Dry Eye (Keratoconjunctivitis Sicca)

Condition Overview

Keratoconjunctivitis sicca is a disorder of the tear glands that results in insufficient aqueous (water like) tear production and leads to a dry cornea. The tear film contains less of the aqueous layer and more of the mucus layer.

Symptoms

In a dog with dry eye, the bright, glistening sheen normally seen in the eye is replace with a lackluster appearance in which the cornea is dry, dull, and opaque. Recurrent bouts of conjunctivitis are typical. Eventually the cornea becomes ulcerated or develops keratitis. Blindness may follow.

All symptoms +

Causes

Dry eyes have several causes. Immune-mediated (instigated by the immune system) diseases appear to play a major role. Other causes are unknown. Dry eye is readily seen in Bulldogs, Cocker Spaniels, Lhasa Apsos, West Highland Terriers, and others. Some specific conditions that predispose a dog to dry eye include:

• Injury to the nerves that supply the lacrimal glands (they secrete the aqueous layer of the tear film). A branch of the facial nerve that activates the tear gland passes through the middle ear. Infections in the middle ear can damage this branch, affecting the tear glands as well as the muscles on that side of the face. In this case, the opposite eye is not affected
• Injury to the tear glands themselves. Partial or complete destruction of tear glands can follow systemic diseases such as canine distemper, Addison's disease, and immune-mediated diseases such as rheumatoid arthritis. Bacterial blepharitis or conjunctivitis can destroy the tear glands or block off the small ducts that carry the tears into the eye. A number of sulfonamide drugs are toxic to tear glands. Tear gland injuries may be partially reversible if the underlying cause is eliminated.
• Congenital (defect happening while in the wound) absence of the tear gland is rare, but may occur in the smaller breeds.
• The removal of the third eyelid or the lacrimal gland attached to it can also spark this condition.

Diagnosis

The diagnosis of dry eye is made by measuring the volume of tears. The Schirmer tear test involves placing a commercial filter paper strip into the tear pool at the inner corner of the dog's eye and leaving it in place for 1 minute to measure how much of the strip was wetted. Normally the strip should be wet to a distance of 20mm. In dogs with dry eye, the strip wets less than 10mm.

Treatment

For many years, the frequent application of artificial tears was the only treatment available for dry eye. The FDA has approved ophthalmic cyclosporin and this had revolutionized treatment and greatly improved results. Cyclosporin is an immunosuppressive drug that reverses immune-mediated destruction of the lacrimal glands.

Cyclosporin ointment is applied to the surface of the involved eye. The frequency of application must be determined by your vet. The effect of this treatment is not immediate. Artificial tears and topical antibiotics should be continues until the Schirmer tear test indicates that the volume of tears is adequate.

Treatment is lifelong. Interrupting cyclosporin for as little as 24 hours causes symptoms to reappear in 90% of dogs. This can be reversed by resuming treatment.

When damage to the lacrimal glands leaves little or no functioning tissue, cyclosporin is not likely to be effective. Artificial tears (drops and ointments) prescribed by your vet must then be applied to the dogs eyes several times daily for life. Ointments are less expensive and do not need to be applied as frequently as drops. Saline drops should not be used because they aggravate the problem by washing away the lipid layer of the tear film.

A topical mucolytic agent containing acetylcystine may be recommended to reduce heavy mucus accumulation. Topical antibiotics are indicated whenever the mucus discharge becomes purulent. Topical corticosteroids may be prescribed by your vet in some circumstances to decrease inflammation. In the presence of corneal ulceration, corticosteroids are contraindicated because they may instigate the rupture of the cornea.

Surgical treatment can be considered as a last resort when medical management fails. The operation involves transplanting the duct of the paraotid salivary gland up into the corner of the eye. The saliva takes the place of the tears. The operation has several significant disadvantages. One is that the volume of tears may be more than the drainage system can handle. This can result in a watery eye and accumulation of mineral deposits on the cornea and face.

Prevention

There is currently no known preventative for this condition.

Support

Please contact your veterinarian with questions regarding this condition.