Many years ago, I had just had my first gloucoma eye exam.
Not being able to see very much at all, I walked back to work, and was happily taking phone calls from dealers for spare parts and advice, when the sales director rung. He was desperate for a batch of BBIIGG power amplifier repairs to go out that night.
I explained to him about my eye test, and that I could not see very much. Well, just work by touch he said. It took some time to convince him that probing around with your fingers in a unit that can provide around 400V is not a particularly safe method of working.