Color blindness, also known as color vision deficiency, is the decreased ability to see color or differences between colors. It most often affects males rather than females for genetic reasons.
Overview of Color Blindness
Color blindness arises from abnormalities in the development of certain cells in the retina that are sensitive to color. These cells are called cone cells, and there are three types that detect different wavelengths of light that we interpret as red, green, and blue light.
When one or more of these cone cell types is absent or not functioning properly, color vision is impaired. The most common type of color blindness makes it hard to distinguish between red and green. Other types make it difficult to tell the difference between blues and yellows, or reds and oranges.
Complete color blindness, where an individual can only see in black and white, is very rare. Most color blind people have a type of red-green color blindness and are able to see some color, just not as vividly or distinctly as others.
Prevalence in Males vs. Females
Color blindness affects a much higher percentage of males than females. According to the National Eye Institute, about 8% of men and 0.5% of women with Northern European ancestry have the common red-green color vision deficiency.
For other populations, estimates are:
- 1% of African-American males
- 5% of Asian males
- 4% of Hispanic males
- Less than 1% of females of any race
So in summary, about 1 in 12 men (8%) and 1 in 200 women (0.5%) with Northern European ancestry have a red-green color vision deficiency. For other populations, the percentage of affected males ranges from 1-5%, while females remain under 1%.
Genetic Cause
The reason color blindness affects males much more frequently than females is because the genes for the color vision receptor cells are on the X chromosome. Females have two X chromosomes, while males have one X and one Y chromosome.
A defect in the gene for one of the color receptors on a single X chromosome will cause color blindness in males, because they have no second X chromosome with a normal copy of the gene. For a female to be color blind, she must inherit defective color vision genes on both of her X chromosomes, which is much less likely.
Types of Color Blindness
There are several different types of color blindness depending on which color receptors are affected:
- Red-green color blindness – not distinguishing red and green; most common type
- Blue-yellow color blindness – confusion between blue and green, and also yellows
- Complete color blindness – seeing only in shades of grey, very rare
Red-green color deficiency makes up about 99% of cases of color blindness. Within this type, there are different levels of severity:
- Protanopia – complete absence of red retinal receptors
- Deuteranopia – complete absence of green retinal receptors
- Tritanopia – complete absence of blue retinal receptors
- Protanomaly, deuteranomaly, tritanomaly – partial absence of red, green, or blue receptors respectively
Those with a complete absence have more difficulty distinguishing colors than those with only a partial loss of one type of color receptor.
Impacts of Color Blindness
The inability to see colors properly can make some tasks more challenging, but it is typically not severely disabling. The impacts are usually relatively minor and those affected learn to adapt. Some potential difficulties include:
- Trouble recognizing red/green/brown colors of traffic lights or signal wires
- Difficulty reading colored graphs and charts
- Inability to see a red ball against green grass
- Less able to appreciate the vividness of sunsets, fall foliage, and other colorful scenes in nature
- Challenges in professions that rely heavily on color discrimination such as electricians, pilots, artists, graphic designers, etc.
With appropriate adjustments, accommodations, and awareness, the impacts of color blindness can be minimized. Many affected individuals adapt well and lead perfectly normal lives.
Diagnosis of Color Blindness
Color blindness can be detected using several different screening tests. These tests display a series of dots or shapes in colors that are difficult for color blind individuals to distinguish:
- Ishihara test – contains circle of colored dots appearing as a number or shape to normal vision, invisible to color blind
- Farnsworth D-15 test – arrange colored caps in order of hue
- Lanthony desaturated D-15 test – arrange more subtly different colored caps
- Hardy-Rand-Ritter (HRR) test – identify colored dots
These screening tests can identify possible color vision deficiencies. More precise diagnosis of the type and severity can be determined using alternative tests under different lighting conditions.
Early diagnosis is optimal, preferably during childhood vision screening exams. However, color blindness can be detected at any age if it has not been picked up before.
Treatment for Color Blindness
Currently there is no cure for color blindness. The retinal color receptor cells that are absent or malfunctioning cannot be repaired. However, some adaptive assistive options may help those affected manage their color vision deficiency.
- Tinted eyeglasses or contact lenses – filter out wavelengths to increase color contrast
- Electronic aids – color identifiers using LED lights attaches to clothing or items
- Mobile apps – allow capturing an image and adjusting colors to differentiate hues
- Occupational aids – tools tailored for specific tasks impacted by color confusion, such as labeling wires
People with color blindness can also modify their environment to help distinguish colors more easily. Using certain color combinations that create higher contrast allows color blind individuals to discern them more reliably. With some adjustments, those with color vision deficiencies can manage well.
Conclusion
In summary, color blindness or color vision deficiency is an inherited condition that primarily affects males. About 8% of males and 0.5% of females with Northern European ancestry have some type of red-green color blindness. For other populations, the rates are 1-5% in men and under 1% in women.
The genetic cause of color blindness is defects in the genes encoding for color-sensing retinal cone cells. These genes are located on the X chromosome of which males have only one, while females have two. So males only need one defective gene to cause color blindness while females require both copies to be abnormal.
While color blindness can create some challenges in daily life, most of the effects are relatively minor inconveniences. With some adaptive strategies and aids, people with color vision deficiencies can manage well and lead perfectly normal lives and careers.
