As vast a series as it is, One Piece has plenty of unsolved mysteries that intrigue fans to the point of theorycrafting. Yet none in the New World have been as addictive to fans as theorizing about Zoro’s left eye being closed.
While also being the source of many jokes and memes for the One Piece community, there are some great theories about the eye as well. Some are simply based on real-life principles, while some deal with the more mystical aspects of Zoro’s seen techniques.
Regardless of category, all the predominant theories are well made, thought out, and thoroughly debated by the One Piece community. Yet the following stand out from the crowd, whether for their realisticness, creativity, or just plain awesomeness.
The best theories on the secrets of Zoro's left eye from the One Piece community
The Conquering King, Zoro
One popular fan theory is that Zoro has Conqueror’s Haki, and activates this power via his left eye. While Conqueror’s Haki seems to emanate from a person’s entire body and aura, Oda has emphasized the eyes of the activator when this Haki is used.
This theory is somewhat double layered. One must prove both that Zoro has Conqueror’s Haki and that his left eye is integral to its activation. As stated, Oda does place emphasize the user’s eyes during Conqueror’s Haki activation. That’s half of the theory addressed.
Evidence that Zoro has Conqueror’s Haki is much more plentiful, however. In pre-timeskip One Piece, Zoro is often seen acting like a Captain and is occasionally even mistaken as the Straw Hats Captain.
In the One Piece Punk Hazard arc, fans theorize Zoro uses Conqueror’s Haki against Monet. This is evidenced by her sudden stop of movement and shock, which has been a reaction from unsuspecting individuals in One Piece before.
There’s also a precedent for multiple members of a crew having Conqueror’s Haki. Big Mom and Katakuri both have it, and Big Mom and Kaido were both on the Rocks Pirates crew and possessed Conqueror’s Haki.
Demon Asura Zoro
Another popular One Piece fan theory is that Zoro’s left eye was closed to help maintain control over his Asura powers. The crux of this theory is that Zoro is “possessed” by the Asura demon as a result of his use of cursed swords throughout One Piece.
While Zoro has been shown to use this form in One Piece without opening his eye in post-timeskip, the theory still holds water. Zoro’s left eye has glown multiple times throughout the series, most prominently during the Water 7 saga.
In fact, Zoro not opening his eye could be him successfully controlling the power and surge of the demon Asura, which he couldn’t before. This would explain why the left eye glow only appeared when Zoro got very serious in battle.
Given Mihawk was his master, Zoro could’ve even been instructed by Mihawk to close his eye and not rely on the demon’s power. Mihawk sets high standards for Zoro, and would likely want to make sure Zoro usurps Mihawk with his own strength, not Asura’s.
The real-life concept: Ocular dominance
While not as flashy as the others, the most plausible theory the One Piece community has come up with is that of ocular dominance.
Ocular dominance is a medical phenomenon in which one eye is used more often, has better vision, or can fixate on something better than the other eye. In a profession like swordsman, one certainly benefits from having 20/20 vision or eyes which perform at the same level.
Given Mihawk’s epithet “Hawk Eye,” one would assume the One Piece World’s Greatest Swordsman to be an expert on vision. It’s entirely possible Mihawk noticed through their duel and training that Zoro suffers from ocular dominance in his left eye. That is to say, the left eye is stronger than the right.
As a result, maybe Mihawk scarred the left eye shut and instructed Zoro not to open it until his right eye was trained enough. This theory holds a lot of water, as Zoro has always gotten lost in the series and even misread a signpost in Sabaody.
Oda is certainly known for his foreshadowing and affinity for subtle hints, so this theory also fits Oda’s style of writing for One Piece. Combined with the evidence for this theory, it becomes hard to refute the One Piece community’s realistic explanation for Zoro’s eye being scarred.
While this may seem underwhelming to some One Piece fans, perhaps an alternative perspective could sway them. If Zoro has only been working with one eye so far in One Piece’s New World, imagine what he can do with both open.
Zoro has managed to steal the show every New World arc he’s been a part of, mainly through his combat moments. If he was a show stealer with one open eye, he'd be a show stopper with two. Truly a swordsman worthy of being on the future Pirate King’s crew and inheriting the title of World’s Best.
While all theories presented in this article are plausible, it’s the ocular dominance theory that wins out. The One Piece plot development is a perfect match for this theory, and a plethora of evidence is available to build the theory with.
Despite being less realistic, the Demon Asura and Conqueror’s Haki theories are great as well. Both have enough evidence to be taken seriously while also being the right combination of exciting and logical.
Regardless, these are all just theories in the end, and until Oda decides to show it in One Piece, fans won’t know for sure why Zoro’s left eye is closed. At least speculation is as enjoyable a pastime as there is when it comes to One Piece.