‘Dry eye’ (Keratoconjunctivitis sicca)

Keratoconjunctivitis sicca (KCS or ‘dry eye’) develops when insufficient tears are produced from the tear glands. Tears keep the surface of the eye moist, help to flush away surface debris (such as dust landing on the cornea), provide lubrication to aid blinking, and have antibacterial properties to fight infections. Reduced tear production may affect all of these important functions. Over a period of time, affected eyes may become blind due to scarring and pigmentation of the cornea.

The most common cause in dogs is when the body’s own immune system attacks the tear glands, which are then gradually destroyed over a period of months or years. What exactly triggers this attack to make some dogs develop KCS is unknown.

Usually both eyes are affected, although sometimes to different degrees. Clinical signs include the following:

• Conjunctivitis, which may respond to antibiotic treatment but has a tendency to recur.
• A sticky grey discharge from the eyes (this discharge may turn white, yellow or green if it becomes infected).
• Clouding or dullness of the cornea.
• Discomfort around the eyes – the animal may blink more than normal or rub at its eyes.

KCS is diagnosed by performing a Schirmer tear test. This simply involves placing a strip of filter paper against the cornea and measuring the degree of wetting over the course of 1 minute. The Schirmer tear test is quick and easy to perform, and well tolerated by the patient.

Your vet will be able to give you something to help your pet if they have dry eyes. The aims of treatment are to keep the eyes comfortable and to minimise the scarring and pigmentation caused by KCS, which may lead to blindness if left untreated. Most cases of KCS will need lifelong management. Treatments will vary from case to case.

Medication to stimulate tear production

In most cases, the first-line treatment is ciclosporin 0.2% eye ointment (Optimmune™). This treats the underlying cause of KCS by reducing the immune system attack on the tear glands. For optimal results there must be some residual tear gland function, so this treatment works best in mild to moderate cases. It is usually very effective, but treatment must be given twice daily every day, and lifelong treatment is usually required. If Optimmune™ fails to work, then in some cases other similar types of drug may prove effective (for example ciclosporin 1% solution or tacrolimus).

Lubricants/ artificial tears

Various types are available. These include drops, gels and ointments to keep the surface of the eye moist and prevent evaporation of tears. These do not treat the underlying cause, but instead help to replace the tears that are not being produced. They are often used in conjunction with Optimmune™.

Antibiotics

Corneal ulcers and bacterial infections occur quite commonly in dogs affected with KCS and so a course of antibiotic eye drops may be prescribed from time to time.

Surgery

Parotid duct transposition (PDT) can be performed if the above treatment proves ineffective. This surgery involves relocating a duct of one of the salivary glands from its usual opening into the mouth to inside the lower eyelid. Saliva is then secreted onto the surface of the eye and acts to keep the surface of the eye moist.

In many cases, this proves a very effective treatment. However, saliva is not exactly the same as tears, so in a few cases it may cause problems such as irritation to the surface of the eye or to the skin around the eye. For this reason, PDT is usually reserved as a last resort should medical management fail.

Whatever treatment is recommended, lifelong management will usually be needed and regular visits to your vet will be required in order to monitor tear production and ensure that the eye is responding successfully to treatment.