Chronic superficial keratitis (pannus)
Chronic superficial keratitis
(CSK), also known as pannus or Uberreiter’s
disease, is an inflammatory condition of the cornea
in dogs, particularly seen in the German Shepherd
Chronic superficial keratitis is most commonly seen
in German Shepherd Dogs, but it is also found
in Belgian Tervurens, Greyhounds, Siberian Huskies,
Australian Shepherds, and Border Collies.
CSK is immune-mediated in nature, characterized
by an infiltration of white blood cells into the
superficial stroma of the cornea. These cells are
predominately CD4-expressing T lymphocytes and to
a lesser extent CD8-expressing T cells. The CD4-expressing
T-cells secrete gamma interferon, which causes expression
of the major histocompatibility complex class II
molecules in the cells of the cornea. These class
II molecules cause further inflammation by interacting
with the T cells and triggering an immune response.
Ultraviolet light is important in the genesis of
the disease which is seen at higher prevalence at
elevated altitude and has a seasonal variation with
most cases occurring in the summer. There is likely
also a genetic component to the cause of CSK due
to its predominance in certain breeds.
Signs and symptoms
CSK is usually a bilateral progressive condition.
Signs include pigmentation and vascularization of
the cornea (extension of blood vessels onto the
cornea). It is usually first seen at the lateral
(temporal) limbus (the junction between the cornea
and sclera), although it eventually can extend from
any part of the limbus to cover the entire cornea.
Severe cases can cause blindness. Although CSK is
usually identifiable by the appearance of the eye
and the breed of the affected dog, cytology will
reveal the presence of lymphocytes and plasma cells.
Treatment of CSK is usually with topical corticosteroids
or topical cyclosporine, but any treatment only
controls and reduces the inflammation rather than
providing a cure. Other investigated treatments
include pimecrolimus, a derivative of ascomycin
that interferes with T cell activation and inhibits
the production of inflammatory cytokines. Strontium-90
radiation therapy is also used to treat CSK. Canine
sunglasses have also been used to help protect the
eyes of dogs with CSK to prevent further damage
from ultraviolet radiation.