Achromatopsia © 2025

Achromatopsia, also known as Rod monochromacy

It is a medical syndrome that exhibits symptoms relating to five conditions, most notably monochromacy. Historically, the name referred to monochromacy in general, but now typically refers only to an autosomal recessive congenital color vision condition. The term is also used to describe cerebral achromatopsia, though monochromacy is usually the only common symptom. The conditions include: monochromatic color blindness, poor visual acuity, and day-blindness. The syndrome is also present in an incomplete form that exhibits milder symptoms, including residual color vision. Achromatopsia is estimated to affect 1 in 30,000 live births worldwide. Causes, congenital malfunction of the visual phototransduction pathway.

Signs and symptoms

The five symptoms associated with achromatopsia are:

Color blindness – usually monochromacy
Reduced visual acuity – uncorrectable with lenses
Hemeralopia – with the subject exhibiting photophobia
Nystagmus
Iris operating abnormalities

The syndrome is typically first noticed in children around six months of age due to their photophobia 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 six to seven years of life – but remain near 20/200. Otherwise, the syndrome is considered stationary and does not worsen with age.

If the light level during testing is optimized, achromats may achieve corrected visual acuity of 20/100 to 20/150 at lower light levels, regardless of the absence of color. The fundus of the eye appears completely normal.

Achromatopsia can be classified as complete or incomplete. In general, symptoms of incomplete achromatopsia are attenuated versions of those of complete achromatopsia. Individuals with incomplete achromatopsia have reduced visual acuity with or without nystagmus or photophobia. Incomplete achromats show only partial impairment of cone cell function.

Inheritance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Cerebral achromatopsia

Cerebral achromatopsia is a form of acquired color blindness that is caused by damage to the cerebral cortex. Damage is most commonly localized to visual area V4 of the visual cortex (the major part of the colour center), which receives information from the parvocellular pathway involved in color processing. It is most frequently caused by physical trauma, hemorrhage or tumor tissue growth. If there is unilateral damage, a loss of color perception in only half of the visual field may result; this is known as hemiachromatopsia. Cerebral achromats usually do not experience the other major symptoms of congenital achromatopsia, since photopic vision is still functions.

Color agnosia involves having difficulty recognizing colors, while still being able to perceive them as measured by a color matching or categorizing task.

Terminology

Monochromacy: Complete lack of the perception of color in a subject, seeing only in black, white, and shades of grey.

Hemeralopia: Reduced visual capacity in bright light, i.e. day-blindness.

Nystagmus: Term to describe both normal and pathological conditions related to the oculomotor system. In the current context, it is a pathological condition involving an uncontrolled oscillatory movement of the eyes during which the amplitude of oscillation is quite noticeable and the frequency of the oscillation tends to be quite low.

Photophobia: Avoidance of bright light by those who have hemeralopia.

Description

Achromatopsia is a condition characterized by a partial or total absence of color vision. People with complete achromatopsia cannot perceive any colors; they see only black, white, and shades of gray. Incomplete achromatopsia is a milder form of the condition that allows some color discrimination.

Achromatopsia also involves other problems with 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 can also have farsightedness (hyperopia) or, less commonly, nearsightedness (myopia). These vision problems develop in the first few months of life.

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.