I have been in the waiting room for awhile to wait until the dilation takes effect, then had the exam that the dilation is for. After that it already starting to let go and I have just handled the paperwork about the bill and setting any next appointment. They have given me plastic sunglasses the fit behind the lenses of my glasses and rest on the arms of the glasses that go to your ears. Most of the time I have not needed that as I have my own sunglasses along.
Also, it depends on why you are having an exam if they even dilate your pupils. If you are just there to check refraction for new lenses and not to check for other conditions they are not likely to dilate.