A joke I made up that’s funny only when you look back at it.

This guy shows up to his optometrist and says "I have a weird problem",

The Optometrists replies, "What seems to be the trouble?"

The guys says, "Everything's blurry. My vision is horrible!"

"That's pretty common", the Optometrist replies. "We can certainly fix th…"

"Wait! Here's the weird thing though" the guy interrupts, "Everything is blurry. EVERYTHING. Except… People's butts. People's butts, dogs butts, cats butts. Butts! I see butts clearly! What's going on?"

The Optometrist smiles and calmly replies, "Listen, you've got nothing to worry about. Everyone knows that hindsight is 20/20."