Conjunctivitis in Dogs

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Overview of Canine Conjunctivitis

Conjunctivitis is an inflammation of the conjunctiva, which is the tissue coating the eye and lining the eyelids. Normally, the conjunctiva is moist and glistening with tiny blood vessels coursing through the semilucent tissue. It serves as a protective barrier for the dog’s eye by trapping debris and helping to prevent invasion of viruses and bacteria.

Conjunctivitis is a common eye problem in dogs. It may be the only eye disease present, or may be associated with other diseases or eye problems.

Causes of Conjunctivitis in Dogs

  • Viral infections that affect the eye, such as canine distemper
  • Bacterial eye infections
  • Certain parasites of the conjunctiva or eyelids
  • Corneal diseases
  • Disorders of the tear ducts or of tear production
  • Eyelid infections or abnormalities
  • Exposure to foreign material such as plant material, fibers, sand and chemicals
  • Trauma
  • Allergies
  • Idiopathic, meaning that no cause is ever defined
  • Other illnesses, such as skin diseases, that can affect the eyelids and conjunctiva
  • What to Watch For

  • Redness of the eyes
  • Eye discharge
  • Swelling of the conjunctiva
  • Squinting or excessive blinking
  • Occasional pawing or rubbing at the eyes
  • Diagnosis of Conjunctivitis in Dogs

    Conjunctivitis is usually diagnosed based on physical exam findings. Your veterinarian will probably perform the following tests:

  • Fluorescein staining to detect superficial abrasions or ulcers on the cornea
  • Schirmer tear test to determine if your dog is producing sufficient tears
  • Thorough exam of the conjunctiva, external eyelids and the third eyelid

    In some situations, additional tests may be recommended, such as:

  • Bacterial cultures
  • Tests for distemper virus
  • Tonometry, which measures eye pressure (glaucoma test)
  • Conjunctival scrapings to evaluate the cells of the conjunctiva
  • Conjunctival biopsy (rarely performed)
  • Certain blood tests if the animal is also ill
  • Treatment of Conjunctivitis in Dogs

    Treatment involves symptomatic therapy for the conjunctivitis and specific therapy for any underlying causes.

  • The eye may be thoroughly irrigated to remove any irritating substance.
  • Foreign material should be removed.
  • Tear production abnormalities are treated with medication.
  • Eyelid infections and abnormalities may require either medication or surgery.
  • Since secondary bacterial infections are a common concern, antibacterial eye ointment is frequently prescribed.
  • In many cases, anti-inflammatory eye medications are also indicated.
  • Home Care and Prevention for Dogs with Conjunctivitis

    If you suspect that your dog has foreign matter in the eye, flushing with sterile eye irrigation solution can help dislodge the offending material. If flushing the eye is not possible or effective, prompt examination by a veterinarian is recommended.

    Once diagnosed and started on medications, the eyes should be checked frequently for improvement. Most cases of conjunctivitis improve within 24 to 48 hours after medication is begun. If you notice that your dog is not improving, consult your veterinarian.

    Unfortunately, many causes of conjunctivitis are not preventable, but veterinary examination and treatment usually resolves the disease rapidly and maintains your dog’s eyes and vision. To prevent conjunctivitis due to foreign matter in the eye, try to prevent exposure to potentially damaging items. Be very careful when bathing your dog to prevent shampoo from getting in the eyes.

    Information In-depth for Dogs with Conjunctivitis 

    Canine conjunctivitis is a common eye ailment. It may occur alone or secondary to another eye disease. Finding and treating the underlying eye problem can prevent or diminish future episodes of conjunctivitis. In some instances no cause is ever defined for the conjunctivitis, but there are a variety of diseases that can produce conjunctivitis.

  • Keratoconjunctivitis sicca (KCS or dry eye). With KCS there is inadequate production of the watery component of the tears. As a result, the surface of the eye becomes dry, irritated, inflamed, and infected. Signs of dry eye include a thick, ropey mucus-type discharge, corneal scarring, and sometimes squinting. The conjunctiva is usually red and inflamed.
  • Upper respiratory diseases, as with kennel cough. These infections involve both bacteria and viruses. Signs of conjunctivitis are often present in both eyes, and other signs such as coughing, sneezing, nasal discharge, lethargy, fever and decreased appetite may be noted.
  • Mechanical irritation. Usually this chronic irritation is due to problems in the development of eyelid and eye lashes. Eyelids may be rolled inward, which causes the eyelashes to rub continuously against the cornea. Loose and drooping eyelids may not be able to close completely and may lead to dry eye. Some dogs may have eyelashes that grow in the wrong direction and rub against the cornea. Some dogs may even have eyelashes that grow from areas other than the eyelids, which may be directed at the cornea and cause constant irritation.
  • Foreign matter. Pieces of sand, plastic, metal, or grass can lodge under the eyelids and create a profound irritation of the eye.
  • Environmental irritants. Cigarette smoke, dust, exhaust fumes, household chemicals, lawn and garden sprays, pollen and other plant material, may cause conjunctivitis. Such irritants may cause a certain type of conjunctivitis, called follicular conjunctivitis, particularly in young, growing dogs.
  • Infection and inflammation of the eyelids and cornea. Because the conjunctiva is physically adjacent to both the eyelids and the cornea, any infection or inflammation of these tissues may result in conjunctivitis. Examples include corneal ulcers, certain forms of keratitis, blepharitis (inflammation of the eyelids), and skin diseases that affect the eyelids.
  • Allergies. Allergy-related conjunctivitis is common in the dog and is most often associated with atopy (inhalant allergies). With allergic conjunctivitis, the conjunctiva becomes red, the eyes are often itchy, and watery discharge may be seen.
  • Parasites. Parasites on the surface of the eye are rare in North American, but occasionally the Cuterebra fly larva may grow near the eye, or small Thelazia worms may occur on the surface of the eye.
  • Primary bacterial infections. Without associated eye disease, these infections are a rare cause of conjunctivitis. It is much more common for bacteria to take advantage of inflamed conjunctiva, and then to invade this inflamed tissue to create a secondary infection.
  • Trauma to the conjunctiva, eyelids, cornea or eye itself.
  • Inflammation from within the eye. Occasionally outward extension of inflammation can reach the conjunctiva, resulting in conjunctivitis. In these instances inflammation within the eye is the primary concern.
  • Any illness. Conjunctivitis may also develop anytime a dog is ill and not feeling well. Discharge from the eyes is common in diseases causing lethargy and fever.
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