It maybe difficult to maintain the patency of the lacrimal system in some cases of congenital obstruction after chronic infection or after trauma. Intubation is carried out using silicone tubing to which is attached a stainless steel wire probe which has a knob on the end. This is engaged by a special hook which is used to draw the wire out from under the inferior turbinate. After leaving the tubes in place for 4 to 6 months the obstructed area is usually epithelialised.