What is Pannus?
Chronic Superficial Keratitis (Pannus) is a disease seen most commonly in the German Shepherds, but does occur in other breeds. A progressive change occurs where blood vessels and scar tissue invade the cornea. This change usually begins in the temporal (outer) or ventral (lower) quadrant of the cornea, and severe cases can involve most or all of the corneal surface area resulting in blindness. With chronicity the affected areas become black with pigmentation.
How is Pannus Treated?
It is believed that Pannus is an immune mediated disease. That is, some subcellular change has occurred in the cornea which the immune system then recognizes as abnormal resulting in an immune mediated attack in the cornea almost as if the cornea was foreign or transplanted tissue. It is suspected that the German Shepherd has a genetic predisposition to this disease, but the damage to the cornea which starts everything is thought to be associated with ultraviolet radiation. The first reports of cases of Pannus came from Austria in the United States – from Colorado, both areas of higher elevation. Today, Pannus is diagnosed worldwide, however it is well recognized that cases of Pannus are more severe and harder to treat in areas of higher elevation, supporting the UV radiation theory. It is hypothesized that dissipation of the ozone layer has resulted in greater exposure to ultraviolet radiation.
It makes sense then to treat Pannus with medications that locally suppress the immune reaction. Steroids (such as dexamethasone and Prednisolone) are anti-inflammatory medications, which provide some immunosupression as a side effect. Cyclosporine, is a drug which has immunosupression as it’s primary mode of action, and applied topically alone or in combination with steroids often results in better control of Pannus than the use of steroid alone.
Cyclosporine has been used by veterinary ophthalmologists in the treatment of Pannus for 12 years now. A 1%, 1.5% or 2% solution is most often used, and was prepared in an oil base-usually olive, corn or vegetable oil. About five years ago a 0.2% cyclosporine ophthalmic ointment called Optimmune (Schering Plough) became available to all veterinary practitioners for the treatment of another eye disorder- keratoconjunctivitis sicca or day eye – where it is quite effective. In pannus cases, however, I find the 0.2% ointment produces less success than the 1% solution. With treatment, the active vascularization and granulation tissue often resolves, but the scarring and pigmentation may improve somewhat slowly or not at all.
A related condition where a similar immune medicated reaction is confined to the conjunctiva and the third eyelid is called PLASMOMA or Plasmacytic Lymphocytic Conjunctivitis of the third eyelid. This variation is also much more common in the German Shepherd. Compared to Pannus, plasmoma is less threatening to the vision, my cause more discomfort, and is somewhat more resistant to the treatment regime which is the same for Pannus.
Reduction of exposure to ultraviolet radiation is also helpful in the longterm control of Pannus. Keeping the dog indoor during the sunniest part of the day; providing a doghouse shelter; or trying a specialty pair of canine sunglasses called RexSpecs may prove very helpful.
Since Pannus is an immune mediated disease, it is managed by treatment but not cured. Ongoing treatment for life is needed to maintain vision.
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