Blue cone monochromatism is an inherited vision disorder. In this condition, the light sensitive cells in the eye used for color vision (cones) are affected. There are three types of cones that respond to one of three colors: red, green, and blue. When people have Blue cone monochromatism, both the red and green cones do not function properly, while the blue cones work normally. Signs and symptoms may include impaired color vision, low visual acuity (clarity or sharpness), photophobia (light sensitivity), myopia (nearsightedness), and nystagmus (fast, uncontrollable movements of the eye). Blue cone monochromatism is caused by genetic changes in either the OPN1LW or the OPN1MW gene(s) and is inherited in an X-linked manner.