The stiches aren't to keep his sharingan eye forcibly open. As we know, Kishi retconned Izanagi/ Izanami to no longer shut the eye, but strike it blind:
[top right panel here]
As you can see, Itachi relates the consequences of Izanagi and Izanami to be one and the same. Therefore, its only logical to assume that Kishi retconned those techniques to strike eyes blind rather than forcibly close them shut. So unless Kishi retconned the retcon, this guy isn't stapling his eye open due to having used Izanagi/Izanami.
Rather, consider the possibility he's a victim of brainwashing and was forced to watch propaganda orchestrated by a third party. Perhaps someone else, like Orochimaru, pulled this man's strings by brainwashing him to believe Sasuke was the enemy. This is why his eyes are stapled open.
This third party could have convinced the mystery man of a reality that does not actually exist, and instead paints Sasuke as the ultimate villain. This would explain the duo's insatiable desire to harm/ manipulate sasuke and their utter lack of logic. The mystery man would, therefore, be a new character that has somehow gained some control of the Sharrinnegan/ juubi.
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[top right panel here]
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As you can see, Itachi relates the consequences of Izanagi and Izanami to be one and the same. Therefore, its only logical to assume that Kishi retconned those techniques to strike eyes blind rather than forcibly close them shut. So unless Kishi retconned the retcon, this guy isn't stapling his eye open due to having used Izanagi/Izanami.
Rather, consider the possibility he's a victim of brainwashing and was forced to watch propaganda orchestrated by a third party. Perhaps someone else, like Orochimaru, pulled this man's strings by brainwashing him to believe Sasuke was the enemy. This is why his eyes are stapled open.
This third party could have convinced the mystery man of a reality that does not actually exist, and instead paints Sasuke as the ultimate villain. This would explain the duo's insatiable desire to harm/ manipulate sasuke and their utter lack of logic. The mystery man would, therefore, be a new character that has somehow gained some control of the Sharrinnegan/ juubi.