The effect of visual feedback of body parts on pain perception: A systematic review of clinical and experimental studies

Background and Objective: The aim of this systematic review was to evaluate the effect of visual feedback techniques on pain perception by analysing the effect of normal-sized, magnified or minified visual feedback of body parts on clinical and experimentally-induced pain. Databases and Data Treatment: Databases searched: Medline, Embase, PsychInfo, PEDro, CINAHL, CENTRAL and OpenSIGLE. Studies investigating pain patients and pain-free participants exposed to experimentally-induced pain were analysed separately. Risk of bias was assessed and data meta-analysed. Results: 34 studies were included. A meta-analysis of clinical data favoured mirror visual feedback (6 trials; mean difference=-13.06mm; 95%CI -23.97, -2.16). Subgroup analysis favoured mirror visual feedback when used as a course of treatment (3 trials; mean difference=-12.76mm; 95% CI -24.11, -1.40), and for complex regional pain syndrome (3 trials; standard mean difference=-1.44; 95%CI -1.88, -0.99). There is insufficient evidence to determine differences between normal-sized view and a size-distorted view of the limb. Mirror visual feedback was not superior to object view or direct view of the hand on reducing experimental pain in pain-free participants. There were inconsistencies in study findings comparing normal-sized reflection of a body part and a reflection of an object, or a magnified or minified reflection. Conclusions: There is tentative evidence that mirror visual feedback can alleviate pain when delivered as a course of treatment, and for patients with complex regional pain syndrome. It was not possible to determine whether normal-sized, magnified or minified visual feedback of body parts affects pain perception because of contradictory findings in primary studies.