chromatismus

Chromatismus, commonly referred to as color vision deficiency, is a partial or complete inability to distinguish colors accurately. It can be congenital, present from birth, or acquired later in life due to disease, injury, or certain medications. The condition ranges from mild color confusion to total color blindness, with various patterns of impairment.

The most common forms are congenital red-green deficiencies, caused by alterations in the cone photoreceptors in the retina. These include protanopia and deuteranopia (complete inability to perceive red or green) and their less severe forms, protanomaly and deuteranomaly. Blue-yellow deficiencies, such as tritanopia and tritanomaly, occur less frequently. Rarely, individuals have complete achromatopsia or monochromacy, where color perception is absent. Congenital chromatismus is typically inherited in an X-linked manner, explaining a higher prevalence in males.

Acquired chromatismus can result from ocular or optic nerve diseases (for example glaucoma, optic neuritis, or retinal pathology), systemic conditions, or medications with retinal toxicity (such as certain antimalarials or chemotherapeutic agents). Age-related changes can also contribute to diminished color discrimination.

Diagnosis relies on specialized testing. Screening tests like the Ishihara plates assess red-green discrimination, while more detailed evaluations use the Farnsworth-Munsell hue tests or an anomaloscope to quantify hue matching. Genetic testing may be offered in some cases to determine inheritance patterns.

There is no cure for most congenital color vision deficiencies, but many individuals adapt through color labeling, memorization, and safety practices. Assistive devices and color-identification apps or tinted lenses may aid specific tasks, though effectiveness varies by type and severity. The condition generally does not affect overall vision or health beyond color perception.