Congenital red–green color blindness
| Congenital red–green color blindness | |
|---|---|
| Other names | Daltonism; red–green color vision deficiency |
| An example Ishihara test that may be used to detect red–green color blindness. Those with normal color vision should be able to see a green "74" on an orange background. Those with red–green color blindness may see the number "21" or no number at all, with the green and red hues appearing much more similar, if not indistinguishable. | |
| Specialty | Ophthalmology |
| Symptoms | Reduced color distinction along red-green axis |
| Usual onset | Congenital |
| Duration | Lifelong |
| Causes | Genetic (inherited, usually X-linked) |
| Diagnostic method | Color vision tests |
| Differential diagnosis | Acquired red–green color blindness |
| Treatment | None |
| Medication | None |
| Frequency | 2-9% males; <1% females |
Congenital red–green color blindness is an inherited condition that is the root cause of the majority of cases of color blindness. It has no significant symptoms aside from its minor to moderate effect on color vision. It is caused by variation in the functionality of the red and/or green opsin proteins, which are the photosensitive pigment in the cone cells of the retina, which mediate color vision. Males are more likely to inherit red–green color blindness than females, because the genes for the relevant opsins are on the X chromosome. Screening for congenital red–green color blindness is typically performed with the Ishihara or similar color vision test. It is a lifelong condition, and has no known cure or treatment.
This form of color blindness is sometimes referred to historically as daltonism after John Dalton, who had congenital red–green color blindness and was the first to scientifically study it. In other languages, daltonism is still used to describe red–green color blindness, but may also refer colloquially to color blindness in general.