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

Abstract

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. 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. 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. 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. 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. 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. 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.