Pannus is a form of an immune-mediated vascular keratitis that is activated by UV light. It is a highly progressive and potentially blinding disorder, also known as Shepherd Pannus, Uberriter's Syndrome and degenerative pannus. It almost always starts on the lateral side when the cornea is most exposed to light. Although it is thought to be an autoimmune condition in which the body attacks its own cells, it is made worse by exposure to UV light. There is almost certainly a hereditary predisposition to this condition.
Once thought to be confined to Shepherd dogs, the condition sinece has been recognized in other breeds, including the Australian Shepherd, Border Collie, Siberian Husky, Greyhound and Belgian Tervuren.
SIGNS Initially, there is a small corneal opacity with mild inflammation and excessive tearing. Then, a brown patch of pigment, which is reddened by blood vessels, develops on the cornea and gradually progresses toward the center of the cornea. Unless it is aggressively and consistently treated, it will spread over the entire surface within 1 year. Both corneas are usually affected in the same fashion.
TREATMENT There is no cure for this condition, only medical or surgical management and control. Topical corticosteroids, applied over a long period, shrink the corneal blood vessels and stop them from spreading. In cases where corticosteroid treatment cannot be administered, surgical intervention by freezing, heating or excising (cutting out the lesion) is often possible. Research suggests that topical 1% pimecrolimus may be a new effective treatment for keratoconjunctivitis sicca and chronic superficial keratitis in dogs&sa=Search#1400">dogs.
In Shepherds affected at a fairly young age (1-4 years), the condition is usually rapidly progressive and severe. In those animals first affected later in life (4-6 years), the lesions appear to progress more slowly and are less severe. The Greyhounds tend to be affected at younger ages, usually before 2 to 3 uears, but show relatively mild lesions.
Cobblestone" pannus, characterized by rapid advancement of keratitis, appears as red raised areas distributed across the cornea (hence the term "cobblestone").