Cone-rod dystrophy results from a primary loss of cone photoreceptors, followed by loss of rods.
Cone-rod retinal dystrophy characteristically leads to early impairment of vision. An initial loss of color vision and of visual acuity (due to loss of cone function) is followed by nyctalopia (night blindness) and loss of peripheral visual fields (due to loss of rod function). In extreme cases, these progressive symptoms are accompanied by widespread, advancing retinal pigmentation and chorioretinal atrophy of the central and peripheral retina. For related but different diseases, see Achromatopsia, Cone Dystrophy and Rod-Cone Dystrophy.