INTRODUCTION: Mobile Applications (apps) are commonly used in the health care settings to improve the quality of care, however prior to the release of the app it is vital to evaluate its usability. Therefore, the aim of this study is to adapt the mobile Health App Usability Questionnaire (MAUQ) and measure the usability of the Eye donor Aust App using the modified instrument (m-MAUQ). METHODS: The study was undertaken using a convenience sample of 94 patients and their carers attending three eye clinics and one outpatient department in a large hospital in Sydney Australia. The study was conducted in two phases. Phase 1 involved the adaptation of the MAUQ, and validity testing of the modified version. Phase 2 included the usability evaluation of the Eye donor Aust App using the modified MAUQ (m-MAUQ). RESULTS: The m-MAUQ comprised of 15 items and the content validity of the instrument was considered satisfactory. Exploratory factor analysis supported a three-factor structure namely: ease of use and satisfaction (nine items), usefulness in obtaining information (three items), and system information arrangement (three items). The internal consistency for the subscales and the total scale was high with Cronbach's alpha values greater than 0.90. The usability score for the Eye donor Aust App was high (mean 5.99; SD 0.74). The construct validity was supported as there were no differences in usability scores among males and females. Older people found the app less useful for obtaining information about eye donation. CONCLUSIONS: The results support the use of the m-MAUQ as a valid instrument to measure the usability of the Eye Donor Aust App. This instrument requires further testing in other groups of people. Usability testing of the Eye Donor Aust app demonstrated that the participants were satisfied with the content and functionality of the app stating that it was well organised, visually appealing and user friendly. This result could translate into more people using the app and thereby increasing their knowledge and attitude towards eye donation as well as registering to become a donor.