Cone dystrophy: A disease of the cones, the specialized light-sensitive cells that act as photoreceptors in the retina of the eye, providing sharp central vision and color vision. The cone dystrophies are a form of genetic macular degeneration characterized by progressive deterioration of the cones that leads to the distinctive triad of loss of color vision, photophobia, and reduced central vision. Cone dystrophy genes have been mapped to chromosome regions 6p21.1, 6q25-q26, 17p12-13, and Xp21.1-p11.3. In region 6p21.1, mutations have been found in the gene that encodes GCAP1, a key component in the recovery of photoreceptor cells to the dark-adapted state after exposure to a light stimulus.