Scleritis

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Scleritis and episcleritis in a dog due to ulcerative keratitis[1]

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[2].

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[3] - Collie breeds[4]
- Chronic superficial keratitis - German Shepherds

In dogs, episcleritis may manifest as reddening of the sclera, or may worsen to necrotizing scleritis[9].

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[10].

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.

References

  1. Veterinary Vision
  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. Day MJ et al (2008) An immunohistochemical investigation of canine idiopathic granulomatous scleritis. Vet Ophthalmol 11(1):11-17
  4. Breaux CB et al (2007) Immunohistochemical investigation of canine episcleritis. Vet Ophthalmol 10(3):168-172
  5. Swinger RL et al (2009) Keratoconjunctivitis associated with Toxoplasma gondii in a dog. Vet Ophthalmol 12(1):56-60
  6. Barnes LD et al (2010) Surgical management of orbital nodular granulomatous episcleritis in a dog. Vet Ophthalmol 13(4):251-258
  7. Paterson S et al (1995) Systemic histiocytosis in the Bernese mountain dog. J Small Anim Pract 36(5):233-236
  8. Komnenou AA et al (2007) Ocular manifestations of natural canine monocytic ehrlichiosis (Ehrlichia canis): a retrospective study of 90 cases. Vet Ophthalmol 10(3):137-142
  9. Denk N et al (2012) A retrospective study of the clinical, histological, and immunohistochemical manifestations of 5 dogs originally diagnosed histologically as necrotizing scleritis. Vet Ophthalmol 15(2):102-109
  10. Grahn BH et al (1999) Diagnostic ophthalmology. Necrotic scleritis and uveitis. Can Vet J 40(9):679-680