The term color blindness is generally used to refer to instances where people have difficulties observing the contrast between different colors. Often this will be the difference between two specific colors – a famous example of this being Mark Zuckerberg who designed the Facebook entirely in blue due to a red-green color blindness. This is the most common form of color blindness, though there are many others and many other causes.
Unfortunately there is no ‘cure’ for this form of color blindness and it is something that many people live with. Though this is classed as a mild disability and excludes those with the condition from some careers, it is also believed that there may be some evolutionary advantage to color blindness and red-green ‘deuteranomaly’ in particular. Deuteranomaly is caused by a slight shift in the green cones (cones perceive color) that places them nearer to the red cones (in spectral sensitivity) and makes them more difficult to differentiate – as this is caused by a recessive gene and is predominant in 5% or more of the male population it is believed that there must be some kind of evolutionary advantage. In fact studies have demonstrated that those with deuteranomaly may be better able to see camouflage that would fool those with normal vision. Of course this could be highly useful in the wild.
There are in fact though several different forms of inherited color blindness and other ‘color vision deficiencies’. These include:
Or total color blindness and lack of ability to distinguish between any colors. This is caused by a defect in all cones or even an absence of all cones. Rod monochromacy is the term for a lack of rods and is highly rare and causes other vision problems such as photophobia (sensitivity to light), whereas cone monochromacy is relatively normal vision other than complete color blindness.
This is moderate to severe color vision defect as a result of one pigment being missing. Normally there are three pigment cones and it is from these that we make up all other colors. If one of these cones is missing or damaged, then vision is reduced to two color dimensions. In protanopia there is no red receptors, in deuteranopia there is no green and in tritanopia there are no blue. These forms of color blindness effect far more than just one color however, as that color is used to perceive a range of other colors.
This is a form of inherited color blindness which is caused by the sensitivity of one of the three cones being damaged. For instance our previous example of deuteranomaly is caused by green receptors being too close to the red. Similarly in protanomaly the spectral sensitivity of the red cones is altered to be more similar to the green. In tritanomaly the blue-yellow cones are too similar. Interestingly, while other forms of color blindness are more common in males, tritanomaly has no gender preference.
In some rare cases it may be possible for women to have four types of cones as a result of heterozygous anomalous trichromacy thanks to X-chromosome inactivation. In theory they would have greater color vision with an extra dimension.
Despite these apparent benefits of color blindness it is still largely perceived as a disability and many would still rather not live with the condition. While there is no ‘cure’ there are some treatments that can make the conditions less noticeable which depend on the kind of color vision impairment. These are as follows:
• In the case of acquired color blindness which can occur through injury or trauma, it may be possible to repair the problem using surgery.
• For a range of color blindnesses such as deuteranomaly, tinted contact lenses or glasses can help to increase the contrast between similar colors and thereby help you to better perceive the differences. However they may also distort some objects.
• In the case of rod monochramacy the individual has only rods and no cone receptors. This means that they are unable to see color, and will also be sensitive to light as normally we use our rods for night vision (which is why we see little color at night). Tinted glasses then won’t help to restore any color vision, but they can help to improve general vision and decrease photosensitivity.
• Glasses that block glare might also be useful for a number of color vision problems as glare and brightness can prevent you from seeing color as easily.
• There is also a psychological element to color blindness and it may be possible to train yourself to better differentiate between colors by testing yourself and checking your answers. This will get you more accustomed to noticing the slight differences and make them appear more clear more quickly. Studies have found interesting results regarding our ability to differentiate colors – in cultures where there are fewer color terms and those individuals have grown up without differentiating between certain hues they are actually physically unable to distinguish between those different colors. Other than red, blue and green then, it would seem that color terms are very much arbitrary.
• Finally research is being done into permanent cures for color blindness which are looking promising. These include the use of genetic modifications to re-enable certain codes and it appears that the brain is plastic and adaptable enough to adapt to these changes. In one study monkeys with color blindness had their full vision completely restored and it is believed the same technique would work on humans.