Pannus is a term used to describe a specific type of corneal inflammation; the precise medical term is “chronic superficial keratitis”. Pannus is caused by a local inflammatory response initiated by the body’s 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 cause cloudiness resulting in vision loss. On a cellular level, the inflammation is composed of brown melanin pigment, red blood vessels, and pink scar tissue. Sometimes white crystals (cholesterol and calcium) will deposit in the cornea as well.
There are several factors that contribute to Pannus, the most significant of which is breed. The German Shepherd dog is highly predisposed, which indicates the condition is probably inherited. Other breeds can be affected, in particular the Greyhound and other Shepherd breeds including the Belgian Tervuran. Another contributing factor is exposure to sunlight or ultraviolet radiation. Animals living at higher elevations or near water have additional UV exposure and, in such situations, the pannus condition may become worse. 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.
The mainstay of treatment for pannus is topical anti-inflammatory medication, the most effective of which are steroids and cyclosporine. These drugs suppress the immune system local to the eye. These drugs must be used long term and usually for life. Although side effects are rare, close monitoring and regular ophthalmic exams are important. Systemic side effects are extremely rare since the medication is used only in the eye and is minimally absorbed.