In addition, direct retinal affection in PD has been already been described, and some of the sleep and visual alterations have been proposed as early biomarkers related to the degeneration of retinal dopaminergic amacrine (DA) cells [15] and intrinsically photosensitive retinal ganglion cells [16], or to the accumulation of phosphorylated alpha-synuclein, similar to Lewy bodies, in the retina [17, 18]. The gene discussed is SNCA; the disease is Parkinson disease.