Achromatopsia (ACHM) is a medical syndrome that exhibits symptoms relating to at least five separate individual diseases. Although the term may refer to acquired disorders such as color agnosia and cerebral achromatopsia, it typically refers to an autosomal recessive congenital color vision disorder, 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.

Alternative Names of Achromatopsia are: Cerebral Achromatopsia, total color blindness, congenital cone dysfunction, color blindness total, day blindness, monochromatism, Rod monochromatism, Achromatopia.

Complications of Achromatopsia

Complications and sequelae of Achromatopsia from the Diseases Database include:

• Colour vision impairment.
• Nystagmus.
• Photophobia.

Causes of Achromatopsia

Acquired Achromatopsia

• 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).
• Thalamic achromatopsia/dyschromatopsia is caused by damage to the thalamus, a portion of the brain stem. 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.

Congenital Achromatopsia

The known causes of the congenital forms of achromatopsia are all due to malfunction of the retinal phototransduction pathway. Specifically, this form of ACHM seems to result from the inability of cone cells to properly respond to light input by hyperpolarizing. Known genetic causes of this are mutations in the cone cell cyclic nucleotide-gated ion channels CNGA3 (ACHM2) and CNGB3 (ACHM3) as well as the cone cell transducin, GNAT2 (ACHM4).

Signs & Symptoms of Achromatopsia

The five symptoms associated with achromatopsia/dyschromatopsia are:

• Achromatopia
• Amblyopia (reduced visual acuity)
• Hemeralopia (with the subject exhibiting photophobia)
• Nystagmus
• Iris operating abnormalities

A sixth symptom associated with achromatopsia/dychromatopsia is seldom reported. Many sufferers are unaware of the three-dimensional aspect of their visual system. They frequently fail to observe any of the stereographic features of a scene.

The syndrome is frequently noticed first in children around six months of age by their photophobic activity and/or their nystagmus. The nystagmus becomes less noticeable with age but the other symptoms of the syndrome become more relevant as school age approaches. Visual acuity and stability of the eye motions generally improve during the first 6–7 years of life (but remain near 20/200). The congenital forms of the disease are considered stationary and do not worsen with age.

Complete Achromatopsia

Aside from a complete inability to discriminate colors, individuals with complete achromatopsia have a number of other ophthalmologic aberrations. Included among these aberrations are greatly decreased visual acuity (<0.1 or 20/200) in daylight Hemeralopia, nystagmus, and severe photophobia. The fundus of the eye appears completely normal.

Incomplete Achromatopsia (Dyschromatopsia)

In general, symptoms of incomplete achromatopsia are similar to those of complete achromatopsia except in a diminished form. Individuals with incomplete achromatopsia have reduced visual acuity with or without nystagmus or photophobia. Furthermore, these individuals show only partial impairment of cone cell function but again have retained rod cell function.

Treatments of Achromatopsia

There is generally no treatment to cure achromatopsia. However, since 2003, there is a cybernetic device called eyeborg that allows people to perceive colour through sound waves.

Prevention of Achromatopsia

In general, there is no way to prevent color blindness. Regular eye exams and prompt treatment of eye disorders may help prevent some cases of color blindness.