The process of vision involves two stages; the retinoid cycle which supplies and regenerates the visual chromophore required for vision and phototransduction which propagates the light signal. Defects in the genes involved in the retinoid cycle cause degenerative retinal diseases. These defective genes are described here (for reviews see Travis et al. 2007, Palczewski 2010, Fletcher et al. 2011, den Hollander et al. 2008).