The Sheffield fighter was pulled out of the fight in the fifth round by trainer Dominic Ingle as Kazakh destroyer lashed in a number of shots unanswered.
Brook, 30, was obviously struggling after finding the power of Golovkin too much following his move up to middleweight from welterweight to face the WBC, IBF and WBA champion.
But Ingle was also aware his man had suffered a suffered a serious injury in the second round and needed to protect him.
Brook went straight to hospital after the fight for scans and the results have shown he picked up a broken eye socket in the cracking encounter that had fans on the edge of their seat.
The Sheffield man’s promoter said: “Kell has now left hospital – confirmed broken eye socket op on Monday in Sheffield.”
He added: “I’m out of hospital need op next week but will be fine and I’ll be back. Sorry I couldn’t bring it home tonight.”