Momentary improvement of hand sensibility by excluding vision

The aim of this study was to investigate the effects of visual input on the results in a sensory testing procedure on hands. Sensory testing was done with the tested hand behind a screen in a counterbalanced setting with open eyes, and blindfolded in 66 healthy persons. Tactile discrimination (2pd) and touch thresholds (Semmes-Weinstein monofilaments) were tested for on the index finger of the dominant hand. Tactile discrimination was significantly better when the test subject was blindfolded than when eyes were open. Our results showed that removal of all visual input during sensibility testing gave improved results compared with testing with visual input (opened eyes but the hand out of sight). The mechanism behind the improvement is probably rapid changes in the brain. Manipulation of visual input during sensibility testing, particularly during tests that include an element of interpretation, influences the test result. These results highlight the importance of standardised procedures in sensibility testing.