Acquired achromatopsia/dyschromatopsia is a condition associated with damage to the diencephalon (primarily the thalamus of the mid brain) or the cerebral cortex (the new brain), specifically the fourth visual association area, V4 which receives information from the parvocellular pathway involved in colour processing.

Thalamic achromatopsia/dyschromatopsia is caused by damage to the thalamus; it is most frequently caused by tumor growth since the thalamus is well protected from external damage.

Cerebral achromatopsia is a form of acquired color blindness that is caused by damage to the cerebral cortex of the brain, rather than abnormalities in the cells of the eye's retina. It is most frequently caused by physical trauma, hemorrhage or tumor tissue growth.

Achromatopsia (ACHM), also known as total color blindness, is a medical syndrome that exhibits symptoms relating to at least five conditions. The term may refer to acquired conditions such as cerebral achromatopsia, also known as color agnosia, but it typically refers to an autosomal recessive congenital color vision condition, the inability to perceive color and to achieve satisfactory visual acuity at high light levels (typically exterior daylight). The syndrome is also present in an incomplete form which is more properly defined as dyschromatopsia. It is estimated to affect 1 in 40,000 live births worldwide.

There is some discussion as to whether achromats can see color or not. As illustrated in "The Island of the Colorblind" by Oliver Sacks, some achromats cannot see color, only black, white, and shades of grey. With five different genes currently known to cause similar symptoms, it may be that some do see marginal levels of color differentiation due to different gene characteristics. With such small sample sizes and low response rates, it is difficult to accurately diagnose the 'typical achromatic conditions'. If the light level during testing is optimized for them, they may achieve corrected visual acuity of 20/100 to 20/150 at lower light levels, regardless of the absence of color. One common trait is hemeralopia or blindness in full sun. In patients with achromatopsia, the cone system and fibres carrying color information remain intact. This indicates that the mechanism used to construct colors is defective.