Dog - Dry Eye - Keratoconjunctivitis sicca (KCS)

Keratoconjunctivitis sicca (KCS) is commonly called dry eye. This is a very apt name since the condition results from lack of proper tear production so that the eye has a dry and sore appearance.

How is it caused?

Tears are mainly composed of a watery (aqueous) substance, but also contain mucoid (slimy) and fatty fractions. Their composition is actually quite similar to saliva. Any problem which affects the ability of the tear glands to produce adequate amounts of the aqueous fraction can result in ‘dry eye’ since the quantity of tears produced is insufficient to keep the eye lubricated and free from infection which are two of the important functions of tears.

What are these problems?

There are many factors that can contribute to KCS. Among the most common are:

• Autoimmune problems resulting in self-destruction of the tear producing glands
• Systemic disease, e.g. canine distemper in unvaccinated dogs and feline herpes virus (‘flu’) in cats
• Certain drugs, e.g. some sulphonamides
• Hypothyroidism and diabetes mellitus (sugar diabetes)

Are some breeds more prone than others

West Highland White Terriers, American Cocker Spaniels, Lhasa Apsos and Yorkshire Terriers appear particularly prone although any breed, including crossbreds, can be affected. Occasionally puppies can be born with a congenital form, where the tear producing glands fail to develop normally. This can occur in toy breeds especially Cavalier King Charles Spaniels.

Autoimmune problems, particularly in the West Highland White Terrier appear to be by far the most common cause.

At what age does it occur?

Usually the condition affects middle-aged or older dogs. The congenital form is rare but does affect puppies from a very early age.

What are the symptoms?

KCS can sometimes occur very rapidly (acute onset KCS). Pain and a tightly closed eye, sometimes with corneal ulceration are the usual signs and urgent treatment is required. However the more common form is slow in onset (chronic KCS) and the eye appears uncomfortable rather than painful. Conjunctivitis is usually present so that the eye appears reddened. There is a lack-lustre appearance of the cornea (clear part of the eye) and a sticky discharge.

Tears have an antiseptic action and their reduction can result in infection. This secondary conjunctivitis can mask the true nature of the underlying problem. The cornea can become ulcerated and vascularised (blood vessels within the cornea). With reduction in the aqueous portion of the tears the mucin fraction increases resulting in the yellow sticky discharge which is often a prominent sign of KCS. This discharge is very difficult to bathe away.

Both eyes are usually affected although one is often worse than the other.

How is it diagnosed?

Diagnosis is made on the clinical signs and measurement of tear production using a simple test called the Schirmer Tear test. This involves placing small strips of special paper into the eye, under the eyelids, which measure the amount of tears. The test does not hurt the patient at all. Affected eyes produce fewer tears than normal. In severely affected cases sometimes virtually no tear production can be recorded.

Is there any treatment?

Topical  treatment (eye drops) has two aims – to stimulate natural tear production and to supplement with artificial tears. In recent years the introduction of immune suppressant eye ointments has revolutionised the treatment of ‘dry eye’ since they directly stimulate the tear gland to produce more aqueous tears. They are often combined with other treatments including artificial tears in the form of drops or ointments. Antibiotic and corticosteroid eye preparations are sometimes also used.

The medication will be required life-long – KCS is a condition which can be successfully treated, but cannot be cured.

Regular, gentle cleaning of the eye and eyelids is also very important. To be effective all topical medication has to be applied regularly and methodically. We will show you how to do this and discuss the nursing commitment with you. If you have any difficulties or have any concerns do not hesitate to contact us.

What happens if I cannot do the necessary cleaning and medication?

If medical management proves too onerous or, if after a reasonable time topical treatment is not bringing about the desired result we will discuss the possibility of surgery with you. This involves redirecting the course of the salivary gland duct so that it discharges into the eye (parotid duct transposition). It was mentioned earlier that tears and saliva have many components in common.

This operation is often very successful but it can carry its own complications. It must be considered a salvage procedure where medical management is unsuccessful. It is a specialised procedure and we may refer you to a specialist veterinary ophthalmologist.

Can the problem be prevented?

• Adequate protection against canine distemper and cat ‘flu’ will eliminate KCS caused by these systemic diseases.
• In KCS prone breeds avoid any drugs known to be associated with the condition.
• In dogs with hypothyroidism and diabetes mellitus (sugar diabetes) tear production should be tested on a regular basis.
• The most common cause, due to autoimmune problems, cannot be anticipated nor prevented at present.

What is the prognosis?

This depends on the cause. Drug induced KCS or that due to hypothyroidism or systemic disease can resolve once the underlying cause is tackled. Most cases due to immune mediated problems can be controlled but must be adequately treated which can be extremely time consuming and requires regular monitoring and lifelong treatment.