Episcleritis is an ophthalmic disease of the canine eye characterized by inflammation of the epithelial lining of the sclera.
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.
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. 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. The immunopathogenesis of this condition likely involving primary type IV hypersensitivity, with a probable underlying type III involvement.
The prognosis for resolution of NGE and bilateral episcleritis without long-term medical therapy is poor. 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.
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