The 22-year-old can no longer tolerate wearing contact lenses and therefore requires surgery to correct his myopia.
Mancini revealed the Italian striker will go under the knife next week and consequently isn't ready to feature in City's match against QPR this weekend.
"Mario is not ready to return to the pitch yet. He no longer seems to tolerate contact lenses. He's feeling alright now, but the problem can return any time," Mancini told reporters.
|20/1||Manchester City are 20/1 with Paddy Power to beat QPR 3-2 on Saturday|
The City manager is already without key forward Sergio Aguero for the next couple of weeks after he picked up a knee injury in the opening game of the season.
He had asked Balotelli to step up to the plate during the Argentine's injury lay-off, but now the Italian has joined Aguero on the sidelines.
The 47-year-old will therefore have to rely on the combination of Carlos Tevez and Edin Dzeko to lead the line in the absence of Aguero and Balotelli.