Fig. 163. Canaliculus Dilator
Operation. The operation is performed under adrenalin and cocaine, a little solid cocaine being rubbed in over the canaliculus.
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.
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.
Fig. 164. Canaliculus Knife.
Instruments. Dilator, canaliculus knife (Fig. 164), straight iris forceps, sharp-pointed scissors.