What is conjunctivitis?
The conjunctiva is the lining tissue that covers the globe of the eye (the eyeball) and lines the eyelids and the third eyelid. Conjunctivitis refers to inflammation of this tissue.
What are the clinical signs associated with conjunctivitis?
The most common clinical signs of conjunctivitis include discharge from the eyes (watery, mucoid, or mucopurulent), squinting or excessive blinking, and redness or swelling around the eyes. Conjunctivitis often involves both eyes but one eye may be affected in certain conditions. Conjunctivitis may occur with other clinical signs such as nasal discharge, sneezing or coughing.
What causes conjunctivitis?
The most common causes of conjunctivitis include bacterial and viral infections, allergies, hereditary conditions, and tumors. Conjunctivitis may occur secondary to another eye disease.
Bacterial infections that are not associated with another condition such as keratoconjunctivitis sicca ("dry eye") are rare in adult dogs.
However, puppies can have bacterial infections even before their eyes are open.
- Viral infections such as canine distemper virus
- Immune-mediated disorders such as allergic conjunctivitis (especially common in pets with atopy or seasonal allergies), plasma cell conjunctivitis (especially German shepherds), and Pemphigus.
- Tumors of the eyelids and conjunctiva are rare
Conditions such as nodular episcleritis in collies and mixed collies should be monitored.
Tear film deficiency such as keratoconjunctivitis sicca (KCS or "dry eye") is a common cause of conjunctivitis in dogs.
Lid abnormalities such as entropion or ectropion and eyelash disorders such as distichiasis and ectopic cilia often cause conjunctivitis.
Obstructed nasolacrimal or "tear" ducts can cause inflammation of the tissues surrounding the globe of the eye.
Trauma to the eye or irritation from foreign bodies, smoke, or other environmental pollutants can cause inflammatory conjunctivitis.
Other eye disorders such as ulcerative keratitis, anterior uveitis, and glaucoma can cause conjunctivitis in dogs.
How is conjunctivitis diagnosed?
The primary goal of diagnosis is to determine if the conjunctivitis is a primary or secondary problem, if there is additional disease or damage to the eye, if the condition is allergic, or if it involves the tissues of the eye itself (sclera). In order to differentiate many of these conditions, a complete and detailed ophthalmic examination must be performed. This will include close study of the adnexa (eyelids, eyelashes, tear ducts, third eyelid, etc.), tear production tear (Schirmer tear test), corneal stain to ensure that the cornea is not damaged, and measurement of intra-ocular pressure to rule out glaucoma. Additional tests that may be performed include nasolacrimal duct flushing, culture and sensitivity tests, conjunctival cytology, or biopsy and allergy testing.
How is conjunctivitis treated?
Treatment is directed at the specific cause and may include both topical and systemic medications. Topical gentamicin, tobramycin, chloramphenicol, oxytetracycline, ciprofloxacin, and triple-antibiotic ophthalmic ointments and solutions are commonly prescribed. Some patients will receive medications containing anti-inflammatory agents such as ophthalmic prednisolone or dexamethasone. In dogs that have secondary conjunctivitis, oral antibiotics or anti-inflammatory medications may also be used. Patients diagnosed with KCS will most often be treated with tear-production stimulating agents such as cyclosporine or tacrolimus. Surgery may be performed on patients with eyelid or eyelash abnormalities.
Will my dog recover from conjunctivitis?
Most dogs have an excellent prognosis in most cases of conjunctivitis. Severe, chronic, or recurrent conjunctivitis may have a guarded prognosis based on the definitive diagnosis. Conditions such as KCS and immune-mediated disorders may require lifelong therapy.
Based on material written by Ernest Ward, DVM. and modified with permission from Lifelearn Inc.
© Copyright 2005 Lifelearn Inc.
