Posted: 28/01/2017 at 17:52
First of all pruning deciduous Berberis is normally done after flowering, but as long as you do not mind losing any flowers, you may do it now.
You may cut all those stems back to just a few inches above ground level. They will then produce lots of new stems during the year.
Might be worth giving them a feed with a high nitrogen fertiliser afterwards to get them to make new leaves.