Design and Development of a Snellen Chart Projector for Myopia Patients with a Patient Response Feature

Abstract

Visual acuity (visus) examination is a fundamental procedure for detecting refractive errors, particularly myopia. In practice, visual acuity assessment is still commonly performed using conventional Snellen Chart cards, which have limitations in terms of practicality, display consistency, and result recording. This study aims to design and develop a microcontroller-based Snellen Chart Projector with a patient response feature as an assistive device for visual acuity examination. The developed system consists of integrated software, hardware, and mechanical design, and is capable of displaying Snellen optotypes in accordance with standard letter sizes and a six-meter examination distance. The research methods include system design, functional testing of each component, accuracy testing of the TF-Luna distance sensor, verification of optotype size, and device trials involving respondents accompanied by feasibility assessment using questionnaires. The test results indicate that the system operates as designed, with distance sensor accuracy exceeding 99% and stable, consistent optotype display. Respondent trials demonstrate positive evaluations of the device’s feasibility. Therefore, the developed Snellen Chart Projector is considered accurate and feasible for use as an alternative visual acuity examination tool for patients with myopia.