Validation of the Greek version of the contact lens dry eye questionnaire-8 (CLDEQ-8)

Purpose: Contact lens discomfort (CLD) has been cited as one of the prime reasons for discontinuing contact lens wear. The CLDEQ-8 was created in 2008 to reflect status of and change in overall opinion of soft contact lenses. The purpose of this study is to examine the validity and reliability of a Greek version of the Contact Lens Dry Eye Questionnaire-8 (CLDEQ-8), using Rasch statistical analysis.Methods: This an observational prospective study of 150 consecutive patients who received soft contact lenses and were followed through with a single follow-up appointment up to a year following their initial one. The patients filled in the Greek versions of the CLDEQ-8, the Ocular Surface Disease Index (OSDI) and a self-report item on their experience of contact lens use. The CLDEQ-8 was analyzed with Rasch analytic methodology.Results: The original scoring system of the CLDEQ-8 had to be altered regarding the response categories collapsing in fewer options in items b, 2b, 3b and item 5 of the original scale. The revised scoring system proved more psychometrically valid and the CLDEQ-8 had good measurement precision, category threshold order, targeting and differential item functioning for gender. Two alternative result indexes are proposed, a symptom intensity index and a symptom frequency index to address dimensionality issues that are evident with the items relating to symptom intensity versus the rest. Results from the CLDEQ-8 correlated with the OSDI total score and the self-reported experience of contact lens use. Conclusions: The Greek version of the CLDEQ-8 is a psychometrically valid and reliable assessment tool for contact lens discomfort in Greek-speaking populations.