Rapid increase in blood movement... basically what xxorama said.
Changes in blood pressure maybe?
Medication is a tricky thing I know my vision fluctuates with my blood pressure fluctuates with blood pressure as I medicate. I would look up the listed and known side effects for his Meds, and see if vision effects are one the list. Also I am not a Doctor, I would talk to his doctor or a different one about the medication. Sometimes medication can work together in combo and produce side effects. The dirty little secret is every time one starts a medication it is an experiment as far as side effects and effectiveness, everyone is different enough that no Meds behave the same in ones body.
you should go to the eye doctor and have a check up...doesn't sound normal to me
YOU ARE GOING THROUGH WHAT IS CALLED THE AWAKENING LOOK IT UP IT WILL TELL YOU ALL ABOUT IT OK