Dry eye syndrome is an inflammation of the cornea and conjunctiva resulting from a lack of aqueous portion of tears. It is a common eye disease in dogs (incidence of approximately 1%). It rarely occurs in cats. The incidence is greater in dogs over 7 years. Some breeds are predisposed, including the American Cocker, Bulldog, West Highland Terrier, Lhasa Apso, Pekingese, Boston Terrier, Doberman Pinscher, Chihuahua, Dachshund and German Shepherd.
The clinical signs observed are pain (manifested by the blepharospasm), conjunctival redness, swelling, mucous or mucopurulant discharge. In the chronic phase of the disease, we may observe a superficial vascularization of the cornea, as well as corneal pigmentation and ulceration. Untreated, the disease will lead to a reduction in or loss of vision.
In the majority of cases, the disease is auto-immune, but it can also be congenital, neurological, drug induced (general anesthesia, atropine, sulfa type drugs) or, may occur following surgical removal of the nictitating gland, radiotherapy, systemic diseases (eg. hypothyroidism, diabetes mellitus, canine distemper or feline herpes virus), chronic conjunctivitis (cats) or chronic blepharoconjunctivitis (dogs). Diagnostic procedures performed when the disease is suspected include the shirmer test, which measures tear production, and the fluorescein staining test to assess the presence of corneal ulcers.
The goal of treatment is to stimulate tear production, keep the eye moist, relieve pain, control inflammation, bacterial infections and secondary corneal ulcerations.
The ointment often used is cyclosporine, which improves tear production in 80% of patients. A shirmer test performed 4 to 6 weeks after starting the treatment allows us to evaluate the response to treatment. Other topical medications (tacrolimus, pilocarpine) may be used in cases where there is no response to cyclosporine or if the disease is of neurological origin. In addition, topical antibiotics may be prescribed if there is the presence of bacterial overgrowth in the eye. Artificial tears and lubricating ointments help to moisten the cornea, but the effect is transient, so they must be applied frequently. It is necessary to use them early on in treatment (until tear production increases). In most cases, treatment must be continued throughout life.
The transposition of the parotid duct is a surgical procedure that should be considered when medical treatment is ineffective(when destruction to complete immunitary mediation of the lacrymal gland or principally of congenital origin of dry eye syndrome ).The lubrication of the eye will be accomplished by secretions from the parotid salivary gland.
Complications are common: calcium deposit on the cornea, excessive eye secretions causing secondary facial dermatitis and occlusion of the parotid duct secondary to scarring. Fortunately, this procedure is rarely needed given the good response to cyclosporine.
Élise Lavallé, D.M.V.