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Kerato-Conjunctivitis sicca
Sonya J. Miller-Smith

Keratoconjunctivitis sicca, usually abbreviated to KCS, is a condition of the eye, where insufficient tears are produced. The result is an eye that is dry, hence the more common name of ‘Dry Eye’. Although it can affect many domestic species, including cats and horses, KCS is most commonly seen in dogs. In a recent study of dogs with eye problems, an amazing 40% were diagnosed with KCS – so, as you can see, it is a surprisingly common condition. So how can you tell if your pet is affected?

Which dogs get Dry Eye?

Any dog can be affected by KCS, but some breeds are predisposed. These include:

Westies	Yorkshire Terriers
Cocker Spaniels	Jack Russel Terriers
Cavalier King Charles Spaniels	Shit Tzu
Lhasa Apso	Bull Dogs
Labradors	Collies
Springer Spaniels

The condition can occur at any age, but is most commonly seen in dogs of 6 to 10 year of age.

How can I tell if my dog has Dry Eye?

The earliest symptom of Dry Eye is conjunctivitis, or inflammation of the inner eyelids. Frequently, this conjunctivitis seems to respond to antibiotic drops, but quickly returns when the course is finished. As the condition develops, mucous threads may be noticed on the surface of the eye, which move as the dog blinks, or build up at the bottom of the eye, near the lower lid. With time, some of the mucus can build up around the eye, becoming dry and crusty. Owners of affected animals often report how frequently they need to clean their pet’s eyes.

Without proper diagnosis and treatment, the condition progresses to keratitis, inflammation of the cornea or front of the eye. At this stage, the cornea will appear dull and lacklustre. This is particularly noticeable if the dog is turned towards a light bulb or bright window – instead of seeing a clear reflection of the bulb or window, the reflection is indistinct and blurred. Dogs will often show signs of discomfort by squinting and rubbing their eyes, and corneal ulcers are frequently present at this stage.

As the condition progresses, the cornea becomes invaded with blood vessels, scarred and pigmented, leading to reduced vision and eventually blindness. Sadly, these changes are irreversible.

How is KCS diagnosed?

Most cases of KVS have very characteristic symptoms, which may lead you and your vet to be suspicious. However, as these symptoms can resemble simple conjunctivitis, to be sure of KCS, the dog’s tear flow has to be measured.

This is done by the ‘Schirmer Tear Test’, and takes just one minute! It involves placing a standard paper strip between the lower eyelid and the eyeball for 60 seconds, and measuring the distance that the tears move along the strip. If the tears have moved more than 15mm, the dog is definitely normal. If the tears have moved less than 10mm, the dog is definitely abnormal and has KCS. There is a ‘grey area’, of 10-15mm where affected individuals could be either normal or abnormal. In dogs that have very characteristic symptoms, the usual practice is to treat the eye symptomatically, and retest one month later if the symptoms have not subsided.

What causes KCS?

There are a number of possible causes of KCS, these 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), and aspirin.
Viral 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.

How is Dry Eye treated?

Unfortunately, there is no cure for KCS. However, the good news is that the condition can usually be very successfully managed:

MEDICAL TREATMENT

There are two types of long term medical treatment for KCS:

artificial tears, used to wet the eye, and
drugs which are used to stimulate tear production.

1. Artificial tears

These preparations are slightly viscous drops that wet the eye, rather than dropping instantly away like water would. The problem with these artificial tears is that they have to be applied to the eye very frequently to be successful. Typically this means every 2 hours (!!), although more frequently is desirable if it is at all possible. There are a number of brands available, including Viscotears, Hypromellose and Lacrilube.

2. Drugs used to stimulate tear production

Pilocarpine – This drug is given orally to stimulate tear production by the tear glands. It has proved useful when nerve damage is the cause of the KCS, but otherwise is rarely used nowadays.

Cyclosporine A – This drug is marketed in the UK as ‘Optimmune’, and is available as an ointment that is applied to the eye usually twice a day. Cyclosporin A is a powerful suppressor of the immune system, and when applied to the eye acts to prevent the immune system from destroying the tear glands, without effecting the rest of the dog’s immune system. In very advanced cases, where all of the tear glands have been destroyed, this drug is not effective.

Fortunately, Optimmune is usually very successful in managing KCS, and an increase in tear production is usually seen within one month of the start of its use. The only problem with Optimmune is its cost: it is a very expensive drug, retailing at about £30, for a tube that lasts only about 4 – 6 weeks for most dogs i.e. 67p - £1 per day. However, before cyclosporine A became available, there was no really effective medical treatment for KCS. This drug restores natural tear production and is preferable to any other form of treatment, and in the vast majority of cases is the treatment of choice.

SURGICAL TREATMENT

Where KCS is unsuitable for medical treatment, there is a surgical procedure to move the outflow from the salivary glands into the eye, called ‘Parotid Duct Transposition’. Normally the parotid salivary gland empties saliva into the mouth. If this gland is working properly, and has not been affected by the cause of the KCS, this operation can be performed by a specialist eye surgeon. However, there are a number of potential problems with this procedure:

saliva is not a perfect replacement for tears;
saliva flow is much less than tear production;
saliva salt crystals can form in the eye.

For this reason, a Parotid Duct Transposition should not be undertaken lightly, and only after medical treatment has proven unsuccessful.

The outlook for affected dogs

The outlook depends on what the underlying cause is, and how long the dog has been affected with the disease. In dogs that have thyroid hormone deficiencies, the outlook is invariably very good – normal function can be expected to be restored with thyroid hormone tablets.
Most cases of idiopathic, autoimmune or drug-induced KCS will respond tremendously well to cyclosporine A treatment, and as long as it is affordable, it is the mainstay of treatment. Unfortunately, if the disease is very longstanding, the dog may be completely blind due to irreversible changes within the cornea, irrespective of whether or not tear production returns.

If parotid duct transposition is performed, it is important not to forget that the dog still has KCS, and keep to a regime of regulated food intake, to stimulate tear production. If cyclosporine A is unsuccessful, and parotid duct transposition not possible due to a lack of saliva, the only treatment option is very frequently administration of artificial tears, and it is inevitable that these dogs will do less well than those managed by other treatments.

If you are concerned that your dog may have KCS, or even if you want the peace of mind from knowing that he/she doesn't have KCS, contact the practice to book a free Schirmer Tear Test in the nurse's clinic.

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Kerato-Conjunctivitis sicca

Sonya J. Miller-Smith