Background: Diabetic retinopathy (DR) is a significant complication of diabetes, potentially leading to vision loss. Effective self-care and management are crucial to prevent its progression. Mobile Health (mHealth) applications offer a promising solution for supporting DR patients in self-care by providing continuous monitoring, education, and reminders. Objectives: This Participatory Design study aimed to create and assess a mobile health app to help diabetic retinopathy patients manage their condition through self-care. Methods: This practical research was carried out in 2024 over two stages: Design and Evaluation. First, we determined the functional requirements and developed a conceptual model of the application using Microsoft Visio 2021. In the next stage, we evaluated the application using the Mobile Application Usability Questionnaire (MAUQ) and gathered feedback from patients with diabetic retinopathy to understand their views on the application's usability. Results: The application's main features included reminders, alerts, educational content, and useful links. Thirty users with diabetic retinopathy participated in the usability testing. The participants expressed a high level of satisfaction with the application (mean score: 5.67 ± 1.04 out of a maximum of 7.00). Conclusions: The mHealth application for diabetic retinopathy self-care demonstrated high usability and potential to support patients in managing their condition. Future work should focus on integrating more advanced features and conducting long-term studies to assess the app's impact on clinical outcomes.