Psychometric properties of the National Eye Institute–Refractive Error Quality of Life instrument

Abstract

Objective To estimate the psychometric properties of a vision-targeted measure of health-related quality of life, the National Eye Institute–Refractive Error Quality of Life survey (NEI-RQL), which includes 13 scales designed to assess the impact of refractive error and its correction on day-to-day life. Design Cross-sectional survey. Participants The NEI-RQL was self-administered by 667 myopes, 380 hyperopes, and 114 emmetropes recruited from the practices of 6 medical centers. All participants had near and distance visual acuity of 20/32 or better in the worse eye while benefiting from their current method for correction of refractive error (glasses, contact lens, refractive surgery). Methods Mean scores, standard deviations, internal consistency reliability, and test–retest intraclass correlations were estimated for the NEI-RQL scales. Item discrimination was assessed by item–scale correlations. Construct validity was evaluated by assessing the sensitivity of scale scores to type of refractive error, type of refractive error correction, and spherical equivalent. Construct validity of the NEI-RQL was compared to those of the Medical Outcomes Study 36-item short-form health survey (SF-36) and the National Eye Institute Vision Functioning Questionnaire (NEI VFQ-25) in a random subsample of respondents. Main outcome measures The 13 NEI-RQL scales—clarity of vision, expectations, near vision, far vision, diurnal fluctuations, activity limitations, glare, symptoms, dependence on correction, worry, suboptimal correction, appearance, and satisfaction with correction. Results Emmetropes tended to score significantly better on the NEI-RQL scales than myopes and hyperopes. The method of refractive error correction was also associated with NEI-RQL scores. In addition, the NEI-RQL multi-item scales accounted for 29% of the variance in the NEI-RQL satisfaction with correction item beyond that explained by the SF-36 and the NEI VFQ-25. Conclusion These results support the reliability and construct validity of the NEI-RQL. The instrument appears to be useful for comparisons of people with different types of correction for refractive error.