Figure 1 illustrates the interaction dendrogram for this model. The hierarchical cluster analysis placed IVS5+30C>T (WDR36), IVS8–53T>C (OPTN), and Met98Lys (OPTN) on the same branch, and their closer position in the diagram clearly showed that the three SNPs may have a synergistic interaction effect on modulating risk of POAG. IVS5+38T>G (OPTN) and IVS2+35A>G (MYOC) were on another branch, revealing an interaction between them. −491A>T (APOE) was located on a different remote branch, suggesting that this SNP may have less of a relationship with other SNPs. Here, OPTN is linked to open-angle glaucoma.