Pannus - chronic superficial keratitis
Pannus, or chronic superficial keratitis, is a condition of ongoing inflammation of the cornea (the surface of the eye). Pannus begins as a grayish haze. Gradually blood vessels and pigmented cells move into the normally transparent cornea. As the inflammatory changes spread across the cornea, vision is affected. The condition gradually worsens and usually affects both eyes.
In atypical pannus, the third eyelid is affected rather than the cornea. This is most common in German shepherds.
Pannus appears to be caused by an inappropriate response of the immune system. It occurs more frequently and is harder to control in dogs that live at high altitudes and/or are exposed to increased levels of ultraviolet radiation.
The mode of inheritance is unknown.
If untreated, the blood vessels and inflammatory cells will spread over your dog's normally transparent cornea, gradually darkening and scarring it, and causing visual impairment. This can occur slowly over months or years, or it can occur rapidly to involve the whole cornea within a few months. The condition does not appear to be painful.
Lifelong treatment is required to control this disorder (see below). Usually pannus can be well-controlled, although it is harder to control in dogs living at high altitudes (above 1500 metres). Sometimes lesions will worsen in periods of environmental irritation or increased ultraviolet exposure, or if medication is given irregularly.
Diagnosis is made based on the signalment (breed and history) and the typical changes in your dog's cornea.
Usually pannus can be well-controlled. However treatment must be lifelong and consistent, or the lesions will return and worsen.
The goal of treatment is to prevent vision loss, or to return as much vision as possible if there is loss. This is done with the use of anti-inflammatory drops in the eye. Drugs used alone or in combination include corticosteroids and cyclosporin A. Your veterinarian will make specific treatment recommendations based on the severity of the changes to your dog's eyes, and the response to therapy. Usually therapy begins with 4 treatments a day. As the size of the area affected decreases, treatments will be decreased to the lowest frequency that controls the condition.
Once effective treatment is established, your veterinarian will evaluate any changes once or twice a year, or if you notice a worsening of the condition as may occur in periods of environmental irritation or increased ultraviolet exposure.
You will see bilateral lesions consisting of vascularization, pigmentation, or a combination - usually starting in the temporal or inferiotemporal quadrant and progressing centrally. Atypical pannus may affect the nictitating membrane without affecting the cornea. The leading edge of the nictitans is depigmented and the palpebral surface is red and thickened. Treatment is similar to that for typical CSK.
Affected dogs should not be used for breeding. Breeding of close relatives should be avoided as well.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.
Roberts, S.M. 1995. Pannus. In J.D. Bonagura and R.W. Kirk (eds.). Kirk's Current Veterinary Therapy XII Small Animal Practice. p. 1245-1248. W.B. Saunders Co., Toronto. - This has good information on treatment, including for advanced or refractory lesions.