This study proposed a single-switch text entry system by hierarchical scanning of character strokes for an 11-year-old girl with severe physical disabilities and low vision. She could only perceive magnified straight line segments and chords presented against high-contrast, colored backgrounds. In a descriptive case study, the participant used the proposed system in the community for 8 months. Assessment included theoretical evaluation of text entry performance and empirical evaluation of the participant's proficiency. The proposed system had a lower error-free text entry rate but comparable proneness to user error as a real-world implementation of row-column virtual scanning keyboard with character frequency layout. The participant's proficiency, in terms of mean number of single-switch activations and time to type one character, showed statistically significant improvements as the case study progressed. The proposed system feasibly addressed the participant's typing needs, in a context where traditional row-column scanning and codeword-based text entry systems were not successful.
- cerebral palsy
- character stroke disambiguation
- cortical visual impairment
- single-switch scanning
- text entry