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Dry Eye in Dogs

Robbie’s Story and Dry Eye in Dogs

“Robbie” was a very cheeky, but adorable, Westie Highland White Terrier. He was always a bit of a handful to examine at the surgery when he came in for his usual check-ups. However, much to his annoyance, he had had to be seen quite regularly recently due to recurring eye problems. He had had several bouts of conjunctivitis and sore, irritated eyes. After advised further investigations, a thorough eye examination and a tear test revealed that Robbie had Keratoconjunctivitis sicca , or “Dry Eye", which would require him now to have on going, lifelong, topical eye treatments. 

What is KCS: Keratoconjunctivitis or "Dry Eye"?  

Keratoconjunctivitis sicca describes the changes in the cornea which result from the lack of normal tear production.  

The cornea is the clear structure in the front of the eye. Like all living tissues, the cornea requires a supply of oxygen and food for energy.  This is supplied to the cornea through a three layered ‘tear film’.  The outer most layer of the tear film is an oily layer supplied by glands in the eyelids and it helps to prevent evaporation.  The middle layer is the watery layer produced by the lacriminal gland. The innermost layer is in direct contact with the cornea, and this is a layer of mucous produced by glands located within the conjunctivae. The mucus layer helps the water layer remain attached to the cornea.  KCS or Dry Eye occurs when there is a lack of production or an increased evaporation of the watery layer of this tear film. This then results in a drying of the corneal surface, which can become uncomfortable. When the aqueous tear production decreases, mixing of the oily and mucin layers occurs producing a thick, yellowish, ropy discharge which clings to the eye. Further drying of the cornea surface leads to irritation which can eventually cause damage to its delicate structure. The cornea then rapidly undergoes damage and scarring, that may if untreated then lead to painful corneal ulcers and sadly eventually to partial vision loss.  

There are several causes of Dry Eye, including : immune-mediated inflammation of the lacrimal gland, hypothyroidism, and infections of the eye lacrimal glands.  Also, a loss of nerve impulses to the lacrimal gland may also cause Dry Eye.  Another cause is the toxic effect produced by some sulfa-containing drugs. Some of these drugs may have been given to the patient for the treatment of other diseases. 

The diagnosis of Dry Eye is generally made by performing a “Schirmer” tear test. Using small, sterile, calibrated strips this test measures the volume of tears produced within one minute. A fluorescein stain eye test (a bright green stain test) may also be used to identify a possible corneal ulcer and to assess the rate of the tear film breakup. 

Treatment of Dry Eye is by topical eye drops used for the stimulation of tear production and tear replacement treatments. Providing eye lubrication during the treatment period is particularly important, because keeping the eyes moist decreases any further damage and corneal scarring. Most patients will do well if the medications are administered on an advised, regular basis. Usually these are applied after gently bathing the eyes with warm water and pads several times a day.  Also, the control of eye inflammation and infection may be required through the topical application of topical antibiotic and anti-inflammatory eye treatments. In addition to increasing tear production, there may be a need to reduce the overgrowth of bacteria that is common in the syndrome.  The patient frequently has a build-up of mucus in the folds of the eyelids, which provides an ideal environment for bacterial growth.  These bacteria may not be disease-causing bacteria but do sometimes need to be controlled with an antibiotic. Topical anti-inflammatory drugs may also be used to reduce any inflammation and corneal scarring.  

Often the tear stimulation and replacement treatments required to keep these cases stable are continued for the lifetime of the pet. 

After counselling Robbie’s owner on how to safely bathe his eyes and apply his regular eye drops. Wee Robbie became less mischievous and quite used to his daily eye “spas” as time went on and his eyes soon improved. He seemed to realise that this helped him and soothed his irritated eyes. 

His eyes looked so much better and with regular checks to make sure that his eyes were healthy, he responded very well to his treatments. 

 

Alison Laurie-Chalmers, 

Senior Consultant, 

Crown Vets

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