The reliability and validity of McMonnies Dry Eye Index.

OBJECTIVE The purpose of this report was to investigate the psychometric properties of the McMonnies questionnaire for dry eye disease. METHODS The instrument was administered to 75 patients with dry eye disease on two occasions. Additional dry eye clinical tests, patient-reported dry eye interviews, and the NEI-VFQ-25 were completed during these examinations. Reliability (internal consistency and test-retest), validity (concurrent and discriminant), and accuracy were assessed for McMonnies Index scores. RESULTS McMonnies Index showed poor internal consistency (Cronbach alpha = 0.43) and moderate test-retest reliability (ICC = 0.86, 95% confidence interval 0.76 to 0.90). The mean difference between visits was 0.49 (1-sample t test, t = 0.92, P = 0.36), and the 95% limits of agreement for test-retest reliability were -8.6 to +9.6. The instrument also showed fair concurrent validity, correlating only with the NEI-VFQ-25 pain subscale, but better discriminant validity when comparing mild and severe patients. Finally, the McMonnies Index demonstrated fair accuracy in identifying severe dry eye patients as defined by signs and symptoms (area under the ROC curve = 0.65). CONCLUSIONS The McMonnies Index demonstrates fair reliably and validity as a patient-reported instrument for use in patient care and clinical studies of patients with dry eye disease.