PRK Perfect Vision then Worse Vision Later in the Day?

Blurred vision that gets worse throughout the day while recovering from PRK is almost always due to dry eyes.  That is not surprising given how dry the weather has been this season.  The treatment is to maximize lubrication with artificial tears and to keep hydrated.  In some cases punctal plugs or lubricating ointments are necessary.  Having said that, since you are experiencing new symptoms you should see your surgeon and have him take a look.  Pre-operative selection and planning and post-operative care are the most important part of any surgery