half a day. Anyone have any idea of what went on ? No mushrooms were involved 
I have absolutely atrocious eyesight—and I’ve seen Alice Cooper at least once each year for the last four years (and again next month), and my eyesight is always still atrocious afterwards. In fact, it’s usually worse because of all the smoke at the concert. (The shows I’ve seen have almost all been indoors)
Well, marijuana is supposed to ease glaucoma, right? Maybe somehow all of the pot smoke you inhaled at the concert (I assume it was there) relaxed your eyes somehow?
Or maybe Alice did his famous song, “No More Mr. Near-sighted”?
WAG: You otherwise would have spent a lot of time in front of a monitor. Your eyes got four days of rest and gentle exercise.
Sorry to resurrect this thread, but I have this to add:
I have noticed a similar effect during times of fatigue and I believe it may be the tiredness, rather than the music itself, that causes it.
When I work (or simply stay awake) for long periods, day after day, I start to notice that colours seem more saturated than normal, contrast is more noticeable and certain details become pin-sharp. I have very much less-than-perfect eyesight, so the effect is never sufficient for me to see well without my glasses.
My (completely uneducated) hypotheses so far:
An increase in blood pressure causes a slight deformation of the eyeball, coincidentally causing better focus. - This could even account for the greater colour saturation, as unfocused colours tend to wash into one another and patches of colour with sharp edges tend to look more saturated overall than soft-edged ones
or
The visual parts of the brain start to behave differently and information from the eyes is not processed (and therefore perceived) in the same way.