Nasolacrimal Duct Obstruction in Horses

Nasolacrimal duct obstruction is a blockage somewhere along the tear drainage system. In horses, tears normally move from the eye through small openings called puncta, then into the lacrimal sac and down the nasolacrimal duct to an opening inside the nostril. When that pathway narrows or plugs, tears spill over the eyelids instead of draining normally.

The most common thing pet parents notice is epiphora, or chronic tearing. The hair below the eye may stay damp, the skin can become irritated, and the horse may develop repeated mild conjunctivitis that does not fully clear until the drainage problem is addressed. Some horses have a simple blockage from debris or inflammation. Others have a more complex problem, such as trauma, scarring, congenital atresia in foals, or compression from nearby swelling or bony change.

This condition is often manageable, but it should not be assumed to be harmless. A watery eye can also happen with corneal ulcers, uveitis, foreign material, or other painful eye disorders. That is why a horse with ongoing tearing should have the eye itself examined, not only the tear duct.

In horses, nasolacrimal duct obstruction is often linked to inflammatory debris inside the tear sac or duct. Merck notes that obstruction of the tear sac and attached duct may be caused by inflammatory material, foreign objects, or masses pressing on the duct. In practical terms, that means a horse may start with mild irritation or infection, then develop poor tear drainage that keeps the eye wet and inflamed.

Trauma is another important cause. A kick, fall, halter injury, or other facial injury can scar, narrow, or physically disrupt the duct. Published equine case reports also describe obstruction where the duct passes near facial sutures, especially when trauma leads to bony proliferation or exostosis around the lacrimomaxillary area.

Foals can be born with a congenital problem, especially atresia of the distal nasolacrimal duct, where the normal opening into the nostril does not form correctly. Merck describes this as a common cause of early epiphora and chronic conjunctivitis in foals. Less commonly, chronic obstruction can be related to masses, severe scarring, or permanent duct damage that requires referral-level care.

Diagnosis starts with a full eye exam. Your vet will want to make sure the tearing is really coming from a drainage problem and not from a painful eye condition such as a corneal ulcer or uveitis. That usually means checking the eyelids and conjunctiva, looking for corneal damage, and examining the area around the medial canthus and nostril opening.

If a tear duct problem is suspected, your vet may try to flush the duct with sterile saline. Merck notes that this is a common first step when obstruction is suspected. A successful flush can both confirm the problem and sometimes treat it if the blockage is made of soft debris. If the duct does not flush normally, or if the problem keeps returning, your vet may recommend imaging.

For longer-standing or more complex cases, contrast radiographs of the skull, called dacryocystorhinography, can help locate the blockage. Merck specifically notes that skull x-rays after dye injection may be needed to determine the site and cause of long-term obstruction. Referral hospitals may also use endoscopy or CT, especially when trauma, facial swelling, exostosis, or a mass is suspected.

Not every case can be prevented, especially congenital problems in foals or obstruction caused by facial trauma. Still, good eye and head care can lower the risk of secondary blockage from inflammation and debris. Ask your vet to examine any horse with repeated tearing rather than treating it as routine irritation over and over.

Prompt attention matters. Early treatment of conjunctivitis, facial wounds, and swelling near the eye or nose may reduce the chance of scarring around the duct. If your horse has had a kick or other head injury, monitor closely for new tearing, facial asymmetry, or tenderness over the lacrimal and maxillary regions.

Daily management helps too. Keep dust, chaff, and irritating debris as low as practical, especially for horses with sensitive eyes. Gently clean tear overflow from the face so the skin does not stay chronically wet. For horses with a history of recurrent obstruction, your vet may recommend periodic rechecks and, in some cases, repeat flushing before the problem becomes more established.