At a recheck examination three weeks later, the dog's corneas were completely clear except for several superficial ghost vessels
in each eye that were visible with the biomicroscope and some corneal cloudiness due to scarring. We continued the dog's medications
at the same dosage and scheduled another recheck for six months later.
CSK is also called pannus, German shepherd pannus, degenerative pannus, and Uberreiter's syndrome. It was first described in 19131 and further characterized in 1959.2 This progressive degenerative disease involving the subepithelial portions of the canine cornea is characterized by bilateral,
fleshy-looking lesions that initially appear at the temporal limbus and then spread nasally toward the central cornea. If
the disease is left untreated, lesions also arise from the nasal limbus and progress laterally, joining the laterally arising
lesions. In its early stages, the disease may be difficult for owners to recognize. As it progresses, superficial vascularization
may be intense and large vessels may appear. Limbal melanocytes, if present, also invade the subepithelial cornea, making
the lesions appear black (Figure 3). Pigment can appear in the disease's early stages if the limbus is heavily pigmented. This can make it even more difficult
for some owners to detect a problem because from a distance the eye appears dark, as it normally would in most dogs. In fact,
owners may detect visual deficits before they notice the corneal lesions. The superior portion of the cornea is the last area
to be affected, and eventually, the entire cornea may be pigmented, vascularized, and scarred (Figure 4). Frequently, small white dots or a white line in the cornea may precede the advancing fleshy lesion (Figure 2).3 In some dogs, thickening and depigmentation of the nictitating membrane may occur concurrently with or independently of the
corneal lesions.3 This is called atypical pannus or plasmoma (Figure 5).
FIGURE 3. Pigmented CSK in a German shepherd. Note that the lesion originates from the lateral limbus. FIGURE 4. An advanced
case of pigmented CSK in a German shepherd. The eyelid speculum has been placed in preparation for the dog radiation therapy.
FIGURE 5. Atypical pannus, or plasmoma, in a German shepherd. The nictitating membrane is depigmented, thickened, and irregular.
Two predisposing factors to developing CSK are known. One of these factors is breed of dog. German shepherds are overrepresented,
but other breeds frequently affected include greyhounds, Belgian Tervurens, dalmatians, dachshunds, and Siberian huskies.4 No specific genetic mutation leading to this disease is known of, but the disease tends to be familial. Exposure of the cornea
to ultraviolet light is another predisposing factor. Both the incidence and severity of CSK increase with increasing altitudes,4,5 and dogs living at lower elevations respond more favorably to therapy than dogs living at elevations over 4,000 ft do.5