What causes dry eye?

There are a number of potential factors that can cause dry eye including infection, trauma, reaction to medication and problems with the nerve supply to the tear gland. However, the most common cause of dry eye is due to destruction of the tear gland by the animal’s own immune system.

A Schirmer tear test (STT) is used to diagnose dry eye which is quick and easy to perform.

Clinical signs

• Recurrent conjunctivitis
• A sticky discharge from the eye
• Clouding or dullness of the cornea
• Discomfort – excessive blinking or rubbing the eye
• Corneal ulcers

Treatment options

The main aim of treatment for keratoconjunctivitis is to keep the eyes comfortable, free from infection and to preserve vision by increasing tear production. The first line of treatment is usually OptimmuneTM, a topical eye ointment that treats the underlying cause of dry eye (prevents the immune-mediated destruction of the tear glands) and directly promotes normal tear production. If your pet doesn’t respond to Optimmune, there are alternative drops available such as Tacrolimus, that also stimulates tear production. Both medications are usually lifelong.

It normally takes around 4 weeks for these drops to work so artificial tears are likely to be prescribed in conjunction with these medications to soothe and lubricate the eye until the body is making enough tears for itself.

Cleaning the eyes and eyelids regularly with cooled boiled water can reduce the risk of skin infections and keep your pet comfortable.

Surgical options

A surgical procedure can be performed to redirect a small quantity of saliva from the mouth onto the surface of the eye. This surgery is called a parotid duct transposition (PDT) and is carried out under a general anaesthetic. The transposed salivary duct is moved from the inside of the cheek towards the eye and small stitches are used to fix the duct in place.

Unfortunately, saliva does not have the same composition as tears and small crystals can develop on the surface of the eye. Excessive wetting around the eyes may also be seen and some cases may still require lifelong eye drops.