The lining of the eyelids is called the conjunctiva. When this lining is inflamed, the condition is called conjuctivitis. The signs of conjunctivitis are red, swollen lid tissue and itchy, watery eyes.
The most common cause of conjunctivitis is airborne pollens or other substances to which the dog is allergic. Allergic conjunctivitis often occurs in spring when many molds and pollens are blowing through the air. A dog with this condition often paws at its red, bloodshot eyes, and clear tears may run down its face.
Conjunctivitis can also be caused by a bacterial infection, which can lead to a sticky yellow or greenish discharge from the eyes.
Other causes of conjunctivitis are distichiasis, which occurs when eyelashes grow inward; entropion, a condition in which the eyelids have rolled in; keratitis sicca, a lack of tears; or other eye abnormalities.
Some dogs with cataracts, rickettsial infection or distemper virus can also suffer conjunctivitis.
Foreign bodies lodged in the eye can also cause conjunctivitis. Hunting or other outdoor dogs often will have a weed seed or bit of chaff behind their third eyelids. Whenever the dog blinks, the eye is irritated by these foreign bodies. Dogs with loose, hanging lower lids (a condition called ectropion) are more likely to pick up such irritant as dust, pollen and seeds that can lead to conjunctivitis.
Because conjunctiitis can have so many causes, each case must be diagnosed by a veterinarian so an appropriate treatment can be recommended. To make the diagnosis, the veterinarian will examine the outer eye structures, stain and illuminate the cornea, measure tear production and check the inside of the eye with an ophthalmoscope.
Treatment can range from eye drops for mild allergic or foreign body irritation to surgery for entropion. Most cases of conjunctivitis are easy to treat, but no eye problem should be taken lightly.