Kramer goes to an optometrist and he's lead into a room where the doctor pulls down a small screen with letters. "Read me the bottom line, Mr. Kramer."
"Sorry, Doc, I can't."
"Okay, how about the line above that?"
"The next one up?"
This goes on for half an hour with the optometrist pulling down progressively larger and larger eye charts with ever bigger letters Finally, the doctor says, 'Well, I've never had to use it before, but see if you can read this."
With that, he pulled a lever, the wall collapsed and a giant 50 foot flaming orange 'A" rose up out of the ground.
'Now surely you can read THAT!" snarled the frustrated optometrist."Sorry, Doc, but I can't." "Then, man, you must be blind!" "Oh no, Doc, my eyesight's fine. I just never learned how to read!"