“Dry Eye Syndrome”
WHAT IS KCS? KCS is defined as a deficiency of tears that occurs commonly in dogs and infrequently in cats.
WHAT ARE THE SIGNS OF KCS? KCS is most commonly a chronic, progressive disorder. It may affect one eye or both. Dogs with a moderately lowered tear production may have a chronic or recurring conjunctivitis (swollen membranes around the eye) with minimal irritation to the surface of the eye. As the tear production further decreases and the condition progresses – tacky, mucoid discharge clings to the eyelids and the surface of the eyes and may stick the lids together. The conjunctiva may become red, thickened and possibly pigmented. The surface of the eye loses its lustre and some animals may have a dry nostril on the affected side. The degree of pain or discomfort varies from dog to dog but blinking and squinting are commonly seen. In some cases, ulcers develop on the surface of the eye, which not only cause pain but can also potentially cause the eye to rupture. KCS most commonly affects predisposed breeds which include the Cocker Spaniel, West Highland White Terrier, Shih Tzu, Lhasa Apso, Cavalier King Charles Spaniel, Bull Terrier, Bulldog, Miniature Schnauzer, Dachshund, Chihuahua, and Pekingese.
WHAT CAUSES KCS?
Present at birth May be due to congenital “hypoplasia” (lack of growth) or a retarded functional development of the tear producing glands. KCS is, however, much more common in older dogs.
Autoimmune adenitis of glandular tissue The majority of cases fall into this category. The structure of the lacrimal gland breaks down due to immune mediated inflammation (i.e. – the body’s own immune system attacks the tear producing gland) and it stops producing tears.
Trauma KCS due to trauma may be the result of damage to the nerves that supply the glands. In some instances, normal function may return over 1-2 months.
Secondary to chronic conjunctivitis The swollen membranes around the eye may cause obstruction of the ducts leading from the glands.
Distemper The distemper virus can destroy the tear producing glands.
HOW IS KCS TREATED?
Medical Stimulation of tear production can be achieved, in many cases, by the use of cyclosporine or tacrolimus eye drops, often combined with corticosteroids and antibiotics. Cyclosporine and tacrolimus not only stimulates tear production and treats the inflammation within the gland tissue, but it also slowly reverses some of the changes on the surface of the eye. It is important to understand, however, that cyclosporine or tacrolimus is only a treatment, not a cure, and will likely need to be used forever. Stopping the treatment results in recurrence of glandular inflammation and causes further damage, which may result in the need for surgery.
Surgical In certain breeds that have protruding eyes (e.g. Pug, Shih Tzu, etc.), surgery to close a portion of the eyelids may help to decrease the amount of moisture that evaporates from the eye.
Dogs that develop corneal ulcers require specific treatment including antibiotic drops or ointments and for deep ulcers, surgery to apply a “conjunctival flap” is necessary to prevent the eye from rupturing. This procedure is performed by attaching a portion of the soft tissue that surrounds the eye directly onto the ulcer. The flap provides protection and support for the weakened cornea and supplies blood directly to the ulcer site, which aids in healing. This flap will remain permanently.
In some cases where medical management with cyclosporine or tacrolimus eye drops or ointment is unsuccessful (after 2 to 3 months of therapy), surgery can be performed whereby the parotid salivary gland duct is removed from inside the dog’s cheek, pulled up into the conjunctiva, and sewn in place to provide lubrication for the eye with saliva. Your pet will be evaluated at the time of examination for parotid duct function by placing a bitter tasting agent on the tongue stimulating salivation. If normal then your pet would be a candidate for parotid duct transposition surgery. Parotid saliva is similar to tears and can act satisfactorily as a tear substitute. This surgery is less commonly required now due the recent advances in medical therapy. It is also not without potential complications, including the precipitation of salivary salts on the margins of the eyelids (this can be treated with medicated drops and frequent cleaning).