What Is Color Blindness?
Color blindness is the difficulty or inability to
distinguish colors caused by problems with the color-sensing pigments in the
eye. The majority of people who are colorblind cannot distinguish between red
and green. Distinguishing yellows and blues may also be problematic, although
this form of color blindness is less common.
The condition ranges from mild to severe. If you are
completely colorblind (achromatopsia), you
see only in gray or black and white. However, this condition is very rare. Most
people with color blindness see yellow, gray, beige, and blue in color charts
rather than the reds, greens, and teals that others see.
Color blindness is more common in men. Women are more likely
to carry the defective chromosome responsible for passing on color blindness,
but men are more likely to inherit the condition. According to the American
Optometric Association, nearly eight percent of white males are born with color
deficiency, in comparison to 0.5 percent of women (AOA).
Types of Color Blindness
There are three main types of color blindness. In the first,
the person has trouble telling the difference between red and green. In the
second, the person has difficulty telling yellow and blue apart. The third type
is called achromatopsia. A person with this form cannot perceive any
colors at all; everything appears gray. Achromatopsia is much more rare than
the first two types.
Inherited vs. Acquired Color Blindness
Color blindness can also be classified as either inherited
or acquired. Inherited color blindness is more common. It is caused by a
genetic defect. This means that the condition is passed on through
family—someone who has close family members who are colorblind is more likely
to have the condition as well.
Acquired color blindness develops later in life and can
affect men and women equally. Diseases that damage the optic
nerve or the retina of the eye
can cause acquired color blindness. For that reason, you should alert your
doctor if your color vision changes—it might indicate a more serious underlying
issue. Some of these underlying issues are discussed in the following section.
What Causes Color Blindness?
The eye contains nerve cells called cones that enable the retina, a
light-sensitive layer of tissue in the back of your eye, to see colors. Three
different kinds of cones absorb various wavelengths of light. Each cone reacts
to a different color, namely red, green, and blue, and sends information to the brain to distinguish colors. If one or more of these
cones in your retina has been damaged or is not present, you will have
difficulty seeing colors properly.
The majority of color vision deficiency is inherited, and is
typically passed from mother to son. Inherited color blindness does not cause
blindness or other vision loss. According to the National Institutes of Health,
the condition is very rare in women, but some degree of color blindness occurs
in 1 in 10 men (NIH, 2011).
You can also have the condition as a result of disease or
injury to your retina.
In glaucoma, the internal pressure of the eye (the
intraocular pressure) is too high. The pressure damages the optic nerve, which
carries signals from the eye to the brain
so that you can see. As a result, your ability to distinguish colors may be
diminished. According to the British
Journal of Ophthalmology, the inability of people with glaucoma to distinguish blue and yellow has
been noted since the 18th century (Pacheco-Cutillas & Edgar, 1999).
Macular degeneration and diabetic retinopathy cause
damage to the retina, which is where the cones are. This causes color blindness
and in some cases, blindness.
If you have a cataract, the lens of your eye gradually changes
from transparent to opaque. Your color vision may be dimmed as a result.
Other diseases that affect vision include diabetes, Parkinson’s, Alzheimer’s,
Certain medications can cause changes in color vision. These
include the antipsychotic medications chlorpromazine (Thorazine) and
The antibiotic ethambutol (Myambutol), which is used to
treat tuberculosis, may cause optic nerve problems and difficulty seeing some
Some heart and blood pressure medications, as well as
medications prescribed for nervous disorders, can put individuals at an
increased risk of developing acquired color blindness (Stresing, 2011).
According to the National Institutes of Health, the drug
hydroxychloroquine (Plaquenil) can also affect color vision (NIH, 2011). This drug is usually used to treat rheumatoid arthritis.
Color blindness may also be associated with other factors.
One factor is aging, in that vision loss and color deficiency can happen gradually
with age. Additionally, toxic chemicals, such as styrene (which is used to make
some plastics), have been linked to the loss of ability to see color.
Signs of Color Blindness
The most common symptom of color blindness is a change in
your vision. For example, it may be difficult to distinguish between the red
and green traffic light. Colors may seem less bright than before. Different
shades of a color may all look the same.
Color blindness is usually detected at a young age when
children are learning their colors. In some people, the problem goes undetected
because they have learned to associate specific colors with certain objects.
For example, they know that grass is green, so they call the color they see
green. If symptoms are very mild, a person may not realize that they are not
seeing certain colors.
If you suspect color blindness in either yourself or your
child, you should consult a doctor. A physician will be able to confirm the
diagnosis and rule out other, more serious, health issues.
Testing for Color Blindness
Seeing colors is subjective. It is impossible to know
whether you see reds, greens, and other colors exactly the same way as people
with perfect vision. However, your eye doctor can test for the condition during
a normal eye exam.
Testing will include the use of special images called pseudoisochromatic
plates. These images are made up of small, colored dots that have numbers or
symbols embedded within them that can only be seen by people with normal
vision. If you are color blind, you may not see the number or may see a
different number. It is important to have children tested before they start
school, because many early childhood educational materials involve identifying
Coping With Color Blindness
If color blindness occurs as the result of illness or
injury, treating the underlying cause may help to improve color detection.
However, there is no cure for inherited color blindness.
Your eye doctor may prescribe tinted glasses or contact lenses that can assist
in distinguishing colors.
People who are colorblind often consciously apply certain
techniques or use specific tools to make life easier. For example, memorizing
the order of the lights from top to bottom on a traffic light removes the need
to distinguish its colors. Labeling clothing can assist in matching colors
properly. Some software applications transform computer colors into those that
colorblind people can see.
If you have inherited color blindness, it is a lifelong
challenge. While it may limit prospects for certain jobs (for example working
as an electrician who must tell the difference between color-coded wires) most
people find ways to adjust to the condition.