Refinement and revalidation of the Equine Ophthalmic Pain Scale: R-EOPS a new scale for ocular pain assessment in horses.

This study addresses the refinement and revalidation of a composite pain scale that focuses on equine facial expressions and behavioural indicators as exhibitions of ophthalmic pain. This scale included only Behavioural and Facial and Ocular expression indicators and, compared to the first version of Equine Ophthalmic Pain Scale (EOPS), item descriptors and related ratings were changed. Thirteen horses with ocular diseases that required medical or surgical treatment were enroled (group P). In each animal, the refined EOPS (R-EOPS) was applied prior to any treatment (T0) and one week later (T7). The R-EOPS was applied twice, 7 days apart, to 16 healthy control horses (group C). Two 30-second videos were recorded each time to allow the retrospective analysis by eight observers. Inter-observer reliability of items was moderate or substantial (Krippendorff's alpha, Kα>0.40) while their intra-observer reliability was substantial or almost perfect for most items (Kα ≥0.61). Both inter- and intra-observer reliability of Total Score (TS) were however excellent (Intraclass Correlation Coefficients, ICC>0.75). The TS also showed good reproducibility (Kendall coefficient=0.786, ICC=0.684) and high consistency of its items (Cronbach's α=0.847). The comparison between groups as well as the sensitivity and specificity values supported the validity of the R-EOPS. In particular, for each extra point added to the TS, the risk of the horse having pain increased by more than two times (Odds Ratio=2.079, 95%CI=1.542-2.804; P<0.001). The Receiver Operating Characteristic analysis identified 6 as the threshold value of R-EOPS for discriminating horses with ocular pathology (sensitivity=83%, specificity=100%). This scale may be an effective tool for reliably assessing the pain level in horses with ophthalmic diseases and potentially guiding pain management although it still requires large-scale application and external validation.

Development and preliminary validation of a pain scale for ophthalmic pain in horses: The Equine Ophthalmic Pain Scale (EOPS).

The purpose of this study was to describe the development and preliminary validation of a composite pain scale, called the Equine Ophthalmic Pain Scale (EOPS), to assess ocular pain in horses. Indicators associated with ocular pain were selected and classified as behavioural, physiological or ocular expressions. Eight horses diagnosed with ocular or adnexa diseases that required medical or surgical treatment were enrolled in the study (group P). The developed EOPS was applied at the baseline (T0) and 1 week later (T7). Moreover, the EOPS was applied twice, 1 week apart, to 15 healthy control horses (group C). Videos of 60-80 s duration of all assessments were retrospectively analysed by seven masked observers, who scored items included in the behavioural and ocular expression categories of the EOPS. The inter- and intra-observer reliability was excellent (intraclass correlation coefficients ≥0.75) for most of the scored items. Cronbach's alpha (0.76) indicated that the EOPS had good internal consistency. The total score (TS), calculated as the sum of all scores, differed between groups C and P at T0 (P < 0.001) and reduced after medical/surgical treatment in group P (P = 0.017), indicating the responsiveness of the EOPS. Moreover, the area under the curve (AUC=0.918, 95% confidence interval = 0.815-1.000; P < 0.001) indicated that the EOPS was very accurate for distinguishing healthy from pathological animals. Sensitivity and specificity of EOPS to identify horses with ocular pathology (at the optimal cut-off, i.e. TS ≥ 7) were 81.3% and 100.0%, respectively. However, 'overall behaviour', 'position inside the box', 'ear movements' and 'head position' items as well as physiological parameters, showed sub-optimal reliability, consistency and/or item-total correlation, suggesting that there is still room to improve this composite scale.