When may medical staff come onto the field during play?

Under SA Rugby's Protocol for Medical Personnel Entering the Field of Play:

• Qualified medical staff need the referee's permission. It can be given before the match (for example in the change room) or by the referee stopping play and calling them on. If it wasn't given beforehand, they must arrange it with the referee before kick-off, and the referee should not unreasonably refuse.
• If they go on while play continues, they must not interfere with play or put themselves or players at risk. They must keep watching where play is going.
• The referee stops play if it comes within about 10 metres of medical staff treating an injured player. The assistant referees should warn the referee if he or she is unsighted.