Canis ISSN: 2398-2942

Chronic superficial keratitis

Synonym(s): Pannus, Überreiter's syndrome

Contributor(s): Dennis E Brooks, David L Williams, Natasha Mitchell

Introduction

  • Cause: immune-mediated corneal and conjunctival condition affecting primarily the middle-aged German Shepherd dog German Shepherd Dog, but several other breeds can be affected. Ultra-violet light is a predisposing factor.
  • Signs: bilateral lesions first seen at ventro-lateral limbus.
  • Progressive, potentially blinding, but no discomfort or irritation.
  • Same as keratitis Keratitis.
  • Diagnosis: history, clinical signs, ophthalmic examination.
  • Treatment: chemotherapy. Topical steroid, cyclosporine or a combination.
  • Prognosis: will recur without regular treatment.

Pathogenesis

Etiology

  • Immune-mediated.
  • Breed predisposition for German Shepherds shows heritable nature but more likely as a polygenic inheritance than a single gene defect.

Specific

  • Ultraviolet/solar radiation involved in pathogenesis.
  • Altitude-more difficult to control at high altitudes. Latitude and longitude are less important, only being relevant with regard to sunlight exposure.

Pathophysiology

  • Inflammation of the cornea that does not retain fluorescein (non-ulcerative). Alteration of corneal clarity may be due to neovascularization, edema, cellular infiltration, pigmentation, lipid or calcium deposition and scarring (fibrosis).
  • Immune-mediated (cell-mediated immunity to corneal/conjunctival antigens) - ultraviolet radiation may alter immunogenicity of antigens), vascular lesion appears at temporal limbus and invades cornea - pigmentation follows vascularization. May also affect nictitating membrane. Epithelium remains intact.
  •  Pigmentary keratitis Pigmentary keratitis - usually associated with chronic keratitis, pigment produced in epithelium, anterior stroma and migrates from perilimbal melanocytes, secondary to corneal vascularization. Impairs vision when becomes central. Note differential diagnoses.
  • Stages:
    • Lymphocyte and plasma cell infiltration.
    • Vascularization.
    • Pigmentation.
    • Fibrovascular plaque formation.
  • A composite of these stages is seen: varying pigmentation, vascularization and fibrovascular plaque formation depending on severity and chronicity. May be concurrent, chronic conjunctivitis and plasma cell thickening of the membrana nictitans.

Timecourse

  • Life-long disease.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Azoulay T (2014) Adjunctive cryotherapy for pigmentary keratitis in dogs: a study of 16 corneas. Vet Ophthalmol 17, 241-249 PubMed.
  • Williams D L, Hoey A J & Smithermann P (1995) Comparison of topical cyclosporin and dexamethasone for the treatment of chronic superficial keratitis in dogs. Vet Rec 137 (25), 635-639 PubMed.
  • Chavkin M J, Roberts S M et al (1994) Risk factors for development of chronic superficial keratitis in dogs. JAVMA 204 (10), 1630-1634 PubMed.
  • Petrick S W & van Rensburg I B K (1989) Corneal anatomical differences in the etiology of chronic superficial keratitis. JSAP 30 (8), 449-453 PubMed.

Other sources of information

  • Gelatt K N (ed) (1999) Veterinary Ophthalmology. 3rd Edn. Lippincott: Williams & Wilkins. ISBN 0683300768.


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