Chronic Superficial Keratitis
CSK is a progressive, non-painful inflammatory disease of the cornea and conjunctiva. It affects primarily German Shepherds and German Shepherd crosses, but it has also been reported in other breeds (Siberian Husky, Scotch Collie, Greyhound, Labrador Retriever, Border Collie).
CSK is characterized by variable degrees of corneal vascularization, pigmentation, granulation tissue and cholesterol deposits (white opacities). The corneal changes usually begin at the lower lateral limbus. The disease is bilateral but not always symmetrical. Third eyelid involvement may occur with or without corneal involvement and is referred to as “atypical pannus” or “plasmoma.” The disease is progressive if not controlled with treatment, and can even lead to blindness. There is no cure, and lifelong treatment is necessary with control and vision retention being the goals of therapy.
The cause of CSK is not well understood, but it is known to have a heritable basis. Ultraviolet (UV) radiation plays an important role as an inciting and propagating factor. Dogs living at high altitudes and low latitudes are more severely affected. Flare-ups may be noted during spring months when the sun is closer to Earth. It is an autoimmune disease, meaning the dog’s ocular tissues are inappropriately targeted by the immune system.
The disease is controlled using immunomodulating (cyclosporine, tacrolimus) and anti-inflammatory (steroid or non-steroidal) medications. After disease remission, medications are tapered but never discontinued. Avoiding sunlight (i.e. afternoon shade) is recommended in affected dogs. Some dogs may also benefit from wearing UV-protective “doggles” when outside. Lifelong therapy is necessary, and in dogs diagnosed earlier in life (before 5 years of age) the disease may increase in severity over subsequent years and require more medications than the previous years.