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.