Although amblyopia is most successfully treated when detected in early childhood, many preschool-aged children are not being screened. This project explored the delivery of Web-based vision screenings, integrated with patient education, to parents and children, aged 3 to 6 years. Through a user-centered design methodology involving requirements gathering, iterative prototype development, and usability testing, a highly usable screening Website was created. Interviewing and testing parents and children in the home were essential in gathering accurate data about environments where the tool would actually be used. Frequent iterations of designing, testing, and modifying the tool were useful in identifying and correcting usability problems. Usability goals were set early in the project, and in the final phase a satisfaction questionnaire was administered to participants. Twenty-one out of 22 final usability objectives were achieved and the feasibility of Web-based vision screening was demonstrated.