Obliteration of the lachrymal duct may occur from stricture of the
canal, the result of wounds or other irritants: from pressure by the
inflamed mucosa in nasal catarrh or strangles: from polypus or osseous
tumor in the nose: from actinomycosis or other disease of the bones.
The one manifest _symptom_ is the escape of the tears on to the face. To
complete the diagnosis, injection of one punctum will cause distension
of the lachrymal sac.
_Treatment._ This may be attempted by bougies. In the _horse_ a small
sound, metallic or whalebone bougie, thoroughly sterilized and smeared
with aseptic vaseline, or oil, is inserted from the nasal opening and
carefully passed on into the sac. In the _dog_ the nasal opening cannot
be reached and the bougie must be passed by the puncta and lachrymal
sac. To secure the requisite dilation, it is usually necessary to probe
the passage daily, using a larger probe when the first passes easily,
until the canal has been sufficiently dilated.
A second resort is to distend the canal by a liquid injection thrown
into the nasal opening. This will succeed when the obstruction is only
caused by concretions in the canal.
A somewhat similar resort is the insufflation of the duct by means of a
finely pointed tube inserted from below into the nasal orifice of the
duct.
Still another method is to make a new opening for the escape of the
tears into the nose. When the stenosis is at or near the nasal opening
of the duct, an artificial opening is easily made and usually
satisfactory. Under anæsthesia, a sterilized silver probe is passed
through the upper punctum, the sac and canal. When it meets definite
obstruction its position is ascertained inside the nose, and an incision
is made so as to allow its escape. The constant escape of tears tends to
prevent it from closing up again, but it is well to examine into this
until it has thoroughly healed. A silk thread worn in the duct and held
in place by a copper or aluminum ring on each end may be resorted to.
Attempts have been made to establish a new outlet by boring through the
lachrymal bone into the nose, but without a permanent success. It has
also been advised to obliterate the lachrymal ducts and sac, on the one
hand and to excise the lachrymal gland on the other, but the proposed
cure is worse than the disease.