Here we addressed the question if impaired residual vision affects asymmetry in hand use in right-handed blind subjects. Getting blind requires finding new strategies for interaction with the environment. We therefore expected changes in hand use in subjects with impairer vision.
We used three types of assessment of hand use: A modified Edinburgh questionnaire to detect the subjective hand preference, a tapping task to provide insight in how dexterity is affected, and an objective measure of the frequency of hand use during activities of daily living recorded with acceleration sensors.
All subjects tested indicated that their preferred hand was right. The subjective rating was positively correlated with their performance in the motor task. In addition, we found a positive correlation between right hand superiority in the specific motor task and residual vision. The more residual vision the subject had, the more superiority was present in the right hand. Surprisingly, the hand usage during daily living was correlated neither with the subjective hand preference nor with the preference observed in the motor task. This discrepancy suggests that most blind subjects are unaware of the changes in hand dominance that occur during the process of impairment of vision.