1. Those which are undertaken for the relief of the obstruction.
2. Those which are undertaken for the obliteration of the canals.
Except under exceptional circumstances, the latter operations are only undertaken when a cure cannot be brought about by the former.
The presence of a septic focus, such as a distended lachrymal sac, apart from the irritation and increased lachrymal secretion caused thereby, is a source of grave danger to the eye if not relieved, as it is a frequent cause of serpiginous corneal ulceration.
OPERATIONS FOR THE RELIEF OF LACHRYMAL OBSTRUCTION
DILATATION OF THE CANALICULUS
Indications. (i) Contraction of the puncta following marginal blepharitis, especially when associated with ectropion.
(ii) Preparatory to syringing or probing.
(iii) To dilate a stricture of the canaliculus.
Instruments. Nettleship’s canaliculus dilator (Fig. 163).