Achromatopsia

Achromatopsia, also known as rod monochromacy, is an inherited disorder of color vision in which a person sees the world only in shades of gray, typically alongside poor visual acuity, sensitivity to bright light and day blindness. It is usually passed on in an autosomal recessive pattern and arises from a congenital malfunction of the visual phototransduction pathway, the process by which light striking the retina is converted into a nerve signal. A milder, incomplete form of the condition leaves some residual color vision. The disorder is diagnosed using electroretinography, which measures the retina's electrical response to light, and it is estimated to affect roughly one in thirty thousand people worldwide. The term has historically also been used more loosely for monochromacy in general, including a separate condition caused by brain injury rather than the eye itself.