Episcleritis

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The right eye of a 13-year-old Cocker Spaniel with episcleritis[1]

Episcleritis is an ophthalmic disease of the canine eye characterized by inflammation of the epithelial lining of the sclera.

Scleritis is usually involved as well in cases involving the whole eye[2].

Primary episcleritis may be diffuse or nodular and Cocker Spaniel and Golden Retriever breeds appear to be predisposed[3].

Diffuse episcleritis (simple episcleritis) may be unilateral or bilateral and presents as an elevated sector lesion, posterior to the limbus, with episcleral and conjunctival vascular congestion. The perilimbal cornea adjacent to the inflammation is usually edematous and may be vascularized[4].

The nodular form is most commonly diagnosed in Collie breeds and is commonly referred to as nodular granulomatous episclerokeratitis, although alternative nomenclature includes nodular fasciitis, fibrous histiocytoma, proliferative conjunctivitis, pseudotumor, and collie granuloma[5]. Nodular granulomatous episclerokeratitis is usually bilateral and manifests clinically as a raised pink mass affecting the temporal limbus, cornea, and the nictitating membrane. Diffuse and nodular episcleritis are similar histologically and consist of a cellular infiltrate dominated by lymphocytes, plasma cells, and macrophages[6]. The immunopathogenesis of this condition likely involving primary type IV hypersensitivity, with a probable underlying type III involvement[7].

The prognosis for resolution of NGE and bilateral episcleritis without long-term medical therapy is poor[8]. Medical therapy consisting of topical corticosteroids such as 1% prednisolone acetate or 0.1% dexamethasone four times daily for several weeks.

In some cases, systemic corticosteroids or other immunomodulators, such as azathioprine, may be necessary to bring about remission. Once remission is achieved, the frequency of administration can be gradually tapered. Although some cases may resolve completely without recurrence after withdrawal of therapy, most will require long-term maintenance therapy to maintain remission.

References

  1. Sandmeyer LS et al (2008) What are your clinical diagnosis, differential diagnoses, therapeutic plan, and prognosis? Diffuse episcleritis of the right eye. Can Vet J 49(1):89-90
  2. Grahn BH & Sandmeyer LS (2008) Canine episcleritis, nodular episclerokeratitis, scleritis, and necrotic scleritis. Vet Clin North Am Small Anim Pract 38(2):291-308
  3. Deykin AR et al (1997) A retrospective histopathologic study of primary episcleral and scleral inflammatory disease in dogs. Vet Comp Ophthalmol 7:245–248
  4. Whitley R & Gilger B (1999) Diseases of the canine cornea and sclera. In: Gelatt KN, editor. Veterinary Ophthalmology. 3. Philadelphia: Lippincott Williams & Wilkins. pp:635–673
  5. Paulson ME et al (1987) Nodular granulomatous episclerokeratitis in dogs: 19 cases. J Am Anim Hosp Assoc 190:1581–1587
  6. Fisher C (1983) Inflammatory diseases of the sclera and episclera. In: Peiffer RL Jr, editor. Comparative Ophthalmic Pathology. Springfield: Charles C Thomas. pp:272–288
  7. Day MJ et al (2008) An immunohistochemical investigation of canine idiopathic granulomatous scleritis. Vet Ophthalmol 11(1):11-17
  8. Breaux CB et al (2007) Immunohistochemical investigation of canine episcleritis. Vet Ophthalmol 10(3):168-172