The most prevalent form of pannus affects the cornea; the precise medical term is “chronic superficial keratitis.” Pannus is the result of a local inflammatory response initiated by the body’s own immune system. It begins within the conjunctiva, the pink tissue surrounding the eye and inner eyelids. With time, this inflammation extends onto the clear surface of the eye (the cornea), and can eventually result in enough cloudiness to cause loss of vision. On a cellular level, the inflammation is composed of brown melanin pigment, red blood vessels, and grey/pink scar tissue. Sometimes white crystals (cholesterol and calcium) will deposit in the cornea as well.
Factors that contribute to the development of Pannus include heredity and ultraviolet light exposure. The German Shepherd Dog is highly predisposed, which indicates the condition is probably inherited. The Greyhound and other Shepherd breeds including the Belgian Tervuran are also affected more than the average population. Animals living in hot climates, at higher elevations, or near water have additional UV exposure, resulting in an increased incidence of Pannus, which may also be more difficult to control in these areas. The influence of elevation is minimal in the San Francisco Bay Area; however, limiting sunlight exposure may help slow progression of the disease. Some people have had some success in getting their dogs to wear protective visors or goggles when out of doors (only supervised use is recommended).
The mainstay of treatment for Pannus is the routine application of topical anti-inflammatory medications, including steroids, cyclosporine, and/or tacrolimus. These drugs suppress the immune system locally to the eye. Treatment is initially aimed at reversing as much of the corneal changes as possible. Improvement from initial diagnosis is often dramatic, but rarely complete. Then, a long-term maintenance regimen is continued aimed at maintaining control of the condition and best possible vision for your pet’s lifetime. It is important to realize that the condition can be controlled, but cannot be cured. Systemic side effects are rare since the medication is used only in the eye and is minimally absorbed into the circulation. Close monitoring and regular ophthalmic exams are important to maintaining control of Pannus since medication regimens often need to be altered over time.