One of the most striking and debated physical traits that define his character in the One Piece series is the eye scar of Roronoa Zoro. First crossing over his left eye, this mark made its appearance after the two-year skip in the series and has since held huge interest for fans, with much speculation into how he got it and what it all means.
The scar was revealed when Zoro returned to Sabaody Archipelago after his two-year training with Dracule Mihawk. This timing clearly associates the scar with Zoro's extreme training regime by declaring it as an injury he had incurred during this most critical period of his development as a swordsman.
It's significant to note that whereas some sources refer to the scar as being on Zoro's right eye, it is actually on his left eye. This detail gives relevant proof of having correct accounts on the said character. Much speculation about whether Zoro can still see out of his left eye or not has been sparked by the nature and location of the scar. This aspect was never confirmed or denied in the series.
The mystery of Zoro's eye scar becomes deep, especially as neither he nor any of his fellow crewmates have ever directly mentioned or questioned the source of the scar within the story. Therefore, it has left fans wondering and speculating, since in the actual story itself, there is no mention of what happened; with time, it has evolved into one of the most discussed features of Zoro's post-skip appearance.
While Eiichiro Oda of One Piece has really kept quiet about Zoro's eye scar, he has mentioned that there is more to it than meets the eye. This is what confirms that the reveal had been planned since a while back and will either have meaning for Zoro's character development or materialize in future storylines.
It is not merely the look of the scar, but a very big point in Zoro's path to become a swordsman of the world's greatest nature. Comparisons between Zoro's and that of Rayleigh, blind on the side over his right eye, yet he seems to see everything with that eye, have been brought out by fans. This has created much speculation about their paths or abilities having similarities.
Zoro's eye scar is one of the many he has accrued from questing experience, symbolizing important events within his journey. At the same time, this particular scar above the eye appears to be the most prominent, with mystery hovering over its originating factor. Whereas others like the one across his chest, from his first encounter with Mihawk, are accounted for, the same cannot be said about the scar above his eye.
The presence of the scar has also led to much debate about its potential impact on Zoro's fighting style and abilities. Some fans have speculated that maybe it conceals a secret technique or power, though no concrete evidence has been given through the series to support these theories.
Character design with the addition of the eye scar is for visual representation of Zoro's growth and trials during timeskip. This gives him even more ruggedness in appearance, really coming out to convey the battle-hardened, superior-quality swordsman image—through intense training and strong opponents.
One of the many unanswered questions of the series is Zoro's eye scar. Many are waiting for the day it is revealed what happened to him. The scar will always be there throughout the series as a subtle reminder of what has been going on outside of view with Zoro during his training period, showing him as a more rounded character with room for future revelations.