Connected above through the canaliculi with the conjunctiva, and below
through the lachrymal duct with the nasal chamber this cavity is liable
to be more or less implicated in all cases of nasal catarrh and
conjunctivitis, (strangles, canine distemper, influenza). If the
lachrymal duct is obstructed so that the tears accumulate in the sac,
the tendency to catarrh is further enhanced by the distension and
weakening of its walls, and by the propagation of bacteria which have
entered with the tears, and find in them a favorable and abundant
culture medium; the diameter of the sac in the horse being about ⅔rds.
of an inch. The presence of foreign bodies is another cause.
_Lesions. Symptoms._ Swelling at the inner canthus, which raises the
carnucle above the normal level, and the escape of tears over the lower
lid are the most prominent symptoms. If the swelling is pressed it
subsides, the contents, clear or purulent, escaping through the
lachrymal duct, to the nose, or through the puncta and accumulating in
the inner canthus or flowing over the cheek. The hair beneath the inner
canthus is matted together, or drops off leaving bare patches. Wolff
found in one case, a distension of the sac to over two inches in
breadth, and 1⅔ inches long. To the swelling there is soon added
conjunctival inflammation, closure of the puncta by swelling and the
escape of all tears over the face. Suppuration supervenes in the sac,
and in the larger animals the pent up pus often makes its way outward,
causing destructive ulceration of the walls of the canaliculi and
puncta, or of the walls of the sac, the skin, or even the subjacent
bone. In this way fistula results. Caries of the bone and penetration of
the molar alveoli may ensue. (Girard, Leblanc).
_Treatment._ The first object must be to secure a free drainage into the
nose. The evacuation of the sac by compression having been accomplished,
an astringent solution may be injected through the nasal opening of the
lachrymal duct. If the canal is pervious the sac will be re-filled and
will swell out as before. The injection may be 0.5 per cent. sulphate of
zinc, 1 per cent. acetate of lead, 0.3 per cent. nitrate of silver, 1
per cent. tannic acid, 2 per cent. boric acid, or 0.02 per cent.
corrosive sublimate. Cocaine may be added in the proportion of 5 per
cent. The injection may be repeated thrice a day at first, then twice,
and finally once as the catarrh subsides.
If the injection fails to reach the sac, thoroughly sterilized, flexible
probes may be used, increasing the size as they can be passed without
too great pressure.
Or the puncta and canaliculi may be injected as in the human subject,
the conjunctiva having been first anæsthetized by cocaine, or general
ether or chloroform anæsthesia having been induced. The slitting of the
puncta and canaliculi may be resorted to, as spoken of under atresia.
The frequent passage of a sound is usually resorted to, and a stilet may
even be worn, but there is always danger of resulting thickening and
narrowing of the duct, and, if healing can be secured without this
measure, it is to be preferred.