Alison Laurie-Chalmers, Senior Consultant, Crown Vets Inverness.
Dry eye is a common eye condition in dogs resulting from inadequate production of the aqueous portion of the tear film by the lacrimal gland and/or the third eyelid gland. Usually this affects middle aged to older dogs. Both eyes are usually affected, although one eye may appear worse than the other.
Tears are important and are required to lubricate the cornea and remove any debris or infectious agents that may contact the surface of the eye. Any condition that impairs the ability to produce adequate amounts of tear film can result in 'dry eye'.
Some of the common causes of Dry Eye include:
- Immune-mediated diseases that damage the tear producing glands. This is thought to be an inherited disorder.
- Systemic diseases such as canine distemper virus or feline herpes virus infections
- Some medications such as certain sulphonamide antibiotics (“sulpha” drugs)
Certain breeds are more likely to develop KCS for example: Cocker spaniels, Cavalier King Charles Spaniels, Lhasa Apsos, Miniature schnauzers, Pekingese, Pugs, Shih tzus, West Highland white terriers and Yorkshire terriers.
The symptoms are usually painful, red and irritated eyes. Patients squint, blink excessively or hold their eyes shut. There is often a thick, yellowish, mucoid discharge present as a result of the decreased natural tear film. The eyes often have a duller appearance due to the corneal drying. In chronic cases, there is often a history of recurrent conjunctivitis and corneal ulceration. Some dogs will develop chronic corneal scarring with a dark film covering the eyes often with tiny blood vessels coursing across the corneal surface. Vision may be reduced if this corneal scarring is extensive.
A diagnosis of dry eye is based on clinical signs and decreased tear production tests. The most common tear production test is the "Schirmer tear test". This test uses a special “wicking” paper to measure the amount of tear film produced in one minute. Additional diagnostic tests that may be performed include staining the cornea to check for secondary ulcers.
Treatment has two objectives: to stimulate tear production and to replace the tear film thereby protecting the cornea. There are topical drop medications to achieve this to keep the cornea moist and healthy. Some dogs will also require topical antibiotics or anti-inflammatory medications. Gently cleaning the eyes several times a day with warm water compresses will also help. With today's treatments, the prognosis for dogs diagnosed with dry eye has never been better. This condition does require daily life long medical care, however with diligent attention and regular monitoring most dogs are now able to enjoy a comfortable pain-free life. However, if the condition is diagnosed late in the course of the disease and extensive corneal scarring has already developed then vision will be impaired.
If your dog has recurrent conjunctivitis or any of the symptoms of dry eye, do contact us for an appointment so we can carry out a thorough examination of his eyes.