[Unknown to Castiel, his vessel, Jimmy Novak, didn't have good eyesight. Requiring glasses for everyday things.]

[And as Jimmy had passed on and Castiel keeping his vessel, the bad eyesight stayed behind.]

[Castiel really didn't know why his eyesight from his vessel was so bad, he assumed humans eyesight wasn't that good unlike an angels. So he never really mentioned it. Though it would irritate him sometimes when he tried reading a lore book or trying to spot something from far away, only to be met with a blurry jumble of words or colors. He was always squinting his eyes to try and see whatever he was looking at better to no avail. It frustrated him as time went on.]

[It was one of those days where Castiel was sat in the library of the bunker, trying to read a lore book he had. All he was doing was squinting his eyes, trying to read the book. It was frustrating him.]