Neck movement limitations and the use of head-operated computer controls for people with disabilities

Use of a standard computer mouse is difficult or impossible for many people with disabilities who have limited use of their upper extremities. One alternative is a head control interface, which allows a person to use head movements to operate a computer. However, disabilities that limit movement of the upper extremities may also limit a person's ability to move his or her neck. Such neck movement limitations may reduce a person's ability to effectively use head controls. A method by which head controls can be adapted to the abilities and limitations of an individual user would be beneficial for individuals with neck movement limitations.; In a study of ten subjects with either multiple sclerosis or spinal cord injuries and fifteen subjects without disabilities, reduced neck range of motion was found to be correlated with reduced accuracy and speed in computer exercises. Five methods of compensating for neck movement limitations were then evaluated in comparison to a standard head control interface. Twenty-two subjects without disabilities and three subjects with multiple sclerosis performed icon acquisition exercises. Subjects tended to be more accurate when head control sensitivity was increased, and faster when sensitivity was reduced. Subjects were less likely to overshoot icons when using head movements to control cursor velocity rather than cursor position.; Based on these results, software was developed to measure a person's performance with a head control system and automatically adjust to the user's limitations. This software was associated with improved speed in controlled exercises involving sixteen subjects with spinal cord injury or multiple sclerosis. Five current head control users evaluated the software in a real-world setting. Only one of these five subjects perceived an improvement in comparison to his current head control system.; A person's ability to operate a computer is related to both the characteristics of the computer interface device and the user's abilities and limitations. This study provides insight into these relationships in the context of head-operated controls for people with disabilities. A better understanding of these relationships will assist in the design and adjustment of head controls. This study also provides evidence that computer interface software can automatically adjust to the needs of users with disabilities, based on the user's performance. These research outcomes will contribute to making computers accessible to a larger population, thus increasing people's independence and quality of life.