Ophthalmology - Special Services, Technology, & Information
Keratoconjunctivitis Sicca (KCS or "dry eye")
Keratoconjunctivitis sicca (KCS) or "dry eye" is a very common ocular disorder affecting the cornea and conjunctiva. This condition is the result of inadequate tear production. Normal tear production is essential to good ocular "health" and a deficiency in tears can lead to serious and sometimes permanent eye problems. Although untreated KCS can potentially be a blinding disease, it is relatively easy to diagnose and usually responds favorably to long-term medical therapy. Below are some important facts about this disease.
The Tear Film
The tear film covers the outermost surface of the cornea and is essential to ocular “health”. It is produced by various secretory tissues associated with the eye. Although very complex in nature, its main purposes include:
- removing debris from the surface of the cornea,
- providing the cornea with nutrition,
- supplying moisture and lubrication,
- increasing the optical properties of the eye, and
- fighting bacteria.
If untreated, a deficiency of tear film can lead to various ocular disorders. Once the tear film falls below a certain level of production (hence the term dry eye), the conjunctiva and cornea can rapidly become adversely affected. This can be a very painful process and lead to corneal ulceration and pigmentation. This can result in permanent visual impairment or even blindness.
The diagnosis of KCS is based on clinical signs and is confirmed by the results of a quick and simple test to measure tear production. This test is painless, reliable and can be performed in the exam room. Your veterinarian plays a key role in the early recognition and management of this disorder before visual impairment occurs.
Causes of KCS
There are many causes of inadequate tear production. Among the more common include: breed predisposition (inherited), immune mediated disorders (caused by the animal's own immune system), use of certain drugs, and some systemic diseases. Breeds most often affected with KCS include West Highland White Terrier, Bulldog, Cocker Spaniel, Boston Terrier, Lhasa Apso, and Shih Tzu. There is a tendency to see KCS more often in females than males and it usually occurs in middle to older age dogs. We recommend that dogs affected with breed related KCS not be used in breeding programs.
KCS is usually a treatable disease, however, it requires a long-term commitment from the owner. The exact frequency of medication may vary, but often includes the use of a high quality tear film replacement compound or “artificial tears" to mimic the natural tear film. It may be important to instill these drops as often as every two hours in the early course of therapy. These artificial tears are usually used in conjunction with drugs such as Cyclosporin or Tacrolimus. When Cyclosporin is administered topically onto the eye, tear production will significantly improve in about 80% of all cases depending on the cause of KCS. The exact mechanism by which Cyclosporin or Tacrolimus increases tear production is not fully understood. The increase in tear production usually occurs within the first couple of weeks of twice a day therapy. An occasional "late responder” will start to increase tear production within an additional few weeks. Even when tear production returns to normal or near normal limits, therapy must continue for the life of the animal. In certain cases the frequency of artificial tear therapy can be reduced or even discontinued once the full effects of Cyclosporin have been realized. This emphasizes the importance of early recognition of KCS and initiation of proper medical therapy. In many cases, the damage to the cornea and conjunctiva will significantly improve once the tear production is returned to normal.