Understanding Red-Green Colorblindness: A Misnomer Explained

The term 'colorblind' is often a misnomer, as it suggests a complete inability to see colors. In reality, many people with red-green colorblindness can distinguish between red and green to some extent. This article delves into the intricacies of red-green colorblindness, explaining its various types and the factors that influence color vision.

What is Red-Green Colorblindness?

The more accurate term for red-green color vision deficiency is 'color vision deficiency.' Red-green colorblindness comes in various 'flavors,' with each flavor being a result of abnormalities in the long-wave (L) or mid-wave (M) cones of the eye. These abnormalities can range from mild to strong, and in some cases, the cone may be entirely non-functional, leading to total red-green colorblindness (deuteranopia).

Understanding the Types of Red-Green Colorblindness

There are 8 types of red-green colorblindness. Four of these types are due to abnormalities in the long-wave (L) cones, while the other four are due to abnormalities in the mid-wave (M) cones. The 'abnormality' can be mild, moderate, or strong, indicating how much the spectral peak of the cones is shifted from its 'proper place.'

A notable result of this shift is the reduction in the 'red-greeness' of colors, a phenomenon known as 'dilution.' This can be observed in the graph of normal cone responses, which shows the spectral shifts for the M and L cones in mild, moderate, and strong cases.

Personal Experience and Learning to Differentiate

For individuals with red-green colorblindness, the ability to differentiate between red and green colors is not complete. A person with mild deuteranomaly, for instance, may see red and green as pushed towards yellow, with red appearing more orange and green appearing as a 'lime green.' This is often a result of learning to differentiate through daily experiences rather than being inherently colorblind.

Kevin and Coty, two individuals with different types of red-green colorblindness, exemplify this. Kevin has deuteranopia (non-functional M cone), while Coty has deuteranomaly. Each individual may perceive colors differently, with Kevin experiencing total red-green colorblindness and Coty experiencing a more moderate form where colors are somewhat mixed or appear faint.

Testing and Diagnosis

Testing for red-green colorblindness includes various methods, with the Enchroma test being a popular one. Videos and other online resources can provide detailed information on these tests.

Armed Forces and Selection Tests

Armed forces use color vision tests to determine whether individuals can distinguish red and green dots under various conditions, especially on a murky day. If a person is unsure about their color vision, they can opt for a Lantern test. This test is commonly used in the United Kingdom during selection processes, as the Ishihara test, a screening test, requires good lighting conditions.

Visual Simulations

To better understand the visual experience of someone with different types of red-green colorblindness, visual simulations can be used. These simulations show how normal color vision, mild deuteranomaly, deuteranopia, monochromacy (complete color blindness), and achromatopsia (a form of monochromacy) differ from each other.

Conclusion

Red-green colorblindness is not a single condition but a collection of various types, each with its own set of characteristics and visual experiences. While the term 'colorblind' might imply a complete inability to differentiate colors, it is important to understand the nuances of color vision deficiency and how it can affect individuals differently.