The lid is slightly everted and put on the stretch by pulling it downwards and outwards with the thumb. The depression caused by the punctum is seen on the top of a small elevation. The point of the dilator is entered vertically into the punctum and then turned parallel with the lid margin and passed onwards with a steady pressure. At the same time it should be rotated between the finger and thumb, until the inner bony wall of the lachrymal sac is felt. The only difficulty which may be experienced is in entering the dilator into the punctum, owing to the small size of the latter. For this reason the fine point of Nettleship’s dilator is more suitable than the form modified by Lang. Even Nettleship’s dilator is too large in a few cases, and here a large sharp-pointed pin is sometimes of use in defining the punctum before using Nettleship’s dilator. [Illustration: FIG. 163. CANALICULUS DILATOR] SLITTING THE CANALICULUS =Indications.= To enlarge the punctum and direct the entrance to the canaliculus inwards. This is especially desirable before ectropion operations and for the removal of concretions (leptothrix) from the duct. In former days the canaliculus used to be slit with the idea of passing very large probes down the lachrymal duct; this has now been abandoned, since slitting the canaliculus throughout its whole length, as is required for this treatment, does away with the capillary attraction. [Illustration: FIG. 164. CANALICULUS KNIFE.] =Instruments.= Dilator, canaliculus knife (Fig. 164), straight iris forceps, sharp-pointed scissors. =Operation.= It is usually performed on the lower canaliculus. The eye is cocainized as in the previous operation and the patient is made to look up. _First step._ The canaliculus is first dilated. The knife is inserted for a short distance with the handle parallel to the lid margin. The lower lid being held on the stretch by the thumb, the handle of the knife is raised towards the brow, thus dividing the canaliculus. The blade of the knife should be directed upwards and slightly backwards. _Second step._ As the lips of the wound are liable to reunite, it is better to remove the posterior lip of the groove. This is performed by seizing the latter with forceps and dividing it with scissors. The entrance to the canaliculus should be kept open by means of the dilator passed twice a week for a month. SYRINGING THE LACHRYMAL DUCT =Indications.= (i) To test whether the lachrymal canals are patent. (ii) By constantly cleansing the sac and washing away all purulent discharge the mucous membrane may regain a more healthy condition, and so an obstruction due to an alteration in the mucous lining may be relieved. In cases with a purulent discharge a small quantity of protargol (10% solution) may be left in the sac after syringing. [Illustration: FIG. 165. LACHRYMAL SYRINGE.] (iii) The injection of adrenalin and cocaine into the sac before its excision.