Watery eyes in dogs: causes and treatment

Overview

How do tears travel from the eye to the nose?

Tear fluid spreads over the eye's surface when your dog blinks. The lacrimal gland produces the watery part of tears. The third eyelid gland also produces this watery component. The surface of the tear film has an oily layer produced by eyelid glands. Its innermost layer contains mucus produced by conjunctival cells. At the inner corner of the eye are 2 small drainage openings, or puncta: one in the upper eyelid and one in the lower. Small channels beginning at these openings join in the lacrimal sac. Fluid then travels from the sac through the nasolacrimal duct into the nasal cavity. If more fluid arrives than the drainage pathway can carry, the excess overflows the eyelid. Tears can also travel along hairs onto the cheek even when the duct itself is open.

Causes

Irritation of the eye's surface

Pain from a corneal ulcer can increase tear production. Allergic conjunctivitis can irritate the eye and make it water. Extra eyelashes or lashes growing in the wrong place can rub the cornea. Thick extra lashes growing towards the eye's surface cause more irritation than fine hairs pointing outwards. An inward-rolling lower eyelid can cause watering when its hairs touch the eye. Sudden watering may accompany inflammation inside the eye, called uveitis.

Narrowed or blocked tear drainage pathways

A tear duct opening may be abnormally small or absent from birth. A plant awn can lodge in the lacrimal sac and cause inflammation. Scar tissue following longstanding inflammation can narrow the drainage pathway. A mass pressing on the tear duct from outside can hinder drainage. Severe inflammatory swelling in the nose or sinuses can close the drainage route. A bony injury beside the duct can damage it. An adhesion between the conjunctiva and eyelid can cover a punctum. A tooth root abscess can sometimes be associated with a blocked tear duct.

Risk factors

In a short-muzzled dog, the nasal end of the lower eyelid may roll inwards so that the punctum does not meet the tears normally. An anatomical study of Pugs, French Bulldogs and Bulldogs included 51 short-muzzled dogs. Their nasolacrimal ducts were 41–57% shorter than those of dogs with normal skull conformation. The small channels between the inner corner openings and lacrimal sac were 2–3 times longer in short-muzzled dogs. The comparison group contained 6 dogs with normal skull conformation. An accessory opening allowing tears to drain further back in the nasal cavity was found in 98% of the short-muzzled dogs.

One northern European Border Terrier breeding report recorded an inadequate tear duct opening in 14 dogs, or 1.9% of those examined. Cocker Spaniels have a recognised predisposition to undeveloped tear duct openings. Shih Tzus were the most common breed in a surgical series of dogs with tearing caused by rubbing hairs or an inward-rolling eyelid at the inner corner.

Typical symptoms

Tear overflow is most commonly visible at the inner corner of the eye.

• The fur below the eye may stay wet.
• A reddish-brown streak may develop on a pale coat.
• The eye may look red if its surface is irritated.
• Your dog may squint because of pain.
• An inflamed lacrimal sac may produce mucus or pus.
• The lower eyelid near the inner corner may become swollen and tender.

Lacrimal sac inflammation, or dacryocystitis, often affects only one eye. Clear, watery tears differ from the thick discharge that often sticks to the eye's surface in dry eye. A foreign body in the lacrimal sac can cause abundant discharge even without squinting. In one series of 38 dogs with dacryocystitis, both eyes were affected in 3 dogs. All 48 dogs operated on for suspected lacrimal sac foreign bodies had one-sided discharge containing mucus or pus.

Complications and consequences

Skin irritation and persistent inflammation

Skin that remains wet beneath the eye can become irritated. Dermatitis may also develop in the damp area. Dacryocystitis can accompany conjunctivitis that persists despite usual treatment. Longstanding inflammation can form a fistula that drains pus onto the skin. If a rubbing eyelid or hair is responsible, a corneal ulcer can develop. Persistent eyelid irritation can also darken the cornea as pigment accumulates on its nasal side. Tears may continue to appear on the cheek if eyelid conformation prevents them reaching the punctum.

Diagnosis at the vet

Examining the eye's surface and eyelids

Your vet examines both eyes even if only one waters. Eyelid margins are checked for inward rolling or rubbing hairs. The inner corner is examined to see whether the puncta are visible. The Schirmer tear test uses a paper strip to measure the tears moistening the eye. The strip is held beneath the lower eyelid for 60 seconds. Its wetted length is measured in millimetres. A usual result is about 15–25 millimetres per minute. Measuring eye pressure helps investigate glaucoma.

Dye testing, flushing and imaging

The Jones test checks whether dye placed on the eye's surface appears at the nostril. A study of healthy eyes tested 73 dogs. Dye appearance was monitored for up to 30 minutes. Transit times varied widely in that study. Dye travelled faster when given as a solution than when a moistened dye strip was applied to the eye's surface. In another eye study, the nostrils of 43 dogs were checked for dye within 10 minutes. In one CT study of short-muzzled dogs, contrast entered the nasal cavity solely through an accessory tear duct opening in 54%. Failure to see dye at the nostril does not establish a blockage, as drainage may open further back in the nasal cavity.

If flushing fluid returns through a punctum, there may be an obstruction in the duct. One dacryocystitis study used flushing to assess drainage pathway patency in 39 of 41 cases. In the remaining cases, the foreign body was already visible in the punctum. Contrast imaging can show where fluid stops within the duct. A plant foreign body does not always show on CT. In a small case series, lacrimal sac ultrasound found a foreign body in 4 of 5 eyes examined.

Treatment

Treatment depends on the cause of tearing

Your vet chooses treatment according to whether the eye produces excess tears or their drainage pathway is impaired. Corticosteroid eye drops must not be used with a corneal ulcer. If abnormal lashes rub the eye, your vet may freeze their follicles. A symptomatic inward-rolling eyelid can be corrected surgically. Reshaping the inner corner can reduce an excessively large eyelid opening. Eyelid surgery aims to preserve the puncta. In a separate series of 23 dogs, tearing stopped in all dogs after inner-corner surgery. In these dogs, tearing was caused by inward rolling at the inner corner or a hair rubbing the eye.

After eyelid correction, discharge decreased in 34 of the 48 dogs whose owners assessed this change (70.8%). In the same survey, eye-area irritation decreased in 21 of 31 dogs (67.7%). Veterinary follow-up recorded postoperative complications in 11 of 104 dogs (10.6%).

Flushing and opening the drainage pathway

Your vet may try to open a tear duct by flushing it with sterile fluid. Flushing can remove loose discharge and sometimes a foreign body. For bacterial infection of the lacrimal sac, your vet may prescribe a topical antimicrobial. An unopened punctum can be opened surgically if needed. A thin tube may be placed in the duct during healing to help keep it open. If the drainage pathway is permanently damaged, a new route can sometimes be created surgically.

In a study of tear drainage endoscopy and stenting, a stent was successfully placed in 14 of 16 dogs (88%). The median time it remained in place was 5.6 weeks. Time in place ranged from 1.3 to 9.4 weeks. Placement failed in 2 dogs whose ducts were narrowed by scar tissue or granulation tissue. Of all 16 treated dogs, owners of 8 reported complete resolution of symptoms.

Removing a plant foreign body

A plant awn in the lacrimal sac can be removed under ultrasound guidance if it is accessible through the punctum. The sac can also be opened surgically through the conjunctiva. Among 48 dogs operated on using this technique, 41 had a plant awn or fragments identified (85%). A stent was successfully placed in 40 of 48 dogs (83%). At the final check, the duct was open in 41 of 47 dogs followed up (87%). Patency was confirmed by flushing at the check-up. The median follow-up period was 34 days. In 2 dogs, the stent became partly or completely dislodged when the dogs interfered with it themselves.

Prevention

Long hairs rubbing the eye's surface can be kept tidy to reduce irritation. Keeping skin beneath the eyes clean and dry helps reduce the effects of constant dampness. Avoid getting shampoo in the eyes when washing the head, to prevent surface irritation. A congenital abnormality of the tear duct opening can be detected during an eye examination. Some Cocker Spaniel breeding guidelines advise against mating two dogs that both have undeveloped tear duct openings. In some official eye screening schemes, an inadequate opening can be recorded as a presumed inherited eye finding.

Important for dog owners

Note whether one or both eyes water and whether the fluid is clear, mucous or purulent. Gently wipe fur beneath the eye with a clean pad moistened with lukewarm water. Accustoming your puppy to calm eye cleaning also makes giving drops easier if they are needed later. Gently dry the skin after cleaning if tears constantly wet it. Do not use hydrogen peroxide-containing stain removers near the eye: a splash can damage it. If a watering eye becomes red and your dog squints, it needs prompt examination.

Frequently asked questions

Does a brown streak mean a blocked tear duct?

A brown streak can develop below the eye when tears repeatedly wet the same area of fur. Tears can also run onto the cheek along hairs at the inner corner. Your vet assesses drainage by examining the puncta and, if needed, performing a dye test.

Why does dye not always appear at the nostril?

Dye transit time varies even in dogs with healthy eyes. In some short-muzzled dogs, fluid can drain through an accessory duct opening further back in the nasal cavity. If needed, your vet can assess patency by flushing or contrast imaging of the drainage pathways.

When could eye discharge indicate dacryocystitis?

With dacryocystitis, mucus or pus may collect at the inner corner of the eye. Discharge is often one-sided and may persist despite treatment for conjunctivitis. If a plant awn is lodged in the lacrimal sac, removal may be needed for symptoms to improve.

Can I flush a tear duct at home?

Tear duct flushing is performed at the veterinary practice by inserting a fine instrument into the eyelid's punctum. With dacryocystitis, flushing may cause tenderness and pus to return through the other punctum. At home, you can wipe tear-wetted fur around the eye with a pad moistened with lukewarm water.

Can eyelid surgery help a watering eye?

Eyelid surgery can reduce tearing when it is caused by an inward-rolling eyelid or a hair rubbing the eye's surface. Reshaping the inner corner can correct eyelid position while shortening an excessively large eyelid opening. If a lacrimal sac foreign body causes the discharge, treatment focuses on removing it.