Chronic superficial keratitis

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Characteristic appearance of a dog's eye with chronic superficial keratitis with pannus formation[1]

Chronic superficial keratitis (pannus, Uberreiter’s disease) is an ophthalmic disorder of dogs characterized by solar keratitis and secondary immune-mediated degeneration of the canine cornea.

Although chronic superficial keratitis is found in many breeds it is most prevalent in female German Shepherds[2][3]. Other breeds which may be predisposed include the Belgian Tervuren, Greyhound, Siberian Husky, Australian Shepherd and Border Collie.

Although the etiology of this disease is multifactorial and not clearly understood, ultraviolet light is thought to initiate an immune-mediated stromal inflammatory response at the cornea surface through activation of major histocompatibility complex (MHC) class II antigens[4], suggesting a commonality between this canine disease and the human eye diseases pterygium and pinguecula[5]. Unlike the human condition where high levels of ultraviolet light in equatorial countries, dust and low humidity all play role in etiopathogenesis, chronic superficial keratitis in dogs is more common in dogs at higher altitude, but not with geographical location or humidity levels[6].

In dogs, this condition results in unilateral or bilateral superficial corneal opacification, fibrous tissue formation, vascularization, scarring and pigment formation which begins at the limbus and may extend over a large portion of the cornea[7].

Dogs with chronic superficial keratitis usually present with a visibly inflamed cornea that is highly vascularized and superficially proliferative. The condition is often painless but may result in epiphora, photophobia, conjunctivitis, blepharitis and in some cases, blindness in the affected eye.

A diagnosis is usually established by ophthalmic examination of the eye and in some cases, biopsy of corneal scrapings and ocular swabs for bacterial culture and viral PCR testing to exclude infectious causes. Histological examination of these samples invariably show infiltration of leucocytes into the anterior corneal stroma.

Immunohistochemical testing of tissue samples has revealed a preponderance of CD4 antigen expressing leucocytes[8].

Conservative treatment may include administration of ophthalmic drops containing cyclosporine[9] or tacrolimus, administered to the ocular surface three times a day. This may reduce the inflammatory process and neovascularisation, but in many cases does not inhibit the progress of the pigmentation[10].

A differential diagnosis would include adenoviral episcleritis[11], herpes viral keratitis[12], squamous cell carcinoma[13] and corneal hemangiosarcoma[14].

Topical ophthalmic solutions containing dexamethasone, tacrolimus, pimecrolimus or cyclosporine are usually indicated and may be sufficient to manage the condition[15]. Cyclosporin appears to promote better tear production than glucocorticoids[16].

Treatment with ocular drops containing 0.02% tacrolimus and 50% DMSO, administered to the ocular surface three times a day, have shown to be efficacious[17]

In severe refractory cases, surgical debridement via keratectomy or use of radiation therapy[18] may ameliorate the condition.

No positive effects have been reported through use of contact lenses for this condition[19] and use of canine sunglasses may be prudent if owner compliance is positive.

References

  1. David Williams.org
  2. Rapp E & Kölbl S (1995) Ultrastructural study of unidentified inclusions in the cornea and iridocorneal angle of dogs with pannus. Am J Vet Res 56(6):779-785
  3. Jokinen P et al (2011) MHC class II risk haplotype associated with canine chronic superficial keratitis in German Shepherd dogs. Vet Immunol Immunopathol 140(1-2):37-41
  4. Williams DL (2005) Major histocompatibility class II expression in the normal canine cornea and in canine chronic superficial keratitis. Vet Ophthalmol 8(6):395-400
  5. Rezvan F et al (2012) The prevalence and determinants of pterygium and pinguecula in an urban population in Shahroud, Iran. Acta Med Iran 50(10):689-96
  6. Chavkin MJ et al (1994) Risk factors for development of chronic superficial keratitis in dogs. J Am Vet Med Assoc 204(10):1630-1634
  7. Ledbetter EC et al (2012) Metaherpetic corneal disease in a dog associated with partial limbal stem cell deficiency and neurotrophic keratitis. Vet Ophthalmol Sep 7
  8. Williams DL (1999) Histological and immunohistochemical evaluation of canine chronic superficial keratitis. Res Vet Sci 67(2):191-195
  9. Williams DL (2010) Lack of effects on lymphocyte function from chronic topical ocular cyclosporine medication: a prospective study. Vet Ophthalmol 13(5):315-320
  10. Balicki I (2012) Clinical study on the application of tacrolimus and DMSO in the treatment of chronic superficial keratitis in dogs. Pol J Vet Sci 15(4):667-676
  11. Andrew SE (2008) Immune-mediated canine and feline keratitis. Vet Clin North Am Small Anim Pract 38(2):269-290
  12. Ledbetter EC et al (2006) Corneal ulceration associated with naturally occurring canine herpesvirus-1 infection in two adult dogs. J Am Vet Med Assoc 229(3):376-384
  13. Dreyfus J et al (2011) Superficial corneal squamous cell carcinoma occurring in dogs with chronic keratitis. Vet Ophthalmol 14(3):161-168
  14. Haeussler DJ et al (2011) Primary central corneal hemangiosarcoma in a dog. Vet Ophthalmol 14(2):133-136
  15. Nell B et al (2005) The effect of topical pimecrolimus on keratoconjunctivitis sicca and chronic superficial keratitis in dogs: results from an exploratory study. Vet Ophthalmol 8(1):39-46
  16. Williams DL et al (1995) Comparison of topical cyclosporin and dexamethasone for the treatment of chronic superficial keratitis in dogs. Vet Rec 137(25):635-639
  17. Balicki I (2012) Clinical study on the application of tacrolimus and DMSO in the treatment of chronic superficial keratitis in dogs. Pol J Vet Sci 15(4):667-676
  18. Allgoewer I & Hoecht S (2010) Radiotherapy for canine chronic superficial keratitis using soft X-rays (15 kV). Vet Ophthalmol 13(1):20-25
  19. Denk N et al (2011) The effect of UV-blocking contact lenses as a therapy for canine chronic superficial keratitis. Vet Ophthalmol 14(3):186-194