Objective: To assess the minimal clinically important difference (MCID) for the Ocular Surface Disease Index (OSDI; Allergan Inc, Irvine, California, holds the copyright), a 12-item patient-reported outcome questionnaire designed to quantify ocular disability due to dry eye disease.
Methods: Study data were collected within the Restasis Review of Efficacy and Safety vs Tears in the Relief of Dry Eye (RESTORE), an observational registry. A clinician global impression (CGI) and a subject global assessment (SGA) served as anchors to estimate the MCID for the overall OSDI score (range, 0-100). The overall OSDI score defined the ocular surface as normal (0-12 points) or as having mild (13-22 points), moderate (23-32 points), or severe (33-100 points) disease. RESTORE patients were included if they completed the OSDI at the baseline visit and at a follow-up visit and had a global change rating (SGA or CGI).
Results: Three hundred ten patients were included (82.3% white and 81.6% female [mean age, 57.8 years]). The CGI and SGA correlated with the OSDI score change for all OSDI categories except the normal category. The MCID ranged from 7.0 to 9.9 for all OSDI categories. The MCID ranged from 4.5 to 7.3 for mild or moderate disease and from 7.3 to 13.4 for severe disease.
Conclusions: Using observational data, we estimated the MCIDs for different baseline OSDI categories of dry eye disease. These results will assist clinicians and researchers when interpreting OSDI score changes.