Keratoconjunctivitis sicca (KCS)
Keratoconjunctivitis sicca (KCS) or Dry Eye is a condition in dogs where the tear production in one or both eyes is reduced. The tears form a protective film over the surface of the eye so if the tear production is reduced, this film becomes compromised and damage to the eye occurs.
The clear surface to the eye, the cornea, is usually kept well hydrated but in KCS, due to a lack of tears, it dries out and becomes inflamed as a result. Affected animals will have red and swollen conjunctiva, called conjunctivitis and often and thick, yellow-green discharge from the eye. Ulceration of the cornea is common and this may cause the usually transparent cornea to look cloudy and opaque. The animal may blink frequently, called blephrospasm, and hold the eye closed or squint as these are signs of a painful eye.
The most common cause of KCS is immune mediated. This means that the animal's immune system is attacking and destroying the glands of the eye that produce the tears, the lacrimal glands. This is not the only cause however and there are many other things that may predispose your dog to KCS.
Some breeds of dog show a predisposition to developing KCS which is likely due to genetic factors. Predisposed breeds include;
Clinical signs will arouse the vet's suspicion of KCS and then a diagnosis is made using the Schirmer Tear Test (STT). The STT comprises of two strips of blotting type paper, one for each eye. One end is folded over and hooked over the eyelid. The paper is left in place for one minute to absorb the tears. After that time the tear production is measured via a scale printed on the paper strips. The tears will also have picked up a dye placed at the beginning of the strip to make the reading clearer. A low reading on this test strip confirms KCS.
If there is an underlying cause, such as hypothyroidism, then treating this cause is likely to reverse the dry eye. If the dry eye is caused by a drug reaction or is immune mediated then it is not reversible and will require lifelong treatment. There are a number of medications that may help to control the condition depending on your dog's particular set of clinical signs and the exact treatment regime will be decided by your vet.
Lacrostimulants: These are products that will stimulate the tear production. The most effective is Optimmune, an ointment containing cyclosporine. Optimunne is usually applied to the affected eye twice daily initially and may take 6-8 weeks to show results. If the treat production increases and the KCS improved then Optimunne can be applied once or twice daily as maintenance therapy throughout life.
Lacromimetics: These are products that mimic or replace normal tears. Examples of these products are Viscotears, Lubrithal and Lacrilube. They have to be applied to the eyes regularly, usually four times a day. They are helpful in long term control of KCS and can be used in conjunction with Optimmune.
Antibiotics and Anti-inflammatories: These may be needed if the KCS is complicated by secondary infection or if the eye is swollen or painful. These may be given topically, as additional ointments in the eye or orally as tablets or liquid in the food.
Also see our Optimmune article.