This weak point of the Sharingan renders it completely useless.
Naruto has presented over the years various clans with extremely amazing abilities that made them stand out in the Shinobi world, as some of these had techniques worthy of admiration and respect.
One of these clans that is undoubtedly the most popular and powerful is the uchiha clanwhose members have a powerful eye technique called Sharingan that is inherited from generation to generation. This ability gives its wielders incredible illusionary abilities with which they can easily catch their enemies just by looking at them, being almost unbeatable with this power that has few ways to counter it.
However, recently, it has been shown real sharingan weakness. Next, we tell you the details.
This post contains spoilers for Chapter #2 of the Naruto manga: Sasuke Retsuden.
The true weakness of the Sharingan has been revealed

The Sharingan has a real weakness that causes it to be easily countered.
The Sharingan has been one of the most powerful and remarkable ocular jutsus What does this series have? The bearers of this ability are feared and respected throughout the Shinobi world, as it is well known that the Uchiha clan has transcended through the centuries thanks to the exploits of its founder, Madara Uchiha.
This legendary eye jutsu seemed to have few ways to counter itbecause there were few ninjas who dared to challenge a bearer of these eyes, since it was extremely difficult for them to keep up with them in combat.
However, recently it has been discovered real weakness of the Sharingan, something that has taken Sasuke Uchiha himself by surprise.
In the Chapter #2 of the Naruto manga: Sasuke Retsudenit has been observed that Sasuke is still incognito in prison of Redaku waiting to get some kind of relevant information that will lead him to find the cure for the disease that afflicts Naruto.
During this chapter, Sasuke decides to leave his cell to research what happens in this place, because it seems quite strange to him that the leader of this prison has a dinosaur as a pet to guard the inmates. The young Uchiha goes through the corridors of this site analyzing the situation and wondering if this prehistoric creature is part of a summoning technique.
In the middle of the road, Sasuke comes face to face with this dinosaur named Meno, who quickly launches himself at the Shinobi, so the ninja of the leaf decides to use his Sharingan to neutralize this creature through a genjutsu. However, he does not get the expected results, since he is apparently immune to the Uchiha’s eye technique.

Sasuke, using his Sharingan to neutralize Meno through a genjutsu, realizes that Meno is immune.
In view of this, Sasuke decides to use a Kunai to fight this dinosaur, cutting off his limbs in order to neutralize it, since his Sharingan had no effect on it.
The next day, after having had this meeting, Sasuke is in the prison dining room and curiously something catches his attention and he decides to look out the window, surprised to see Meno with all his limbs and without any injuries. This situation restless much to the young Uchiha, because he still does not understand what has happened.
While Sasuke was in shock analyzing the situation, Zansul, the leader of the prison approaches him from behind, so the Uchiha tries to use his Sharingan on him in order to get information about Meno and everything that is happening in this place.
However, the Sharingan genjutsu also has no effect on Zansul, who quickly proves to Sasuke that has glass eyes with which he can easily counteract this ability, as these act as a barrier between the technique and his brain, this being the real weakness of this eye jutsu.

Zansul is immune to the Sharingan genjutsu, as he has glass eyes that allow him to counteract this technique.
This revelation would explain why the Sharingan genjutsu was not effective in Meno, since it is presumed that her eyes could be the same as Zansul.
This chapter has generated a hype in the fans who find willing for knowing more about Zansul and his glass eyes, since they could be part of a new eye technique hereditary similar to the Uchiha clan or just an experiment done in this prison.
It remains to wait for the plot to continue to develop. get to know deeply about Zansul, his dinosaur Meno and why they have those glass eyes.