The contact lens impact on quality of life (CLIQ) questionnaire: development and validation. Invest Ophthalmol Vis Sci.

PURPOSE. To develop and validate a questionnaire for the measurement of the impact of contact lenses on quality of life (QoL): The Contact Lens Impact on Quality of Life (CLIQ) Questionnaire. METHODS. The questionnaire was developed and validated using conventional methods and Rasch analysis to assure content validity, repeatability, construct validity, and low respondent burden. Item identification and selection (647 items) were performed with an extensive literature review, professional advice, and lay focus groups. Item reduction used focus groups and data obtained from 161 subjects completing a 90-item pilot questionnaire. Validity and reliability, from data of 128 additional subjects, were assessed using Rasch analysis, intraclass correlation coefficient, and Bland-Altman limits of agreement. RESULTS. A 28-item CLIQ Questionnaire was developed and shown to have good validity and reliability by Rasch analysis statistics: real person separation, 2.02; model person separation, 2.17; reliability, 0.80; root mean square measurement error, 2.73; mean square Ϯ SD infit, 1.01 Ϯ 0.18; outfit, 1.01 Ϯ 0.19. The items (mean score, 49.8 Ϯ 4.9) were well targeted to the subjects (mean score, 51.2 Ϯ 6.2) with a mean difference of 1.35 (scale range, 0 -100) units