The mystery surrounding the antagonist Obito Uchiha and his eyesight has left room for interpretation for Naruto fans. The reason for this is that mangaka Masashi Kishimoto has made no effort to explain Obito's vision.
While Kishimoto is responsible for several plot holes in the story, there is a solid reason why Obito never lost his eyesight when fellow Sharingan users like Itachi, Sasuke, and even Kakashi did.
Disclaimer: This article contains spoilers from Naruto.
There is no evidence of Obito's eyesight deteriorating
What is the deal with using Mangekyou Sharingan and failing eyesight?
Mangekyou is the fourth stage of the Sharingan in Naruto. In addition to the Sharingan's conventional abilities, the user acquires advanced techniques such as Susanoo, Tsukuyomi, Amaterasu, and Kamui.
However, the Mangekyou Sharingan is a double-edged sword because it makes its users go blind.
Itachi's vision was already failing while fighting Sasuke before he died, and Sasuke needed Itachi's eye transplant done to restore his own failing vision, resulting in the creation of the Eternal Mangekyou Sharingan.
Even with his cautious usage of the Mangekyou, Kakashi began to go blind in his one Sharingan eye near the end of the series.
Thus, it is pretty well established in Naruto that using the Mangekyou Sharingan results in weakened eyes, and that overuse can lead to blindness.
Did Obito have bad eyesight?
So, while Itachi and Kakashi go partially blind and Sasuke regains his vision via the Eternal Mangekyou Sharingan, the question arises: did Obito have bad eyesight? The answer is that there is no evidence that Obito's eyesight has deteriorated.
Interestingly, Obito only had the regular Mangekyou Sharingan because he never received an implant from a family member that would give him the Eternal Mangekyou Sharingan. Nonetheless, he does not go blind.
How did Obito maintain his eyesight?
It is believed that Obito's eyesight is perfect because of Hashirama's cells in his body.
When a young Kakashi, Obito, and Rin were on a mission, an enemy made a cave collapse on them. Obito saw Kakashi about to be buried beneath the falling rocks and pushed him out of the way, getting stuck in his place instead.
Obito was thought to have died that day, but Madara Uchiha secretly saved him.
Madara and his Zetsu treated Obito's wounds and replaced his damaged half of the body with cells from the God of Shinobi Hashirama.
Hashirama's cells have been used for a variety of purposes throughout the Naruto series, including healing and subduing out-of-control Jinchurikis.
Thus, the presence of Hashirama's cells in Obito's body sustained him and prevented his Sharingan from weakening as it would have otherwise.
Obito has a collection of Sharingans
Another possibility is that Obito replaced his eyes on a regular basis.
Obito aided Itachi in the mass murder of the Uchiha clan and collected many Sharingan eyes from dead members, which he then stored in a laboratory.