Dry eye is a condition that occurs spontaneously, to mostly small breed dogs, where the tear production becomes inadequate to keep the eye healthy. The doctor word for this condition is called keratoconjunctivitis sicca. The result is a painful and usually infected eye that appears dull and sticky to the owner. Treatment with medications often will be sufficient to restore normal function to the affected eye.
There are hundreds of tear producing glands in the eyelids of dogs. The gland of the third eyelid can produce as much as 15% of the total tear alone. If a disease or medication or immune system malfunction should destroy enough of the normal tear producing tissue then the cornea will begin to dry out. The cornea is filled with nerve endings and thus having a dry eye is very painful. Without enough lubrication present the normal dust, bacteria, hair, etc. of the world contaminates the eye and can not be washed away. Opportunists such as bacteria will setup an infection in the eye thereby causing conjunctivitis.
If this condition is allowed to exist for a long time there can be permanent damage to the cornea. Ulcers are produced on the cornea as result of the dry eye. Blood vessels that are not normally present on the cornea will appear in an effort to heal the ulcers (neovascularization). Along with the nutrient supply line that is created to heal the ulcers comes pigment. This pigment is deposited on the corneal surface creating a "shadow" like effect. Scar tissue and even occasionally calcium deposits can also contribute to the darkness of the cornea. Potentially, after enough time has gone by, the dog may not be able to see at all out of the affected eye.
An effective tear producing medication is available to return the eye to "normal" if there is enough functional tear glands left. In addition, a broad-spectrum antibiotic salve is necessary to keep secondary bacteria away. While most dogs do very well with this regimen after a few weeks of treatment there are a few that don't respond. For those that don't respond to medical management there is a surgical alternative. A transposition of one of the salivary ducts into the eye works very well in most cases. If your pet will not co-operate for long term medicating the eyes or the owner is either unable or unwilling to medicate often enough, the surgical alternative should be considered.
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