We’re considering the most common eye diseases of pets and cats, and have discussed red eyes (conjunctivitis) and ulcers (keratitis). These are both problems that tend to be sudden and short lived. Let’s consider a problem that is not acute, but chronic: Dry Eye. Dry eye is also called KCS or Keratoconjunctivitis Sicca.
• Dry eye is a serious medical problem that usually requires treatment for life.
• Some breeds are genetically prone to develop dry eye.
• Some antibiotics and pain medications cause dry eye.
What causes dry eye?
Dry eye is caused by
• infection, such as distemper
• trauma that damages the tear-producing glands
• a faulty immune system that attacks the body’s own tear-producing glands
• prescription drugs and wormers, and
• genetic tendencies.
Not enough tears
Dry eye occurs when pets don’t make watery tears. Instead of being wet enough to flush the eyes, tears are thick and mucoid. They collect in clumps and stick on the inner and outer corners of the eyes. Dirt is not washed away by tears, and it collects on the eye and scratches the cornea.
What are tears?
Tears may look like simple drops of water, but they are much more complex. Tears have three parts, an oily layer to help tears slide over the eye, an inner mucin or mucoid layer that helps tears coat the eye, and the watery or aqueous layer. About 85% of tears are the watery layer. With dry eye, the watery portion of the tear isn’t made. Because the mucoid portion of tears continues to be made, a thick discharge collects in the eyes. When we see this mucus, it’s easy to think a pet has sleep in its eye, or, perhaps a slight infection. A Schirmer tear test shows whether or not the mucus is caused by dry eye.
In a future blog, we’ll continue discussing dry eye, including breeds predisposed to develop dry eye andsome of the medications that actually increase the likelihood that dry eye will occur.
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