When Dean Winchester sees sunlight for the first time in forty years, he can't see.
When he first wakes up, he's completely blind. There is only a complete, heavy darkness surrounding him. No light pierces through the darkness of... his coffin, he realizes. He panics briefly, but it's not like he hasn't been in stranger situations. He breaks through the thin wood, of course it's flimsy and fragile. He can't imagine Sam having enough money for anything fancy. He wonders why Sam even chose to bury him; standard hunter protocol is cremation, like they did for Dad.
When he breaks through the lid, dirt tumbles in. He frantically claws his way out, not in a hurry to go back to being dead. His hand reaches the outside first. A cool breeze plays across his skin. His head pops out of the ground, a strange sight that would most likely send people running and screaming. If there had been anybody around.
The light is blinding, too. His first breath of air is a relief; his first gulp of water is bliss, but the light- it hurts. He has to shield his eyes until the multi-colored spots dancing in his vision fade.
It isn't until later that he realizes the light can be just as blinding as the dark.
So when the angels and the demons come looking for him and Sam, he knows his answer.
No.
He's out of the dark, he's out of the light.
He's not blind anymore.
(He can finally see.)