Few years ago, when I was in high school, I had a classmate who was wearing this really thick glasses. His vision was terrible. But every time he was passing the vision test, he scored the most points. I was wondering how he was doing it, since he could see practically nothing.
The trick was simple.
Back than vision tests were done using Sivcev’s tables. The most common Sivcev table is a poster with rows of random latters. The top row has two letters in biggest font. Next row has three letters in smaller font, and so on. Reading letters from a certain distance can suggest how good a person can see.
The guy just had the whole table memorized. Yes, that’s true. He knew all the letters in all the rows and could spell of them back and forward and as you wish. I thought it was close to impossible at the time.