Defendant William Stephen Scott, 40, of Oxley Road, Preston, admitted a charge of wounding following the incident on May 1 last year at the Golden Cross pub on Lancaster Road, Preston.
The punter was angry at the teasing behaviour towards the pensioner by Romeo Frith and his friend Ryan Killeen and became involved in an argument with them, Preston Crown Court heard.
Prosecuting, Richard Archer said: “The complainant was in the pub with Ryan Killeen when he encountered another gentleman who was wearing a hat. “It appeared to be Ryan who noticed that hat and he grabbed that hat off the man.
"Mr Frith accepted he was drunk and that the pair were acting silly. They then became involved in an argument that the elderly gentleman was being treated in the way he was.
"Mr Frith accepts he became involved in the argument and he asked the defendant, who is known to him as Billy, 'What are you going to do about it?'
"He accepted it was partly said in a confrontational way. He accepted Mr Scott was clearly angry with Ryan Killeen. He said as a result the defendant began to square up to him."
The court heard Scott struck Frith under his eye. Frith was then removed from the pub and in his anger punched a wall and suffered a broken knuckle
He had suffered seven superficial and two longer cuts beneath his eye that needed glueing.
In interview Scott said he hadn't realised he was still holding the glass bottle.
In a victim personal statement Frith said his young child was frightened by his appearance and he had become "anxious and depressed as a result of the injury", which affected his employment as a sales person at a car showroom.
Janet Ironfield, defending, said several references had been given to the court about Scott and said: "It may well be he perceived a greater and more imminent degree of threat.
"Both are known to each other it is most unfortunate that what happened happened, but the defendant's attitude is one of remorse and regret."
Recorder David Swinnerton said: " It seems that someone had taken the hat from an elderly man in the pub and Ryan Killeen had taken it and thrown it across the bar, he says playing some sort of hoopla game trying to land it - no doubt not amusing to the man whose hat it was.
"You took that man's side in that you decide to intervene and challenge him.
"You had a drink in each hand you were swinging from and you swung at him with the bottle in your hands."
He agreed to suspend his 12 month jail sentence for two years.