The father of a Christchurch man who was stabbed in the head at a party says the calm demeanour of a police officer helped saved his son.



Police received multiple calls early yesterday morning about trouble brewing at a party on Flockton St.



They arrived to find a 20-year-old man had been stabbed in the head and was being supported by his father and friends.



The man underwent surgery yesterday to have the knife's nine centimetre blade removed and was in a stable condition in Christchurch Hospital today.



The man's father said his son's friends were ''absolutely disgusted'' by what had happened, but had told him it was common for young people to carry knives.



''If they didn't have knives it wouldn't have happened. I was at that party, I could have been stabbed, it could have been anyone.''



He now wanted to see a law change to stop people carrying dangerous weapons and to allow police to search people they suspected of carrying of knife.



''Something good has to come out of this. We've got to stop.



''It should be illegal for a person to carry a weapon. Why would a person be carrying a knife if they're not planning to use it.''



The man's father said the police officer who helped him at the scene was "absolutely fantastic".



"People were all distraught, but he just ... settled everybody down. He also steadied me as well."



He also praised the actions of the other police officers at the scene, who kept the party-goers calm, as well as the work of ambulance and hospital staff.



Constable Carl Christensen said he realised the situation was a ''slightly bigger issue than initially thought'' when he saw the knife in the man's head.



''The male was conscious and speaking to me, which was probably the most surprising thing.''



He could see about 1cm of blade, but did not know how much was inside the man's head.



''He made the off-hand comment that he had tried to pull it out himself and I said well we're not going to try that again.''



Christensen's background as an ambulance and air force paramedic meant he automatically knew not to try pulling the knife out.



He went to Christchurch Hospital with the man and was surprised when his x-ray results came back.



''We were all pretty shocked. We were expecting a 3cm blade, not 9cm.



''I don't think I'll come across it again in my career.''



Professor Helen Danesh-Meyer - a specialist eye surgeon who is based at the Eye Institute - last night said the officer's quick actions had probably saved the injured man from further optic damage.



"He has done the right course of action . . . in general principles, it was a very appropriate action to take," Danesh-Meyer told the Sunday Star-Times.



"It depends on the path of the knife and how it is removed; the removal can actually cause more damage than the actual introduction of the knife . . . depending of whether it is going through the optic nerve or the retina.



"Unless you know what you are pulling out and what anatomical structures are coming across in the path, the appropriate thing to do is not pull it out. It is the same with glass or, sometimes, nails."



Christchurch police said on Saturday that they had arrested a 20-year-old at the scene. He had been charged with wounding with intent to cause grievous bodily harm.

SIGHT SAVED: An X-ray of the knife embedded in the stabbing victim’s head.