The main aim of this study was to design, develop and test the instructional effectiveness of a web-based English vocabulary drill program developed for visually impaired middle school students. In this respect, the study focused on the educational affordances of the program and its contribution on VI students' spelling and semantics knowledge in English vocabulary. Depending on the purpose and the nature of the study, exploratory case study and single-subject research were implemented. Face-to-face intervention sessions were applied from October 2015 through to February 2016. There were two groups of participants in the study, which were students and experts. The data were collected through interviews, vocabulary and retention tests. Collected data were analyzed with both qualitative and quantitative data analysis techniques. Based on the qualitative data analysis, educational affordances of the web-based drill program were identified as instantaneous access to content, individualized instruction and tracking progress. Quantitative findings revealed that students showed substantial progress on the vocabulary tests and maintained their achievements after the study.