Keratoconjunctivitis sicca (KCS) - "dry eye"

What is ... ?: 

 KCS or "dry eye" 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 ... inherited?: 

The mode of inheritance is not known.

What does ... 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 ... 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. 

How is ... 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.

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.

Breeding advice: 

 Affected dogs should not be used for breeding.



 Salisbury, M.A. 1995. Keratoconjuctivitis sicca. In J.D. Bonagura and R.W. Kirk (eds.) Kirk's Current Veterinary Therapy XII Small Animal Practice. p. 1231-1239. W.B. Saunders Co., Toronto.

What breeds are affected by ... ?