Cone rod dystrophy (CRD) is a group of inherited retinal dystrophies that affect up to 1 in 40000 people. As the name implies, this condition first affects the cone photoreceptors, and then the rods. This leads to progressive loss of central vision and photophobia early on, with night blindness and peripheral vision loss developing later in the disease. Cone dystrophy (CD) is a similar disease, however only the cones are affected and thus patients retain their night and peripheral vision. Like in retinitis pigmentosa, there are many genes that can cause CRD and CD, and as a result the disease may be inherited in different patterns depending on the gene. As well, the severity of these diseases varies significantly between patients depending on their inheritance pattern and specific mutations.