Keratoconjunctivitus Sicca (KCS) or Dry Eye

Description & Cause
“Kerato” refers to the cornea or clear covering of the eye that faces the outside world. “Conjunctivae” are the moist pink membranes of the eye socket. “It is” means inflammation and “sicca” means dry. KCS means inflamed, dry cornea and conjunctiva. It occurs when there is a deficiency in the water portion of the tear film which normally accounts for 95% of the tear volume. Without the water, one is left with oil and mucus; hence, the gooey yellow eye discharge characteristic of this condition.

Dry Eye describes describes the changes in the eye which result from lack of tear production.There are many causes of dry eye. The most common cause of KCS appears to be that the lacrimal (tear-producing) gland is be gradually destroyed by the dog’s own immune system so that it is no longer able to produce tears. Other causes of dry eye include damage to the nerve supply to the gland and severe conjunctivitis.

There are several forms of the dry eye syndrome. These include
- Partial dry eye that results from a slight reduction of tear production.
- Intermittent dry eye is the result of temporary loss of tear production followed by periods of normal production.
- Complete dry eye is the complete absence of tear secretion.
- Temporary dry eye is the short term loss of tear production due to a variety of causes such as anesthesia.


Symptoms/Clinical Signs
A lack of tears leads to an inflammatory reaction on the surface of the eye. This causes discomfort, sticky ocular discharge, clouding and scarring of the cornea, and eventually blindness if the disease process is not controlled. The process can be slow and insidious and may affect one or both eyes.


Diagnosis
The Schirmer Test is a quick, easy and reliable test for "Dry Eye". This test is done prior to any topical medications or manipulation of the eyelids. Topical Anesthesia is not used to perform the standardized Schirmer Test. The rounded notched end of the sterile test strip is hooked over the lower eyelid and left for 60 seconds then the length of the stip's moistened area is measured.

Schirmer Test Values In Dogs;
Normal: 15-25 mm/min
Borderline: 10-15 mm/min
Below Normal: less than 10 mm/min


Treatment & Prognosis
Treatment is generally directed at reducing any process of “self-destruction” and promoting tear production rather than completely curing the disease itself. For this reason, it is not uncommon for dogs to require life-long treatment.


Inheritance
KCS does seem to have a genetic basis, but the mode of transmission is unknown. One major drawback of preventing KCS is that it is often not apparent until a dog has finished his or her breeding career.