Pannus — is also known as Immune-mediated chronic superficial, keratoconjunctivitis (IMCSK). It is a progressive, degenerative disease of the cornea (the front part of the eye you can touch) and the conjunctiva (the pinkish tissue surrounding the cornea). Initially, darkened pigment gathers at the 8 o’clock and 5 o’clock corneal bounderies (limbus). The transparent cornea takes on a light “frosty” or hazy change, followed by increased pigment and blood vessels. If unchecked, the pigment and blood vessels continue to spread over the cornea until they reach the middle, where the 2 fields of pigment seem to mingle. As time progresses, the field of pigment becomes darker, and the abnormal tissue thickens. German Shepherds may also develop multiple thickenings of the outer surface of the third eyelid and the immediate surround tissue, which may occur with or without pannus signs. Pannus usually affects both eyes but not necessarily to the same degree.
The cause of Pannus is still unclear, but UV light is suspected. UV light may alter individual tissue cells to the extent the dog’s immune system does not recognize them as “self” and then attacks those cells as it would a foreign substance. The result is inflammation, which leads to the signs we observe.
The German Shepherd is the most common breed that experiences Pannus. It may occur in other breeds, however, including the Irish Setter and the Beagle.