Achromatopsia

Achromatopsia is a disorder that causes problems with color vision. The retina, which is the light-sensitive tissue at the back of the eye, contains two types of light receptor cells called rods and cones. Rods provide vision in low light (night vision), while cones provide vision in bright light (daytime vision). Cones are also responsible for color vision. 

There are two types of achromatopsia: complete and incomplete. People with complete achromatopsia cannot perceive any color; they see only black, white, and shades of gray. People with incomplete achromatopsia can see some color.

People with achromatopsia may have additional problems with their vision, including an increased sensitivity to light and glare (photophobia), involuntary back-and-forth eye movements (nystagmus), and significantly reduced sharpness of vision (low visual acuity). Affected individuals may also have a small visual blind spot (scotoma), farsightedness (hyperopia), or nearsightedness (myopia).

Achromatopsia is different from the more common forms of color vision deficiency (also called color blindness), in which people can perceive color but have difficulty distinguishing between certain colors, such as red and green. One form of color blindness, called blue cone monochromacy (BCM), is sometimes considered a form of incomplete achromatopsia.