Achromatopsia

Achromatopsia: a very rare color deficiency in which the colors of the spectrum are seen only as shades of white, gray, and black; can be either incomplete color blindness (blue-cone monochromatism, an X-linked recessive disorder where only the blue cones and the rods are funtioning properly; characterized by reduced visual acuity and sometimes also photophobia and nystagmus) or complete color blindness (rod monochromatism or total color blindness, an autosomal recessive disorder where no cones are functioning and only rods are functioning properly; characterized by reduced visual acuity, photophobia, and nystagmus.