User blog comment:Haki73/Zoros eye?/@comment-216.49.146.175-20110318072013

Basically, he went on a mission with his team, and while his leader (Mihawk) wasn't there, they got ambushed by the Earth Pirates and his teammate, who's name was Obi D. Ochiha, was crushed under a bunch of rocks. Zoro's eye was injured by the Earth Pirates, and Perona used her Devil Fruit powers to take Obi's eye and implant it into Zoro's, now giving Zoro the power to see like a D.

Get it, C like a D?