Clinical features and outcomes of horses presenting with presumed equine immune mediated keratitis to two veterinary hospitals in the United Kingdom and Finland: 94 cases (2009-2021).

BACKGROUND

There is limited literature regarding equine immune mediated keratitis (IMMK) in Europe. North America-based publications describe minimal blepharospasm, rare corneal ulceration and no uveitis; clinical impression suggests these are seen in Europe.

OBJECTIVES

Assess the prevalence of blepharospasm, corneal ulceration and uveitis and their impact on outcome in horses diagnosed with IMMK in Europe (UK and Finland).

STUDY

DESIGN

Retrospective case series.

METHODS

Clinical records of 94 horses with IMMK were evaluated. The UK and Finland populations were comparable; therefore, descriptive statistics were performed on combined data on subtypes of IMMK and clinical features. Odds ratios (OR) and confidence intervals (CI) were calculated for impact of blepharospasm, ulceration or presence of uveitis on the outcome of enucleation and treatment duration.

RESULTS

IMMK subtype was classified as 10/94 (10.6%) epithelial, 50/94 (53.2%) anterior stromal, 14/94 (14.9%) mid-stromal, 4/94 (4.25%) endothelial and 16/94 (17.0%) unrecorded. After excluding three horses with incidental corneal ulceration, blepharospasm was documented in 34/91 (37.4%), corneal ulceration in 26/91 (28.6%), and signs of uveitis in 23/91 (25.3%) horses. Increased odds of enucleation were significantly associated with the presence of blepharospasm (OR 5.5, 95% CI 1.6-19.4, p = 0.008) and signs of uveitis (OR 8.9, 95% CI 2.6-30.8, p < 0.001), but not corneal ulceration. The presence of blepharospasm, corneal ulceration or uveitis did not significantly alter the odds of ongoing medication.

MAIN LIMITATIONS: Data were collected over a wide timeframe; the diagnosis was mainly made without histopathology; a broad definition of uveitis was used and there was a bias towards complicated cases being retained for follow-up.

CONCLUSIONS

The clinical features of IMMK were similar between two European countries but differed to USA descriptions. Blepharospasm, corneal ulceration and signs of uveitis can occur with IMMK; presence of blepharospasm and uveitis increase the odds of enucleation.