Pannus: Corneal Inflammation in the German Shepherd Dog (German Shepherd Dog Keratitis, Keratitis Ueberreiter)
By Dr. W. Neumann
What is Pannus?
German Shepherd Dog Keratitis [pannus], medical name: keratitis superficialis vasulosa pannosa pigmentosa chronica, is a chronic inflammation of the corneal surface and, in most cases, of the conjunctiva of the eye. In veterinary medicine the disease is also known as Keratitis Ueberreiter, named after the man who first described it (1). The reason it is called German Shepherd Dog Keratitis is because the disease is found predominantly in German Shepherds and is only rarely seen in other breeds (e.g., Collie, Poodle, Dachshund, Greyhound, mixed breeds).
What are the Symptoms of Pannus?
The disease generally manifests itself in dogs between the ages of three and five. It first appears in the outer regions of the cornea and, in almost all cases, affects both eyes simultaneously. Vascular granules and connective tissue establish themselves at the border between the sclera and the cornea, which is often variously pigmented, and grow into the top-most layers of the cornea. This results in the formation of an opaque, cherry-coloured spot with an uneven surface often ringed by a fatty, grayish-white band.
As the disease progresses, pigment forming cells migrate from the outer edges into the afflicted area, giving the spot, which expands toward the center of the cornea, a gray-pink to a variegated brown and black appearance. Frequently there will be a concurrent inflammation dependent reddening of the conjunctiva. Without treatment, the inflammation will progress to cover the entire cornea and can lead to total blindness.
What Causes Pannus?
In the past, discussions centered around infectious agents. Although the precise origins of the disease are still not known in detail, it is now generally accepted to be a derailment of the immune system whereby the organism, in an autoimmune response, produces antibodies or toxic immune cells against its own tissues. At the onset of the disease additional factors are involved: those naturally produced by the body (endogenic), and those which are external (exogenic). The endogenic factor in this context appears to be a breed-dependent inherited predisposition to this disease in the German Shepherd Dog, although the hereditable succession is not known at this time. The predominant exogenic factor is ascribed to ultraviolet rays in sunlight as the trigger of pannus which explains the increased incidence of the disease during sunny months.
What are the Consequences of Pannus?
If the dog does not receive veterinary care, the disease progresses in phases which, based on the above described symptoms, will lead to corneal blindness of the animal in the terminal stage. The cornea loses the transparency required in the mechanism of sight due to pigment deposits. Because pannus generally occurs bilaterally, sooner or later a complete loss of sight must be expected.
How Does the Veterinarian Treat Pannus?
Recovery, in the sense of curing the disease, is not possible given the current scientific knowledge. Hence, treatment goals address controlling the active phases as quickly as possible, avoiding further outbreaks, and minimizing the described consequences of the disease.
Because, as mentioned above, pannus is based on a "malfunction" of the body's immune system, local applications of cortisone can suppress a flare-up. During an acute phase of the disease these are administered by the veterinarian via injections under the conjunctiva of the affected eye. Prior to this procedure, the eye is treated with a local anesthetic applied with drops to the surface of the eye so that the dog does not feel pain during the subsequent injection.
At home, the owner of the animal continues cortisone therapy with an ointment which must initially be applied several times per day (4-5 times). Later this therapy, in conjunction with regular examinations by the veterinarian, can be phased down, but a daily maintenance dose must be continued over the life time of the dog. An alternative treatment is the topical application of a cyclosporin containing ointment for the long-term management of the disease (2).
In hopelessly protracted cases, or in cases where the disease can no longer be controlled with medication and has caused blindness in the animal, surgical removal of the affected top layers of the cornea is possible. However, because this relatively grave procedure cannot be repeated indefinitely and because surgery does not present a causal cure for the disease, this method should be reserved strictly as a final effort in most severely advanced cases.
What Can the Dog's Owner Do?
In addition to conscientious adherence to the long term treatments prescribed by the veterinarian, regular visits to and examinations by the treating veterinarian, and an immediate (!) consultation with the veterinarian when there is a new occurrence of acute disease symptoms, the patient should be isolated from all factors which trigger the outbreak of the disease.
There is considerable evidence that the short wavelengths of the sun's rays play a major role in the emergence of an acute phase of the disease. Hence, the eyes of an affected dog should be protected from extended exposure to UV light. This includes bright sun on a cloudless day; snow cover, especially at high altitudes and in bright sun; and sunshine during times spent on or near bodies of water.
This means that on days where increased UV exposure is anticipated, dogs should only be walked in the early morning hours, in the evening, or in forested areas, and otherwise should be kept indoors or at locations not subject to direct sun exposure (i.e., in the shade).
If for various reasons UV exposure to the dog cannot be avoided, the animal's eyes must be protected throughout the duration of exposure. This can be accomplished with either specially fitted sun glasses which are, after a short adjustment period, accepted without problems by many dogs, or with the administration of drops containing a UV blocking agent into the conjunctival sacs of the eye. The relatively short term effectiveness of the latter measure requires that the medication be reapplied at specific intervals (approximately hourly).
Copyright and Translation Information
Copyright: Dr. W. Neumann, Clinic of Veterinary Surgery, University of Giessen 35392 Giessen, Germany. (Reproduction in full or part allowed only with permission of the author.)
(1) Prof. Ueberreiter, Vienna, Austria
(2) Added by request of the author. See also Chronic Superficial Keratitis: Results of a European Controlled Study of Cyclosporin Ophthalmic Ointment by Dr. Neumann, published in Proceedings of ESVO/ECVO Meeting in Dresden, Germany, 1994 (Published by Schering Plough, USA).
Translated with permission of the author by Anka Andrews, Science Translations. Translation copyright: Anka Andrews, 1996 .