Development and validation of a multidimensional quality-of-life scale for myopia.
BACKGROUND: Five dimensions of health-related quality of life in myopia were hypothesized to affect satisfaction with visual correction modality. Items on these dimensions reflected the frequency of visual compromise and ocular symptoms; individual tolerance of these compromises and symptoms; cosmesis; psychological constructs (including situation-dependent characteristics such as adaptability, self-efficacy, and subjective well-being); and personality traits such as extraversion and introversion. METHODS: Psychologically oriented items and visually oriented items were developed in two stages involving 1,647 participants. Item development was based on a comprehensive literature review, interviews with experts, myopic subjects, and graduate students, and written feedback. Items were selected through factor analysis and the examination of their ability to discriminate between treatment conditions (spectacle wear, daily use of contact lenses, continuous use of contact lenses, or laser-assisted in-situ keratomileusis for myopia). After development, selection, and validation of the psychological items and then the vision items, a final multidimensional scale combining both types of items was designed. The scale was administered to 124 subjects whose myopia was corrected by one of several treatment modalities to determine final construct validity. RESULTS: Using principal axis factoring and oblimin with Kaiser normalization rotation methods, five factors with strong item loadings evolved as hypothesized. The final multidimensional scale consisted of 13 items related to specific aspects of frequency of visual compromise and ocular symptoms with 13 corresponding items for level of tolerance for these problems; three items related to cosmesis; 10 items related to psychological characteristics; and six items related to personality traits. Good internal consistency in each factor (Cronbach's alpha range, 0.76 to 0.92) for the scale was evident. DISCUSSION: This report describes the development and validation of an easily administered, short, effective multidimensional health-related quality-of-life questionnaire for use in selecting and measuring success of methods for correcting myopia.