The number of patients needing surgery for disfiguring facial injuries has been reduced by 60 per cent since the introduction of controversial "lockout" laws, according to new evidence presented to a state government roundtable on Sydney's nightlife.

The unpublished research, taken from a database of surgeries at St Vincent's Hospital, was revealed on Thursday by Dr John Crozier, a trauma surgeon and representative of the Royal Australasian College of Surgeons.

"In the two years prior to the introduction of these […] measures, there were 145 people managed for severe facial injuries requiring surgery […] in the two years after the measures there have only been 58.

"We [haven't] in medicine seen such a reduction with a whole range of other measures. Nothing else equates to that level of reduction by a simple legislative change."