Content
- Keratoconjunctivitis Sicca in the Dog
- What are the Symptoms of KCS?
- How is KCS Diagnosed?
- What is the Cause of KCS?
- How is KCS Treated?
- Outlook for Affected Dogs
What is Keratoconjunctivitis Sicca?
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 its common name of “Dry Eye.”
When you look at an eye, you see the eyelids, cornea (the see-through part), and the sclera (the white part). The coloured part of the eye is the iris, a muscular sheet that lies behind the cornea and in front of the lens. The cornea is completely clear in the normal dog lacking any blood vessels or pigment. This means any cells within the cornea have to derive their nourishment from one of two sources:
- The aqueous humor (the water behind the eye), which is constantly being produced and absorbed.
- Tears, which contain water, lipid (oil), and mucus.
In KCS, it is only the water component that is deficient.
What are the Symptoms of KCS?
The symptoms of KCS are due entirely to the consequences of having insufficient tears, and the resultant drying of the cornea.
In the early stages, the conjunctiva appears red, the eye is acutely painful, and there may be spasm of the eyelids. Later, pain diminishes, leaving irritation. A thick, sticky, yellow discharge is common, which often relapses after treatment if misdiagnosed as conjunctivitis.
The cornea becomes dull and lacklustre, then invaded by blood vessels and pigment, reducing light passage and causing potential blindness. Painful corneal ulcers may also occur.
Breeds predisposed to KCS include:
- West Highland White Terrier
- Cavalier King Charles Spaniel
- Yorkshire Terrier
- Lhasa Apso
- Cocker Spaniel
- Shih Tzu
- Bulldog
How is KCS Diagnosed?
Most cases have characteristic symptoms, but to confirm KCS, the Schirmer Tear Test is performed. A paper strip is placed between the lower eyelid and eyeball for one minute:
- >15mm: Normal
- <10mm: Abnormal
- 10–15mm: Grey area (uncertain)
What is the Cause of KCS?
Causes of KCS include:
- Autoimmune disease
- Drug reaction (e.g. sulphonamides, aspirin)
- Congenital defects
- Idiopathic causes
- Viral infections (e.g. Distemper)
- Nerve supply failure to tear glands
- Thyroid hormone deficiency
Common sulphonamide drugs linked to KCS:
- Tribrissen®
- Duphatrim®
- Norodine®
- Trimacare®
- Sulphasalazine (Salazopyrin®)
How is KCS Treated?
Initial Medical Treatment
Early cases require lubrication, antibiotics, and sometimes steroids to reduce blood vessel growth. Maxitrol® drops (hypromellose + antibiotics + steroid) are commonly used at Vetrica (not licensed in dogs, except with ulcers).
Long-Term Medical Treatment
- Artificial Tears – frequent application (every 2 hrs); provides lubrication but not full tear function.
- Pilocarpine – stimulates tear glands if nerve supply is affected; limited use in most cases.
- Cyclosporine A (Optimmune®) – preferred treatment; restores natural tear production in autoimmune or drug-induced KCS.
Surgical Treatment
In refractory cases, Parotid Duct Transposition moves a salivary gland duct into the eye. This is complex and only used when medical treatment fails.
Outlook for Affected Dogs
Prognosis depends on the cause and duration of the disease:
- Thyroid hormone deficiency → excellent outlook with tablets
- Idiopathic, autoimmune, or drug-induced KCS → very good with cyclosporin A
- Advanced cases → possible blindness due to corneal damage
- Parotid duct transposition → useful in selected cases but still requires management
