In this service-learning engineering project, students follow the steps of the engineering design process to design a hearing testing device. More specifically, they design a prototype machine that can be used to test the peripheral vision of partially-blind, pre-verbal children. Students learn about the basics of vision and vision loss. They also learn how a peripheral vision tester for adults works (by testing the static peripheral vision in the four quadrants of the visual field with four controllable lights in specific locations). Then they modify the idea of the adult peripheral vision tester to make it usable for testing young children. The class designs and builds one complete prototype, working in sub-groups of four or five students each to build sub-components of the project design.