8.0 vision

“...She looks so happy,” said the rune magician suddenly as he stared six hundred
meters ahead without using his binoculars. “She looks so very, very happy. She always
lives such a happy life.” His sounded like he was spitting out some kind of thick liquid.
“How long do we have to keep ripping that to pieces?”
Kanzaki stared six hundred meters ahead from behind Stiyl.
Even without using binoculars or magic, she could see clearly with her 8.0 vision.
Through the window, she could see the girl angrily biting down on the boy’s head while
he flailed his arms around and struggled.

- Toaru Majutsu no Index Volume 1, Chapter 2 Part 2