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Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • EK is a relatively common disease of horses with an unknown etiology
  • An accumulation of mainly eosinophils and a few mast cells in the affected cornea is characteristic
  • Systems affected—ophthalmic

Signalment!!navigator!!

All ages and breeds affected.

Signs!!navigator!!

  • The clinical appearance of EK in horses can be highly variable
  • Mild to severe blepharospasm, epiphora, chemosis, conjunctival hyperemia, mucoid discharge, corneal ulcers, and associated raised, white, necrotic plaques
  • A subset of horses with minimal discomfort and more chronic, nonulcerated, proliferative lesions of the cornea has been observed

Causes and Risk Factors!!navigator!!

  • The true etiology of this condition is yet to be determined
  • Possibly allergic or parasitic
  • May be immune mediated

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

Allergic or hypersensitivity keratitis/keratoconjunctivitis; eosinophilic granuloma; bacterial, mycotic, or viral keratitis; foreign body reaction; onchocerciasis; habronemiasis; corneal neoplasia such as squamous cell carcinoma or mastocytoma; traumatic keratitis with scarring; calcium or lipid degeneration.

CBC/Biochemistry/Urinalysis!!navigator!!

N/A

Other Laboratory Tests!!navigator!!

  • Rule out infectious causes (bacterial or fungal) with corneal scrapings for cytology and culture
  • Corneal scrapings of EK typically contain degenerate collagen, numerous eosinophils, and a few neutrophils, macrophages, lymphocytes, and mast cells
  • Cytology is usually diagnostic; however, biopsy for histology will help to confirm the diagnosis if corneal scrapings are not conclusive
  • In cases with an associated conjunctivitis, the distribution of inflammatory cells in a sample from the conjunctiva resembles that from the cornea

Imaging!!navigator!!

N/A

Other Diagnostic Procedures!!navigator!!

N/A

Pathologic Findings!!navigator!!

Histologic examination finds eosinophilic, acellular granular material and subepithelial, fragmented degenerate collagen infiltrated by eosinophils, lymphocytes, plasma cells, and macrophages.

Treatment ⬆ ⬇

TREATMENT

  • Medical therapy is aimed at decreasing the inflammatory response within the cornea
  • Often combination therapy is necessary
  • Superficial lamellar keratectomy to remove plaques may speed healing

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

  • Topical corticosteroids (1% prednisolone acetate or 0.1% dexamethasone) 3 or 4 times a day in early stages (despite corneal ulcerations)
  • Topical cyclosporine 0.2–2.0% BID or TID
  • Topical mast cell stabilizers such as 4% cromolyn sodium (cromoglicic acid) and 0.01% lodoxamide or olopatadine can be helpful in some cases 3–4 times a day
  • Topical antibiotics (e.g. bacitracin–neomycin–polymyxin B, chloramphenicol), 1% atropine, and 0.03% phospholine iodide (ecothiopate iodide) BID in combination with systemic NSAIDs (e.g. flunixin meglumine 0.25–1 mg/kg BID PO, IM, IV) to protect the corneal wounds from secondary infection and treat any associated uveitis
  • Once improvement is noted, medical therapy should be tapered slowly

Contraindications/Possible Interactions!!navigator!!

  • Phospholine iodide is an acetylcholinesterase inhibitor which may be larvicidal for parasites. Its use is controversial
  • The use of topical NSAIDs may increase the severity of clinical signs in the horse since they do not inhibit and may potentiate leukotrienes
  • Horses receiving topically administered atropine should be monitored for signs of colic

Follow-up ⬆ ⬇

FOLLOW-UP

Expected Course and Prognosis

  • Although therapy is often prolonged and these lesions are often slow to heal, the prognosis for resolution with diligent treatment is good
  • Scarring of the cornea may occur
  • May recur. May be seasonal

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

Uveitis

Abbreviations!!navigator!!

  • EK = eosinophilic keratitis/keratoconjunctivitis
  • NSAID = nonsteroidal anti-inflammatory drug

Suggested Reading ⬆ ⬇

Brooks DE. Ophthalmology for the Equine Practitioner, 2e. Jackson, WY: Teton NewMedia, 2008.

Brooks DE, Matthews AG. Equine ophthalmology. In: Gelatt KN, ed. Veterinary Ophthalmology, 4e. Ames, IA: Blackwell, 2007:1165–1274.

Gilger BC, ed. Equine Ophthalmology, 3e. Ames, IA: Wiley Blackwell, 2017.

Author(s) ⬆

Authors: Caryn E. Plummer

Consulting Editor: Caryn E. Plummer