The Italian striker incurred the damage during a game of squash with his compatriot, Sergio Porrini, in mid-January.
Negri has now returned to training but is still experiencing flashing across the eye and has been told by specialists there is no prospect of him lining up at St Johnstone today.
As four of Negri's 33 goals this season have come in home and away successes against the Saints, the loss is certain to be felt as Walter Smith's men aim to protect a three-point advantage at the top of the Bell's Scottish League Premier Division.
St Johnstone's season has surpassed even their own expectations, with last year's First Division winners occupying a comfortable fifth place in the top flight. Their rise has impressed Smith, the Ibrox manager, who knows his own team's fine record against the Perth outfit will be put to the test at McDiarmid Park.
"St Johnstone are having an exceptional season and have been playing very confidently of late," he said. "That means we will need to show better form than in last week's 2-1 Cup win over Hamilton."Reuse content