The "claim" is that you can be driving NEXT DAY...... obviously its all dependent on each individual..... and in most cases it IS TRUE...
For me however it was the day after next simply because of the size and shape of my flap that was cut it had to have its "hinge" at the nasal aspect rather than at the top.... so to stop gravity affecting the flap and the risk of it possibly sliding down and becoming misaligned i had a non prescription 'bandage' contact lens applied over my flap....
This made my vision 'soggy' because the water / fluds that were on my eye during the surgery had been trapped under it - so protein had built up in the hours after surgery making me feel like i had scum in my eyes!!
However when the contact lens was removed i rinsed my eyes with the drops given post op and my vision was near perfect!
I think the "fluctuations" you mean would have to be a PHYSICAL change in prescription "right in front of your eyes" kind of thing..... this wont happen...
My Astigmatism immediately post op was still 1.50 dioptres - bear in mind there may be oedema (water swelling) in the area causing the front of the eye not to be perfectly in the right place.... over the following week this must have settled as my astigmatism came down to 0.50.
(I only had a residual in my RIGHT eye. MY left eye was totally non prescription therefore the 1.50 diopter astigmatism in the right eye was not noticed as the left eye 'took over' and sort of cancelled out the blurring) so over the weeks of "settling" there were no visible fluctuations)
Now when its tested its usually in the range of 0.25-0.50.... this ISNT a fluctuation but merely a tolerance level between tests.. For example if you had 3 eye tests in 1 hour EVERY single on would have slight variations.
Hope this helps
JONATHAN