RSPO2 and optic atrophy: Associated loci include; rs10762201 and rs2004187 near the ATOH7 and IRX2 genes respectively, both associated with eye development [36, 37]; rs79833181 near NBAS associated with optic atrophy [38]; rs149831820 near ROBO2 associated with retinal ganglion cell axon guidance [39, 40]; and rs73348111 (at IKZF1), rs13271359 and rs376067714 (both at RSPO2) involved in differentiation and retinal cell definition [41, 42].