The Ocular Surface Disease Index (OSDI), developed by the Outcomes Research Group at Allergan Inc (Irvine, Calif),8 is a 12-item questionnaire designed to provide a rapid assessment of the symptoms of ocular irritation consistent with dry eye disease and their impact on vision-related functioning. The initial OSDI items were generated from patient comments from several years of clinical studies conducted by Allergan Inc, several quality-of-life instruments, and suggestions from clinical investigators. This item list was then distributed to more than 400 patients with dry eye disease, who were asked to indicate whether they experienced any of the symptoms or problems on the list and, if so, how often. This information was combined with responses from 44 patients with dry eye disease and 2 health professionals who were asked to list aspects of their dry eye condition that affected their daily activities. Item responses were then categorized, and categories mentioned more than once were formatted into an initial questionnaire. This initial questionnaire included 40 items, which were later reduced to the final 12 questions on the basis of validity and reliability data from 3 groups (2 small groups of patients with dry eye and one phase II clinical trial group).