HOW-TO SESSION: OPHTHALMOLOGY


berg et al13 reported EK in a group of three horses recurring in the summer months over a 2-year pe- riod. All three horses responded poorly to medical therapy with topical antibiotics and topical as well as systemic corticosteroids but demonstrated rapid resolution after a superficial keratectomy. Histo- pathology and transmission electron microscopy of the keratectomy specimens identified eosinophils in the anterior corneal stroma. Allergic dermatitis was diagnosed in two of these horses, raising the possibility of a multi-system eosinophilic disease process or general immunoglobulin E–mediated hy- persensitivity disease. Kafarnik15 reported a sin- gle case of EK in a 7-year-old Cob gelding with a 3-month history of bilateral corneal ulcers. Super- ficial keratectomy led to resolution in 14 days, with no recurrence reported in 6 months of follow-up. Diamond burr debridement has been used to treat horses previously diagnosed with EK and with sub- sequent nonhealing corneal ulcers.18 Taken to- gether, these cases support the hypothesis that superficial keratectomy may be associated with more rapid resolution of clinical signs than medical therapy alone. Although the superficial keratectomy has shown


A single case of EK in a 29-year-old donkey was reported by Jennings.11 The donkey presented with a 2-day history of unilateral ocular discharge and a limbal mass. After treatment with topical dexamethasone and topical antibiotics, the lesions had resolved at the time of a follow-up appointment 30 days after initiation of treatment. In another single case report of EK, bilateral conjunctival and periocular skin biopsies were performed in a 17- year-old Icelandic mare with a 4-week history of bilateral conjunctivitis.12 In this mare, BPV-1/-2 DNA and oncogene E5 transcript were identified, suggesting a role for a viral component in the devel- opment of EK in horses. The following year in a conference abstract, Sand-


cases of equine EK and provides additional evidence that EK is a recurrent, seasonal disease in horses. On the basis of this literature, medical manage-


ment of equine EK should include standard ulcer- ative keratitis regimen (described in Treatment Approach section) in addition to a short course of systemic corticosteroids to combat the plausible al- lergic hypersensitivity component. An H1-receptor antagonist, cetirizine, should also be prescribed as both an immediate treatment and future preventa- tive measure.17 Although use of topical corticoste- roids in some cases of EK may result in short-term improvement, the use of topical corticosteroids in the face of a corneal ulcer is dangerous because it may increase the incidence and severity of second- ary bacterial and fungal corneal infections.17


2. Clinical Signs and History


the most promise for achieving rapid resolution of EK, surgical intervention is not the best “first-line” treatment for mild or recurrent cases. In addition, even in cases with severe and prolonged disease, surgical intervention is often declined by owners because of concerns about risks of general anesthe- sia and/or financial constraints. Therefore, identi- fying the best non-surgical approach to treatment of EK is important and useful in managing a disease that has a seasonally reoccurring component. The most recent insight into medical management of EK is in a retrospective study of 46 eyes in 26 horses.17 In this study, the signalment, history of EK, pre- senting signs, medical therapy, time to resolution, and recurrence during a follow-up period (mean, 1.9; standard deviation [SD], 1.6; range, 0.3–4.7 years) were evaluated in horses diagnosed with EK from 2008 to 2012. The results of this retrospective study support the use of systemic corticosteroids and a systemic histamine 1(H1)-receptor antagonist in


Clinical signs of EK include moderate to severe oc- ular pain, caseous ocular discharge, severe conjunc- tival hyperemia and chemosis, and pink proliferative corneal plaques, most often originating at the corneolimbal junction.9–17 White, cellular plaques may be present overlying the pink prolifer- ative lesions. Individual cases of EK can present with clinical signs at any point along the clinical spectrum, from severe conjunctivitis and blepharitis with or without corneal ulceration, to geographic corneal ulceration with secondary bacterial and/or fungal involvement. The majority of horses are ex- quisitely painful on presentation with moderate to severe epiphora and blepharospasm. The disease can present unilaterally or bilaterally, and severity can differ between left eye and right eye when bilat- eral. Reflex uveitis is often present. There was a clear seasonal component, with 92% of cases in one study having developed clinical signs from June through October.17 Many horses present with a history of similar ophthalmic clinical signs observed by the owner dur- ing the summer and early fall months of previous years. In one study, 44% of horses diagnosed with EK had a 1- to 5-year history of confirmed EK.17 An owner may also report that within a single year, their horse exhibits repeated bouts of conjunctivitis, blepharitis, and corneal ulceration, which respond poorly to routine cornel ulcer management, includ- ing topical antibiotics and antifungals, systemic non-steroidal anti-inflammatory drug (NSAID) med- ication, and topical mydriatic/cycloplegic treatment. Although in many cases the definitive diagnosis of EKcannot be made for previous episodes, awareness of a possible recurrent disease process may raise a red flag to the clinician that this is not a typical case of ulcerative keratitis.


3. Examination and Diagnosis


A complete ophthalmic examination should be per- formed to rule out other causes of conjunctivitis, blepharitis, corneal ulceration, and anterior uveitis, if present. Differential diagnoses for EK include


AAEP PROCEEDINGS  Vol. 59  2013 161


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