Absence of vision from birth induces a hypersensitivity to painful stimuli, lending new support to a model of sensory integration of vision and pain processing.
Vision is important for avoiding encounters with objects in the environment that may imperil physical integrity. We tested whether, in the absence of vision, a lower pain threshold would arise from an adaptive shift to other sensory channels. We therefore measured heat and cold pain thresholds and responses to suprathreshold heat stimuli in 2 groups of congenitally blind and matched normal-sighted participants. We also assessed detection thresholds for innocuous warmth and cold, and participants’ attitude toward painful encounters in daily life. Our results show that, compared to sighted subjects, congenitally blind subjects have lower heat pain thresholds, rate suprathreshold heat pain stimuli as more painful, and have increased sensitivity for cold pain stimuli. Thresholds for nonpainful thermal stimulation did not differ between groups. The results of the pain questionnaires further indicated that blind subjects are more attentive to signals of external threats. These findings indicate that the absence of vision from birth induces a hypersensitivity to painful stimuli, lending new support to a model of sensory integration of vision and pain processing.
aChaire de recherche Harland Sanders en Sciences de la vision, École d’Optométrie, Université de Montréal, Montréal, Québec, Canada
bBRAINlab, Department of Neuroscience and Pharmacology, Panum Institute, University of Copenhagen, Copenhagen, Denmark
cLaboratory of Clinical Biochemistry and Molecular Biology, University of Pisa Medical School, Pisa, Italy
*Corresponding author. Address: BRAINlab, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences—Panum Institute, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark. Tel.: +45 24959624.
Submitted January 30, 2013; revised May 17, 2013; accepted May 20, 2013.