'Dry Eye' in dogs

by Shane Jackson M.A., Vet MB., MRCVS





The value of tears becomes apparent to anyone who has had grit in their eye.  Irritation to the front of the eye, the cornea, stimulates an increase of tear production with the result that the foreign body is usually flushed from the eye.  When there is a lack of tears, serious damage can occur to the eye, although these changes can take some time to develop.

‘Dry eye’, known technically as Keratoconjunctivitis Sicca or KCS, is the result of inadequate tear production and is seen in any breed of dog.  Tears are produced from glands around the eye, and are spread over the front of the cornea by blinking. They are not just water, but are actually quite complex in their structure, and they serve several functions.  They lubricate and flush the eye, they provide nutrition and oxygen to the cornea, and they also have a role in preventing bacterial infections of the eye.

The condition can result from a number of causes, including infections such as distemper, from nerve injury, or chemical injury, from aging or from unknown causes.  In some cases it is thought that the body’s own immune system identifies the tear producing glands as foreign material and attempts to destroy them.

In the early stages of KCS the dog can be in a great deal of pain.  The eye may be held closed, the conjunctivae may be inflamed, and there may be profuse, often yellowish, discharge.  Left untreated, the disease progresses to a chronic condition where the pain is usually less marked but the cornea may be cloudy and pigmented, often black.  Ulcers may develop and the surface of the eye does look extremely dry.  Blindness can easily follow because the cornea is so thickened and discoloured.  All of these symptoms are variable; not all of them may be present in KCS, and where some of these symptoms are present, ‘dry eye’ is not always the diagnosis.

Diagnosis of ‘dry eye’ is usually made on the basis of clinical signs, but the amount of tears actually produced can be gauged by employing the tear test.  Special strips of blotting paper type material are gently slipped over the lower lid and held there for a minute.  Although this must be slightly unpleasant for the dog, judging by the reactions we encounter from our patients, it is not painful.  There is a scale on one side of the paper, and the extent to which the tears have flowed down the strip at the end of a minute gives a good indication of whether normal or abnormal amounts of tears are being produced.

Treatment depends on the severity of the condition.  In mild cases, ‘false tears’ which simply lubricate the eye can be applied.  Unfortunately, this needs to be done several times daily.  Topical antibiotic creams are usually required, especially in the early stages, and these are sometimes given with anti-inflammatories (steroids), though not in the presence of corneal ulceration.

There is a surgical procedure available.  The duct leading from the parotid salivary gland, which normally empties saliva into the mouth, can be diverted to the outer cornea of the eye and this means that the saliva then flushes the cornea.  This can be quite successful, except that when the dog is hungry, and therefore salivating a lot, the ‘tears’ overflow the eye onto the face. 

A relatively new treatment is a cream containing the drug, cyclosporin which can be used in other conditions in the body where the immune system is malfunctioning.  Although this drug does not work for all cases of KCS, it seems to have beneficial effects for many.  In some cases that I have treated where the dog is nearly blind, continued use of cyclosporin has resulted in vision returning.  As with so many health problems, the sooner the ‘dry eye’ is diagnosed, the better are the chances of keeping the condition in check.