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KCS or "dryeye" is
an eye disease caused by abnormal tear production. The lacrimal
glands produce the watery secretions that make up the bulk
of the tears. A deficiency in this secretion causes KCS in
small animals.
Normal tears are essential for the health and transparency
of the cornea (the surface of the eye). Tears cleanse and
lubricate the cornea, carry nutrients, and play a role in
the control of infection and in healing. Deficient tear production
as in KCS causes chronic irritation of the cornea and conjunctiva.
Corneal ulcers and eventually corneal scarring occur, and
blindness can result.
 There
is a predisposition to this condition in some breeds as listed
below. KCS can also occur in any breed as a result of viral
infection, inflammation, drug-related toxicity, or immune-mediated
disease. There is an association between removal of a prolapsed
nictitans gland ("cherry eye") and the development of KCS.
How is KCS inherited?
The mode of inheritance is not known.
What breeds are affected by KCS?
There is a predisposition to the development of KCS in the
bloodhound, Boston terrier, bull terrier, English bulldog,
English and American cocker spaniel, Kerry blue terrier, Lhasa
apso, miniature poodle, miniature schnauzer, Pekingese, pug,
Sealyham terrier, Shih tzu, standard schnauzer, West Highland
white terrier, Yorkshire terrier
Congenital KCS (ie. the dog is born with the condition) is
rare. It may be one-sided and has been seen in toy breeds
such as the Yorkshire terrier, pug, Pekingese, and Chihuahua.
These dogs have very small or absent tear-producing (lacrimal)
glands.
For many breeds and many disorders, the studies to determine
the mode of inheritance or the frequency in the breed have
not been carried out, or are inconclusive. We have listed
breeds for which there is a consensus among those investigating
in this field and among veterinary practitioners, that the
condition is significant in this breed.
What does KCS mean to your dog & you?
KCS may develop very quickly or more slowly, in one or both
eyes. Commonly it is diagnosed in 1 eye first and develops
in the other eye within several months. The extent of discomfort
depends on the severity of the tear deficiency and how long
it has been present. People with KCS say it feels like they
have sand paper under their eyelids with every blink. Dogs
show their discomfort by rubbing their eyes, squinting, and
being sensitive to light. Your dog's eye(s) may be reddened
and inflamed, or the cornea may appear dull and dry. There
is commonly a thick mucousy discharge in the eye or in the
area around the eye.
Problems associated with KCS include chronic or recurring
irritation or infection of the conjunctiva and cornea, and
corneal ulcers. These conditions are painful and, if KCS is
untreated, over the long term the normally transparent cornea
becomes thickened and scarred. Blood vessels and pigmented
cells move in to the cornea because of the chronic inflammation,
and blindness may result.
How is KCS diagnosed?
Your veterinarian may suspect KCS based on the kinds of clinical
signs mentioned above, particularly in a breed with a predisposition
to this disorder. KCS is confirmed by measuring your dog's
tear production. Your veterinarian will also perform a fluoroscein
dye test to check for corneal ulceration.
FOR THE VETERINARIAN: A Schirmer tear test (STT) should be performed before the use of any drops or ointments in any dog presenting with ocular discharge, irritation, or corneal lesions. Normal STT values in the dog are 15 to 25 mm/minute. Dogs with exposed corneas due to conformation require relatively more tears so may show KCS even with marginal deficiencies.
How is KCS treated?
The goals of treatment are to restore moisture to the eye and to treat conditions such as infection or ulceration that develop because of the lack of normal tears.
Tear stimulants and artificial tear replacements are used to treat KCS. Generally it will take a period of trial-and-error for your veterinarian to determine what is best for your dog. A response to tear stimulants may not occur for a few weeks or even longer, and during this time artificial tears must be used as well. Once tear production has been established, often the use of a tear stimulant once daily, or sometimes once every 2 days, will be sufficient to control KCS.
It is important to recognize that this treatment is not a cure for KCS but rather a way to manage a frustrating, painful, and potentially blinding condition. Clinical signs will slowly return If treatment is stopped.
When medical therapy as outlined above is unsuccessful, surgery can be done to transport one of the salivary ducts to provide moisture to the eye. This is generally less satisfactory.
FOR THE VETERINARIAN: Cyclosporine is the treatment of choice due to its efficiency at stimulating tear production, the need for fewer applications, and the lack of undesirable side effects with long term use. The time required to achieve sufficient tear production varies; usually a response is seen within a few weeks but several weeks may be required. Artificial tears should be supplied until tear production is established.
Breeding advice
Affected dogs should not be used for breeding.
Canine Inherited Disorders Database
* Keratoconjunctivitis sicca (KCS) is due to an aqueous tear deficiency and usually results in persistent, mucopurulent conjunctivitis and corneal ulceration and scarring. KCS occurs in dogs, cats, and horses. In dogs, it is often associated with an autoimmune dacryoadenitis of both the lacrimal and nictitans glands. Distemper infection, chronic sulfonamide therapy, and trauma are less frequent causes of KCS in dogs. KCS occurs infrequently in cats and has been associated with chronic feline herpesvirus infections. In horses, KCS may follow head trauma. Topical therapy consists of artificial tears and, if there is no corneal ulceration, antibiotic-corticosteroid combinations. Lacrimogenics such as topical cyclosporin A (1-2%, b.i.d.) may increase tear production in some dogs. Ophthalmic pilocarpine mixed in food may be useful (a 20-30 lb [10-15 kg] dog should be started on 2-4 drops of 2% pilocarpine, b.i.d.). Mucolytic agents (eg, 10% acetylcysteine) lyse excess mucus and restore the spreading ability of other topical agents. In chronic KCS refractory to medical therapy, parotid duct transplantation is indicated.
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