While, as expected, morphine induced statistically significant mydriasis (pupil dilation) after resection, NalM-treated mice and MOR-KO mice displayed significant higher miosis (pupil contraction) compared to control condition (before resection), reflecting an increased nociceptive sensitivity for NalM and MOR-KO groups of animals (Fig. 1d, e and Table 1). This evidence concerns the gene OPRM1 and Mydriasis.