A healthy cornea and conjunctiva at the front of the eye is highly dependent on the presence of a healthy tear film. The normal tear film is made up of three layers:
- The outer lipid layer produced by the Meibomian glands within the eyelids.
- The aqueous (watery) layer. This represents over 95% of total corneal thickness, The watery component of the tear film is produced by lacrimal gland, a small gland which is found deep in the tissues behind the outer upper eyelid.
- The mucous layer. This layer enables the tear film to “stick down” to the surface corneal cells.
There are many causes of dry eye including congenital disorders (puppies), infections (canine distemper virus), drug-induced (sulfa antibiotics), and removal of the tear gland of the third eyelid ("cherry eye"). The most common cause is thought to be autoimmune destruction of the lacrimal gland by immune system cells: the immune system inappropriately attacks the cells in the gland which produce the watery component of the tear film. The disease is seen very commonly in certain breeds such as the Cocker Spaniel, Shih Tzu, Lhasa Apso, Bulldog, Schnauzer, and West highland White Terrier.
Clinical signs of dry eye
The clinical signs of dry eye include:
- heavy mucus production
- rubbing at eyes
- cloudy eyes
- corneal ulcers
- general lethargy
Many dogs have a history of having been treated for recurrent “conjunctivitis” with various anti inflammatory/antibiotic ointments or drops. After an extended period of dryness, the surface of the eye (cornea) begins to accumulate dark scar tissue and blood vessels – unfortunately to the point of blindness in many patients.
Our treatment goals for dry eye include stimulation of tears, lubrication, and decreasing the scar tissue. In the past few years we have had a major breakthrough in the treatment of this disease with the development of the drug Cyclosporine. This drug is about 75% effective in stimulating new tears in the dog; we never had any drug like this before! Cyclosporine HAS to be used absolutely as directed. If you skip a dose or run out of the medication, they dry eye signs will immediately recur. In addition, it is crucial that you have your dog checked as directed to monitor treatment success.