The Uchiha clan is renowned and feared for their dojutsu, the Sharingan. These special eyes give the user superior eyesight, visual prowess and a whole host of special abilities. The Sharingan and all of its forms have made the Uchiha clan some of the most powerful ninjas in the world. This remains true in Boruto. Since the clan is known for their amazing eyes, it's strange that the newest addition to the clan, Sarada Uchiha, needs glasses to see.
Sarada is the only known Uchiha who has ever needed glasses. This anomaly raises a number of questions about the Sharingan and Sarada herself. The running joke in the fandom is that her mother's genes are so weak that they ruined the Sharingan, but that’s far from the truth. Sarada has inherited Sakura's monster strength and near-perfect chakra control which have all made her a stronger ninja. The actual reason for Sarada's need for glasses is far more interesting.
Sickness Affected Her Eyesight
Sarada has required glasses to correct her eyesight since she was a small child. When she was very young, Sarada grew ill and developed a high fever. While she was sick, Sasuke was gone on his mission to collect information on the Otsutsuki clan. This left Sakura to take care of Sarada by herself. Sarada eventually recovered from the illness, but it left lasting effects.
The fever that Sarada developed seemed to have damaged her eyesight. Karin sent Sarada a pair of glasses to correct her vision, which had become blurred. For years, Sarada wore these glasses. However, they eventually caused trouble when Sarada saw a picture of Karin standing next to Sasuke and thought the woman was her mother because of their similar set of glasses.
This conflict was eventually cleared up with it being confirmed that Sarada is Sakura's daughter. Sarada and Karin have developed a close relationship since then, and Sarada views Karin as a kind of godmother or aunt. Karin often checks up on Sarada and makes sure she is taken care of. Sarada's glasses act as a symbol of the bond between her and Karin.
The Sharingan Doesn't Fix Eyesight
Even after Sarada unlocked her Sharingan, she still required glasses to fix her vision. This is because the Sharingan doesn't improve eyesight unless it's activated. While inactive, a person with a Sharingan will have a normal level of vision, which for Sarada means the damaged vision she has had since childhood.
The Sharingan can actually even damage the user's vision if it's overused, as the Mangekyo Sharingan will gradually deteriorate the user's eyesight each time it's used. Itachi and Sasuke both went nearly blind from overusing their eyes. The Sharingan is therefore a double-edged sword that can hurt one's vision just as much as it can improve it.
If Sarada could maintain having her Sharingan active constantly, she wouldn't need her glasses. She wouldn't only have perfect vision but superhuman eyesight as well. The Sharingan can see chakra as color and view objects on a microscopic scale. The issue with this is that the Sharingan is very draining for her, so she can only maintain it for a short period of time.
Sarada's Glasses Separate Her From Her Parents
From a design standpoint, Sarada's glasses are a great addition to her character. Like many of the other children of the next generation, Sarada's design is a combination of her parents. She physically looks very similar to Sasuke and her clothing is an interesting merging of Sakura and Sasuke's outfits when they were kids. These similarities show the connection she has with her linage and makes her a perfect representative of the Uchiha clan.
One of the major criticisms of Boruto is that many of the characters simply feel like carbon copies of their parents. The glasses prevent Sarada from looking like a clone of her parents. They give her design a sense of independence from both Sasuke and Sakura. Sarada Uchiha is a unique person, different from her parents or any other member of the Uchiha clan.
