Description
Color blindness, also known as color vision deficiency, is a condition that affects the perception of colors. While most people can differentiate between a wide range of colors, individuals with color blindness have difficulty distinguishing certain colors or perceiving them as they appear to those with normal vision.
In this article, we will explore the different types of color blindness, their effects on color perception, prevalence, and coping mechanisms.
Color blindness is a visual impairment that can be present from birth or acquired later in life due to certain medical conditions or medication side effects.
Understanding the various types of color blindness is crucial to creating inclusive environments and providing support to those who experience these challenges.
Normal Vision And Color Perception
To comprehend color blindness, it is essential to grasp how the human eye perceives colors. The eye contains specialized cells called cones, which are responsible for detecting and interpreting different colors.
Cones are particularly sensitive to three primary colors: red, green, and blue. When these cones work harmoniously, we experience the vast spectrum of colors in our surroundings.
Trichromacy
Normal color vision uses all three types of cone cells which are functioning correctly. Another term for normal color vision is trichromacy. People with normal color vision are known as trichromats.
Anomalous Trichromacy
People with ‘faulty’ trichromatic vision will be color blind to some extent and are known as anomalous trichromats. In people with this condition, all of their three cone cell types are used to perceive light wavelengths but one type of cone cell perceives light slightly out of alignment.
There are three different types of effect produced depending upon which cone cell type is ‘faulty’ and there are also different severities.
The different anomalous condition types are protanomaly, which is a reduced sensitivity to red light, deuteranomaly which is a reduced sensitivity to green light (the most common form of color blindness), and tritanomaly which is a reduced sensitivity to blue light (extremely rare).
The effects of anomalous trichromatic vision can range from almost normal color perception to almost total absence of perception of red, green, or blue light.
People with deuteranomaly and protanomaly are often incorrectly diagnosed collectively as ‘red-green’ color blind because both types generally have difficulty distinguishing between reds, greens, browns, and oranges.
They also commonly confuse different types of blue and purple hues and many other color combinations.
People with reduced blue sensitivity have difficulty identifying differences between blue and yellow, violet and red, and blue and green. To people with blue deficiencies, the world appears as generally red, pink, black, white, grey, and turquoise.
See the dichromacy images below – about half of people with anomalous trichromacy will see the world in a similar way to those with dichromacy but their ability to perceive colors may improve in good light and deteriorate in poor light.
Often their color perception can be as poor as it is for those with dichromacy. Many other people with anomalous dichromacy (those with mild color vision deficiency) will have fewer problems discriminating between colors.
People with anomalous dichromacy may either have inherited color blindness, in which case their ability to see colors will remain the same, or they may have acquired it, in which case their condition could get worse, or possibly improve over time.
Dichromacy
People with dichromatic color vision have only two types of cone cells that are able to perceive color i.e. they have a total absence of function of one cone cell type, resulting in a specific section of the light spectrum that can’t be perceived at all.
For convenience, we call these areas of the light spectrum ‘red’, ‘green’, or ‘blue’. The sections of the light spectrum that the ‘red’ and ‘green’ cone cells would normally perceive overlap significantly, so people with red and green types of color blindness experience many similar color confusions.
This is why red and green color vision deficiencies are often known as red/green color blindness and why people with red and green deficiencies often see the world in a similar way.
People with protanopia are unable to perceive any ‘red’ light, those with deuteranopia are unable to perceive ‘green’ light and those with tritanopia are unable to perceive ‘blue’ light.
People with both red and green deficiencies live in a world of murky greens where blues and yellows stand out. Browns, oranges, and shades of red and green are easily confused and people with both types will also confuse some blues with some purples and struggle to identify pale shades of most colors.
However, there are some specific differences between the two types of red/green deficiencies.
Protanopia
Protanopes are more likely to confuse:-
1. Black with many shades of red
2. Dark brown with dark green, dark orange, dark red, dark blue/purple, and black
3. Some blues with some reds, purples, and dark pinks
4. Mid-greens with some oranges
Deuteranopes
Deuteranopes are more likely to confuse:-
1. Mid-reds with mid-greens
2. Blue greens with grey and mid-pinks
3. Bright greens with yellows
4. Pale pink with light grey/white
5. Mid-reds with mid-brown
6. Light blues with lilac
Tritanopes
The most common color confusions for tritanopes are light blues with greys, dark purples with black, mid-greens with blues, and oranges with reds.
The images above show how the beautiful colors of the pigments are lost to people with each type of dichromatic vision.
Monochromacy (achromatopsia)
People with monochromatic vision can see no color at all and their world consists of different shades of grey ranging from black to white, rather like seeing the world on an old black-and-white television set.
Achromatopsia is a specific eye condition that people see in greyscale. We do not specifically support achromatopsia because of its additional symptoms.
Achromatopsia is extremely rare, occurring only in approximately 1 person in 33,000 and its symptoms can make life very difficult. Usually, someone with achromatopsia will need to wear dark glasses inside in normal light conditions.
We occasionally have had very concerned people contact us because they or their children have been diagnosed by their optician with ‘total color blindness’.
Although we are unable to advise on the diagnosis of specific cases we have undertaken further research to try and understand why so many people are being told they are totally color blind when in reality they are much more likely to have a severe form of red-green color blindness.
Our research has revealed that in many cases optometrists receive only very basic training on color vision deficiency and some may therefore be incorrectly interpreting the results of the Ishihara tests.
The Ishihara test cannot diagnose either blue/yellow or ‘greyscale’ vision. If you/your child has been diagnosed only using the Ishihara test please seek a second opinion, ideally at a specialist color vision clinic.
Statistics
There is general agreement that worldwide 8% of men and 0.5% of women have a red/green type of color vision deficiency.
These figures rise in areas where there is a greater number of white (Caucasian) people per head of population, so in Scandinavia, the figures increase to approximately 10-11% of men.
By contrast, in sub-Saharan Africa, there are few color-blind people. Countries such as India and Brazil have a relatively high incidence of CVD because of the large numbers of people with mixed-race genes in their genetic history.
The 8% of color-blind men with inherited color blindness can be divided approximately into 1% deuteranopes, 1% protanopes, 1% protanomalous, and 5% deuteranomalous.
Approximately half of the color-blind people will have a mild anomalous deficiency, the other 50% have moderate or severe anomalous conditions.
The numbers of tritanopes/tritanomalous people and achromats are very small, perhaps 1 in 30-50,000 people.
Reliable statistics for people with an acquired form of color vision deficiency are difficult to find but as many as 3% of the population could be affected because age-related deficiency is relatively common in the over 65s and therefore on the increase in the UK due to the rising numbers of elderly people per capita.
To put these statistics in context, an all-boys school in the Home Counties of England with 1000 pupils would have approximately 80-85 color-deficient students. 11-13 would be deuteranopes, 11-13 would be protanopes, 11-13 would have a form of protanomaly and 62 would have a form of deuteranomaly.
About half of those with an anomalous condition would have a moderate to severe form of deficiency.
FAQ
Q: Can color blindness be tested in children?
A: Yes, color vision deficiency can be tested in children. Pediatricians, eye care professionals, and school screenings often include tests to identify color vision deficiencies in early childhood.
Q: Can color blindness affect an individual's safety?
A: In some situations, color blindness can impact safety. For example, individuals with a color vision deficiency may have difficulty interpreting color-coded warning signs or differentiating between certain colors in hazardous environments. However, alternative safety measures, such as using symbols or text alongside colors, can help mitigate these risks.
Q: Can corrective lenses, like glasses or contact lenses, help with color blindness?
A: No, corrective lenses like glasses or contact lenses cannot cure or correct color blindness. They only help improve visual acuity and focus but do not address the underlying color vision deficiency.
Q: Are there any famous individuals who are color blind? A: Yes, there are several famous individuals who have color blindness. Some notable examples include the painter Claude Monet and the scientist and inventor Thomas Edison.
Q: Can color blindness affects artistic abilities?
A: While color blindness may present challenges in perceiving and working with certain colors, it does not necessarily hinder artistic abilities. Many color-blind artists have developed unique techniques or styles that work around their color vision deficiency.