The dopaminergic amacrine cells couple to melanopsin-sensitive retinal ganglion cells in the GCIPL, and immunohistochemistry shows that reduced dopaminergic plexi in individuals with PD are accompanied by abnormal retinal ganglion cell morphology.34 Immunohistochemical staining for dopamine was almost absent from the INL in PD. The gene discussed is OPN4; the disease is Parkinson disease.