RGR and retinoschisis: Mutations in the PDE6C gene cause recessive cone dystrophy (OMIM: 613093), which is characterized by early-onset decreases in visual acuity, impaired color vision, central vision loss, and photophobia.[34] Mutations in the RS1 gene cause retinoschisis (OMIM: 300839).[35] Levels of rhodopsin (RHO) and retinal G-protein coupled receptor (RGR) were highest in the juxta-macular retina (Table 1).