Keratoconjunctivitis Sicca is a painful genetic disorder that is also known as Dry Eye Syndrome, keratitis sicca or KCS.
KCS is an inflammation of the cornea and conjunctiva due to an inability to produce watery tears. KCS prevents the eyes from being properly moistened, resulting in chronically dry, burning eyes and scarring.
With chronic KCS, the corneal surface thickens and becomes irregular resulting in pigmentary keratitis which eventually leads to irreversible blindness. In severe or chronic cases, keratitis may occur with erosion and painful ulceration of the corneal surface and photophobia (intolerance to light). Changes in the eye surface with decreased tear production predisposes the corneal surface to bacterial infections.
The most frequent cause is believed to be immune disorder that leads to decrease of watery component of the tear film. Approximately 72% of the dogs with KCS have the disease in both eyes. Other causes include:
- Autoimmune – The commonest cause of Dry Eye is the dog’s own immune system. Usually this works to protect the animal against disease. However, in cases of dry eye, the immune system identifies the dog’s own tear glands as ‘foreign’, and attempts to destroy them. As a result, tear production is progressively reduced, and left untreated, can be lost all together.
- Congenital – Some dogs are born with defective tear glands.
- Trauma – Damage or inflammation of the tear gland or of its nerve supply.
- Drug Reaction – Certain drugs can cause KCS, including sulphonamide antibiotics or sulphasalazine (used in the treatment of colitis), aspirin and anesthetic agents, which can produce temporary decrease in tear production, sometimes close to zero tear production following 1 hour of anesthesia.
- Viral or Bacterial Infections – e.g. Canine Distemper, Feline Herpesvirus.
- Hormone Imbalance – e.g. Hypothyroidism (underactive thyroid gland).
- Idiopathic – This means there is no identifiable cause. This is due to the limit of our knowledge of this disease, and in due course, further causes are likely to be discovered.
KCS is a surprisingly common condition; in a study of dogs with eye problems, 40% were diagnosed with KCS.
Age at onset: KCS can occur at any age, but is most commonly seen in dogs of 6 to 10 years of age.
- American Cocker Spaniel
- Bull Dog
- Jack Russel Terrier
- Labrador Retreiver
- Lhasa Apso
- Miniature Schnauzer
- Shih Tzu
- Springer Spaniel
- Yorkshire Terrier
- West Highland Terrier
Symptoms: The earliest symptom of Dry Eye is conjunctivitis, or inflammation of the inner eyelids. Other symptoms include:
- chronic redness of the eye
- chronic thick, yellow-green discharge, especially in the morning
- the development of a film over the cornea
- dogs will often show signs of discomfort by squinting and rubbing their eyes
Genetics: The genetics of KCS in all breeds mentioned above has not been investigated.
However, in Cavalier King Charles Spaniels, KCS can be linked with another condition called Curly Coat Syndrome, and is often refered to as Dry Eye/Curly Coat or DE/CC. A recessive DNA mutation linked to KCS and curly coat syndrome (ichtyosiform dermatosis) in Cavalier King Charles Spaniels has been identified and serves as the basis for a genetic test available from Animal Health Trust. In addition to eye problems associated with KCS, dry eye and curly coat (DE/CC) affected dogs have very flaky and dry skin, particularly around the foot, which can make standing and walking difficult and painful. This syndrome appears to be a problem unique to CKCS and most dogs diagnosed with DE/CC condition are put to sleep.
We gratefully acknowledge Flo Sinclair, and her very special Holly Poppet, for her invaluable contributions to the sections of these articles describing Dry Eye/Curly Coat Syndrome in Cavalier King Charles Spaniels. Below is a photo of Holly Poppet, who has DE/CC Syndrome.
KCS in Humans: Dry eyes are common in Sjögren's syndrome, which is thought to be an autoimmune disorder and more common among women than men. Humans with KCS complain of irritation, burning, itching, a pulling sensation, pressure behind the eye, and a feeling as if something is in the eye. They say that symptoms improve during cool, rainy, or foggy weather and in humid places, such as in the shower.
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