Interesting topic for me, because my vision is indeed awful, and I miss a great deal without glasses. Trying to wear eyeglass frames while deep-throating and sucking balls is a real challenge.
I can wear contacts for distant vision, which helps with the "long" picture, but at anything closer than 5 feet I need reading glasses combined with them, so I'm back to square one. An oddity of my unaided vision, though, is that I have almost magnifying-glass vision at about 4 to 8 inches. So up-close views of his dick & balls are really spectacular, I can see every lovely pore. I just can't see his face at the same time.
So no, I don't wear glasses during sex, which always includes some oral. My partner doesn't need glasses since his eye surgery, so no issue on his part. But had any of my previous lovers wanted to wear glasses (none did) I can't see what objection I would have, if they wanted. Just don't poke me down there with them.