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Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • Keratopathy or keratitis with associated conjunctivitis and epiphora putatively caused by EHV-2
  • Systems affected—ophthalmic

Signalment!!navigator!!

All ages and breeds affected; may be seen in herds.

Signs!!navigator!!

  • Multiple, superficial epithelial to subepithelial anterior stromal, whitish, punctate (organized in a grid-like manner), or linear opacities of the cornea, which may become confluent with chronicity, leading to the formation of a geographic corneal opacification (leukoma), with or without fluorescein and/or rose bengal dye retention
  • Varying amount of ocular pain, conjunctivitis, corneal edema, epiphora, corneal vascularization, and iridocyclitis
  • Drooping of upper lid eyelashes may occur, and is associated with discomfort

Causes and Risk Factors!!navigator!!

EHV-2 and, to a lesser degree, EHV-5 are the suspected agents, but equal prevalence of positive PCR assays for EHV-2 and EHV-5 have been found in normal control horses.

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • IMMK
  • Superficial keratomycosis
  • Superficial corneal ulcers
  • Equine recurrent uveitis
  • Conjunctivitis
  • Glaucoma
  • Blepharitis
  • Dacryocystitis

CBC/Biochemistry/Urinalysis!!navigator!!

N/A

Other Laboratory Tests!!navigator!!

  • Rule out other infectious causes (bacterial or fungal) of keratitis with corneal scrapings for cytology and culture
  • Culturing virus from ocular specimens, and identification of viral isolates by use of PCR or electron microscopy

Imaging, Other Diagnostic Procedures, Pathologic Findings!!navigator!!

Conjunctival and/or corneal biopsy and identification of viral isolates by use of PCR or electron microscopy.

Treatment ⬆ ⬇

TREATMENT

  • Outpatient treatment may not lead to acceptable control of the associated signs of disease because owner compliance and cooperation from the horse is necessary for extended duration
  • Treatment may lead to amelioration of signs; however, recurrences or a waxing and waning pattern of progression is often observed in affected horses
  • Affected horses may present with aggressive behavioral issues that may reveal ocular discomfort. Such behavior will generally disappear once the disease has been controlled
  • Activity should be reduced during periods of active inflammation, especially if accompanied by discomfort

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

  • Topical idoxuridine, trifluorothymidine, or acyclovir (aciclovir)—initially every 2 h, then 4–6 times per day
  • Topical NSAIDs (diclofenamic acid, flurbiprofen, or bromfenac every 12 h) may be beneficial in reducing the effects of active inflammation
  • Topical antiproteases, such as serum, may aid healing if a corneal ulcer is present

Contraindications/Possible Interactions!!navigator!!

  • Topical corticosteroids are contraindicated as they may result in exacerbation of an underlying bacterial or fungal infection (which may be extremely difficult to completely rule out) and may ultimately lead to pseudo-recurrence
  • Horses presenting with only punctate epithelial/subepithelial anterior stromal corneal opacification without ocular discomfort, conjunctival hyperemia, chemosis, or corneal vascularization may be self-limiting or without clinical significance. In these cases, initiation of aggressive medical therapy should be considered carefully, as this may lead to an exacerbation of clinical signs and the development of pseudo-recurrent inflammation

Follow-up ⬆ ⬇

FOLLOW-UP

Expected Course and Prognosis

Treatment is often successful in the short term, but recurrence is common.

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

Superficial keratomycosis, superficial forms of IMMK, secondary bacterial infection.

Age-Related Factors!!navigator!!

Multiple foals or adults in a herd may be affected.

Abbreviations!!navigator!!

  • EHV = equine herpesvirus
  • IMMK = immune-mediated keratitis
  • NSAID = nonsteroidal anti-inflammatory drug
  • PCR = polymerase chain reaction

Suggested Reading ⬆ ⬇

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

Hollingsworth SR, Pusterla N, Kass PH, et al. Detection of equine herpesvirus in horses with idiopathic keratoconjunctivitis and comparison of three sampling techniques. Vet Ophthalmol 2015;18(5):416–421.

Matthews AG, Brooks DE, Clode AB. Diseases of the equine cornea. In: Gilger BC, ed. Equine Ophthalmology, 3e. Ames, IA: Wiley Blackwell, 2017:252–368.

Author(s) ⬆

Author: Richard J. McMullen Jr.

Consulting Editor: Caryn E. Plummer

Acknowledgment: The author and editor acknowledge the prior contribution of Andras M. Komaromy and Dennis E. Brooks.