Validity and Reliability of a Novel Ocular Pain Assessment Survey (OPAS) in Quantifying and Monitoring Corneal and Ocular Surface Pain

Date Published:

2016 Jul

Abstract:

PURPOSE: To validate the Ocular Pain Assessment Survey (OPAS), specifically designed to measure ocular pain and quality of life for use by eye care practitioners and researchers. DESIGN: A single-center cohort study was conducted among patients with and without corneal and ocular surface pain at initial and follow-up visits over a 6-month period. The content of the OPAS was guided by literature review, a body of experts, and incorporating conceptual frameworks from existing pain questionnaires. The Wong-Baker FACES Pain Rating Scale served as the gold standard for measuring the intensity of ocular pain. PARTICIPANTS: A total of 102 patients aged 18 to 80 years completed the OPAS at the initial visit. A total of 21 patients were followed up after treatment. METHODS: Indices of validity and internal consistency (Spearman's rank-order, rs, or Pearson's correlation coefficients, rp), and coefficient of reliability (Cronbach's α) were determined in addition to equivalence testing, exploratory factor analysis (EFA), and diagnostic analysis. MAIN OUTCOME MEASURES: Eye pain intensity was the primary outcome measure, and interference with quality of life (QoL), aggravating factors, associated factors, associated non-eye pain intensity, and self-reported symptomatic relief were the secondary outcome measures. RESULTS: The OPAS had criterion validity at both initial (rs = 0.71; n = 102; P < 0.01) and follow-up visits (rs = 0.97; n = 21; P < 0.01). Equivalence tests yielded OPAS and gold standard equivalence for both the initial and follow-up visits. The EFA supported 6 subscales (eye pain intensity at 24 hours and 2 weeks, non-eye pain intensity, QoL, aggravating factors, and associated factors) confirming multidimensionality. Cronbach's α >0.83 for all subscales established strong internal consistency, which correlated with the gold standard, including 24-hour eye pain intensity and QoL interference scores (rp = 0.81, 0.64, respectively P < 0.001). At follow-up, reduction in pain scores was accompanied by improvement in all dimensions of the OPAS. Percentage change in QoL correlated to percentage change in the gold standard (rp = 0.53; P < 0.05). The OPAS was sensitive (94%), specific (81%), and accurate (91%), with a diagnostic odds ratio >50. CONCLUSIONS: The OPAS is a valid, reliable, and responsive tool with strong psychometric and diagnostic properties in the multidimensional quantification of corneal and ocular surface pain intensity, and QoL.