Clogged Tear Duct

Q. My horse has a clogged tear duct. Our veterinarian tried to blow it out with saline, but couldn't. We are treating her with antibiotic drops, but it doesn't seem to be improving it. She has a "swelling" on her cheek bone area, and it seems to be progressing up toward her eye. What other treatments are available? Is there a surgical procedure and, if so, would it be a realistic option? Are there any consequences of doing nothing further?

Sue, via e-mail

A. It is likely that this horse has a dacryocystitis-causing tear duct obstruction. Dacryocystitis is inflammation of the lacrimal sac and nasolacrimal duct (the tear duct at the nostril), and it is seen frequently in horses.

Dacryocystitis can develop as a primary problem or be secondary to duct obstruction. Eyelid puncta atresia (no opening in the lacrimal duct at the eyelid), nasolacrimal duct agenesis (incomplete duct development), and nasal puncta atresia (no opening in the nasolacrimal duct, the part at the nostril) are congenital abnormalities that can result in severe dacryocystitis. There are many potential causes of acquired obstruction of the nasolacrimal system (fractures, foreign bodies, neoplasias or tumors, granulomas, or sinusitis), although often an underlying cause cannot be determined.

An ophthalmic exam is necessary to identify any primary ocular problems causing a mucopurulent (containing both mucus and pus) discharge or secondary ocular involvement. Patency of the duct (how unobstructed it is) might be assessed by the veterinarian initially by the fluorescein dye passage test. Fluorescein dye is put into the eye, and the nasal puncta is observed for appearance of fluorescein within five minutes. Attempts should be made to flush the duct with saline or irrigating solution from the patent puncta. Topical anesthetic should be applied to both the nasal mucosa and conjunctiva near the openings prior to flushing. Cannulation of the nasolacrimal duct is performed in congenital, chronic, or obstructed cases using a French urinary catheter or polyethylene tubing inserted through the nasal or eyelid puncta. The catheter might appear to hit a blind end several centimeters from nasal opening and should be redirected.

Dental and oral examination should be performed if dental disease is suspected as the inciting cause of dacryocystitis. Aerobic and anaerobic bacterial culture and sensitivity of material flushed from the puncta and duct are beneficial in identi-fying the cause of persistent dacryocystitis. Systemic antibiotics, but not topical antibiotics, penetrate the nasolacrimal duct.

Skull radiographs are valuable if a fracture is suspected from the history or physical exam. Contrast dacryocystorhino-graphy is essential and assists in identifying the cause and location of the obstruction. It involves instillation of 4-6 mL of radiopaque solution (a solution that shows up on an X ray) into the puncta followed by plane-film radiography.

Acquired obstructions are treated by the veterinarian removing the cause when possible, irrigating the duct, and catheterization of the duct for two to three weeks. The indwelling stent catheter is sutured to the skin. Systemic antibiotics are necessary for penetration into the infected tissue.

Acquired obstructions resulting in dacryocystitis are often more difficult for a veterinarian to treat than congenital abnor-malities. Foreign body and periodontal causes have the best response to therapy for acquired obstructions. Cannulation of the duct might be impossible in cases of neoplasias and maxillary fractures, and permanent correction of the obstruction and subsequent dacryocystitis might not be possible.

About the Author

Dennis E. Brooks, DVM, PhD, Dipl. ACVO

Dennis E. Brooks, DVM, PhD, Dipl. ACVO, is a professor of ophthalmology at the University of Florida. He has lectured extensively, nationally and internationally, in comparative ophthalmology and glaucoma, and has more than 140 refereed publications. He is a recognized authority on canine glaucoma, and infectious keratitis, corneal transplantation, and glaucoma of horses.

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