It's good you included your location.
In the US, opticians have to provide your script whether you ask for it or not.
I didn't find something as official for Canada with a 5-second web search, but this Ontario College FAQ indicates Canada has something similar.
PD is annoying, for sure. But the FTC website I linked above covers that too:
"Oh, you don't share prescriptions with the patient? I thought that was an FTC regulation. Here, let me pull that up on my phone right quick to clarify. Pretty sure they even have an email contact I can reach out to if needed."
Knowledge is half the battle. Have the info to back yourself, then hold your ground. Scummy optometrists rely on people not knowing their consumer rights.