Videos surfaced on social media after a video showing a snippet of her “malfunction” during the show was circulated.
The clip, which has racked up over 18 million views, shows the singer struggling to open her right eye as she tries to prompt it with her hand.
The mum-of-one sported a silver dress adorned in crushed cans, where Katy can be seen struggling to open her eyelid while staring into the distance.
She then casually turns to look at the crowd and regains composure, before telling fans: “Make even more noise for my band.”
One concerned commenter wrote: “What in the Justin Bieber is going on here?”
Another added: “Is this real? Really worried for her,” while a third chimed in: “Doesn’t matter what caused it. The fact that it happened is scary as hell.”
Some joked Katy had been hit by a “mechanical failure” or a “glitch” in the matrix, with others assuming it was “facial paralysis”.
But Katy’s fanbase later said: “Lol it’s her eyelash glue getting stuck to her bottom lid, happens to me all the time.”
Others suggested the California-born artist takes on the role of a doll-like character as a skit throughout her show, where the doll “tilted back and the eyes close, but one of the eyelids got stuck open”.
During an episode of American Idol last year – where Katy sits on the judge’s panel – she told a contestant she suffers from “wonk eye”.
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