I ordered a pair of polarised sunglasses from Zenni, using my usual prescription. Arrived in a week, look great.
Wore them for driving first time and, bloody hell, rainbows in the sky, and on the road in front. WTF I said to myself. Stopped and looked at the sky from outside the car = no rainbows. The glasses were interacting with the film on the windscreen. Chatted with Zenni, saying that it was distracting from my driving. Full refund minus $10 postage.