Summary
Highlights
Most individuals have trichromatic color vision due to three fully functioning color cones. However, color blindness, especially red-green color deficit, is quite common. The video starts by discussing John Dalton's famous case of color blindness, where he described seeing only yellow, blue, and purple. Later gene testing confirmed he was a deuteranope, missing the green cone pigment, making him a dichromat. This severe form of color blindness made 'daltonism' a historical term for the condition.
Color deficiency primarily occurs at two levels. The simplest is when an entire cone class is missing, leading to dichromatic vision. For instance, missing green cones results in red-green color deficiency, as seen in Dalton's case. The second, more complex level, involves the presence of a hybrid or chimeric cone pigment instead of a properly functioning one. This results in anomalous trichromacy, where color sensitivity can range from near-normal to severe, mimicking a dichromatic state.
The video then explores monochromatic vision. Rod monochromats, who have only rods and no cones, see the world in grayscale, suffer from poor acuity due to the lack of cones in the fovea, and struggle in bright light. Cone monochromats, having only one type of cone, also see in grayscale, differentiating only brightness. Their visual acuity depends on which cone type is present; blue cone monochromat vision is poorer as there are no blue cones in the central fovea.
Dichromats possess two types of cones. Examples include protanopia (missing red cones), resulting in a blue-yellow color palette due to the color opponent process. Deuteranopia (missing green cones) and protanopia fall into the red-green deficiency category, offering similar visual outcomes. Tritanopia (missing blue cones) results in blue-yellow deficiency. The video highlights that many mammals, such as dogs and cats, are dichromats with S and L pigments.
Anomalous trichromats have three cones, but one is a hybrid, causing varying degrees of color deficit. Simulating this condition is more complex than dichromacy as it involves a shift in cone sensitivity and the color opponent system. The video references research that attempts to physiologically reproduce likely color vision results for varying levels of protanomaly and deuteranomaly, comparing them to normal vision and full dichromacy.
The video provides statistics on the prevalence of different color deficiencies, noting that red or green cone deficiencies occur in about 1% of males for dichromats, and red-green deficits in anomalous trichromats affect about 8% of males (1 in 12). Finally, it underscores the increased attention designers are now paying to color choices in graphics and web page layouts to accommodate individuals with color blindness, offering useful color choices.