These 13 glaucoma-associated genes can be divided into three functional groups: phototransduction-related genes (GNGT1, OPN1SW, PDE6A, PDC, CRX, CNGB1, GUCY2F), glutamate receptor (GR) genes (GRIN2B, GRIK3, GRIK4), and 5-hydroxytryptamine receptor (HTR) genes (HTR1A, HTR1E, HTR7). The gene discussed is GRIK4; the disease is glaucoma.