MMP9 and Norrie disease: Although the nine variants in apoptotic‐relevant genes were not associated with ND and functional outcome by univariate analysis, GMDR analysis revealed that there was a gene–gene interaction among P53 rs1042522, MDM‐2 rs2279744, and MMP‐9 rs3918242, and the high‐risk interaction among the three variants was independently associated with higher risk of ND and poor functional outcome.