Scleritis is an ophthalmic disease of the canine eye characterized by inflammation of the sclera (the white lining of the eyeball).
This condition may be a primary of secondary disease, and most primary cases are idiopathic and lack any evidence of underlying infectious causes.
Secondary episcleritis and episclerokeratitis, involving the epithelial lining of the sclera and cornea, may also be involved.
Scleritis usually occurs regionally with a proliferative response of inflammatory cells and granulation tissue which may extent into the cornea, resulting in ulcerative keratitis.
Scleritis may develop as a result of:
- - immune-mediated localized nodular granulomatous episclerokeratitis with systemic vasculitis in some cases - Collie breeds
- - Chronic superficial keratitis - German Shepherds
- Ulcerative keratitis
- Keratoconjunctivitis sicca
- Trauma, retrobulbar abscess, retrobulbar neoplasia, penetrating foreign bodies
- Ehrlichia spp
In dogs, episcleritis may manifest as reddening of the sclera, or may worsen to necrotizing scleritis.
Affected dogs usually present with sclera and conjunctival hyperemia, secondary conjunctivitis and blepharitis and well as photophobia and epiphora. Routine menace, auriculopalpebral and direct and consensual pupillary light reflexes are often normal.
A biopsy is usually required for definitive diagnosis, showing typical dense accumulation of plasma cells and lymphocytes. Severe forms of scleritis may progress with posterior segment involvement (secondary chorioretinal degeneration), scleral thinning and corneal dystrophy.
Treatment involves anti-inflammatory medications (corticosteroids, cyclosporine, azathioprine) given topically, subconjunctivally and occasionally systemically. Most cases respond well to a single subconjunctival injection of 4-8 mg triamcinolone with continued topical 1% prednisolone suspension once or twice daily.
The topical medication is reduced in frequency slowly over 2-3 months although many cases require life-time (once daily to every other day) therapy.
Severe cases may fulminate into nodular granulomatous or necrotizing scleritis with secondary exophthalmos, requiring enucleation.
- Veterinary Vision
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