Bjornebye sustained a fractured eye socket in a freak training ground incident last April and has been unable to make a full return to fitness.
He told the club's official website: "It was a terrible injury and presented me with a massive challenge, but I have always been positive I could overcome it.
"The will has always been there, but in the end it has not proved realistic.
"I didn't want to be just a footballer, I wanted to play at Premier League level twice a week.
"It's clear now that that's not possible and I have a responsibility to myself, my family and my future."