color vision deficiency facts and questions...
does a man/woman affected by CVD perceive this page?
Click on: Red/Green or Blue/Yellow color
filter (Be patient, the filter activation may take a minute
color do color vision deficient people dream in?
We only dream of what we know... People who become blind
after birth can see colors and images in their dreams. People
who are born blind do not see any images, but have dreams
equally vivid involving their other senses of sound, smell,
touch and emotion. It is hard for a seeing person to imagine
it. So, colorblind people dream in the color set they see
in real life... However, a full 12% of sighted people dream
exclusively in black and white!
a color deficient person experience 3D movies or stereoscopic
It depends on the color vision deficiency, and the degree
of severity. A color vision deficient person can see recent
3D movies which are devised to be seen with glasses using crossed
polaroid lenses, but not the old style 3D movies devised
to be seen wearing anaglyph (red-green) glasses. Redgreen
colorblind people do sometimes have difficulties with red-green anaglyph
images since although the colors appear similar,
the intensities are rather different - the red image typically
looks darker than the green.
do color vision deficient persons perceive a colorwheel?
over this standard colorwheel to see it as a colorblind
person might see it.
color blindness test
Color vision deficient people have a tendency to better night
vision and, in some situations, they can perceive variations
in luminosity that color-sighted people could not.
In fact, most color blind people can easily read what is
written in the picture below... That means, if you fail the
test, you probably have the full range of color sensitivity
that is attributed to color-sighted people. Anyway, this
test is not to be considered by itself sufficient to determinate
defective color vision.
(Highlight answer: NO)
taken from Sarcone's book Puzzillusions
bothers colorblind people most?
- When grilling a piece of meat, a red deficient individual
cannot tell whether it is raw or well done. Many cannot tell
the difference between green and ripe tomatoes or between
ketchup and chocolate syrup! Many others are always buying
and biting into unripe bananas - they cannot tell if they
are yellow or green, and the matt, natural material makes
it even harder to distinguish.
- Some food may look definitely disgusting to color vision
deficient individuals: a plate full of spinach, for instance,
just appears to them like cow pat.
- They can however distinguish some citrus fruits. Oranges
seem to be of a brighter yellow than that of lemons.
- A colorblind person is generally unable to interpret the
chemical testing kits for swimming pool water, test strips
for hard water, soil or water pH tests because they rely
on subtle color differences.
- Many colorblind people cannot tell whether a woman is wearing
lipstick or not. More difficult to handle for some is the
inability to make the difference between a blue-eyed blonde
and a green-eyed redhead.
- Color vision deficiencies bother affected children from
the earliest years. At school, coloring can become a difficulty
when one has to take the blue crayon - and not the pink one
- to color the ocean.
- Bi-color and tri-color LEDs (Light Emitting Diodes): is
that glowing indicator light red, yellow, or green? Same
problem with the traffic lights...
personal experiences of being a color blind
If you are a color blind person you may want to help us by
answering these two
need to pass a color blindness test for work. What can
Some jobs require their employees to take a color vision
deficiency test (often using the Ishihara plates above).
For instance, good color vision is vital for recognizing
various lights and signals important to pilots, especially
at night. These tests are required by, among others, the
coast-guard and most military and emergency services. Unfortunately,
if you really are colorblind, there is very little you can
do to pass these tests.
However, the CAA UK
and the FAA US
are currently reviewing the color vision requirements for
professional flight crew. Many documents and papers over
the last 20 years have stated the need for new color vision
tests that are more appropriate to the tasks that pilots
carry out. That is the reason why a new range of tests has
been developed by Applied
Vision Research Centre. For the few subjects
that fail or are judged borderline from the results of the
first CVD screening test, then a second program will measure
the subject's chromatic sensitivity for stimulus conditions
that are considered important experimentally. The results
from this will then make it possible to judge whether the
subject's performance meets the minimum color vision requirements
that yield acceptable visual performance in the tasks investigated.
No cure exists yet for inherited color deficiency. However,
Neitz and his wife have developed and used gene
therapy to restore color vision in two adult
male squirrel monkeys that have been unable to distinguish
between red and green hues since birth - raising the hope
of curing color blindness and other visual disorders in humans.
They introduced the human form of the red-detecting ‘opsin’ gene
into a viral vector, and injected the virus behind the retina
of the monkeys. The researchers then assessed the monkeys’ ability
to find colored patches of dots on a background of grey dots
by training them to touch colored patches on a screen with
their heads. After 20 weeks, the monkeys’ color skills
improved dramatically. The insertion of the red-detecting ‘opsin’ gene
gave rise to new color perception stimuli and, in fact, their
brain started to react on this new visual information. Gaining
this new dimension of color vision becomes a simple (!)
matter of splitting the preexisting "blue-yellow" pathway
into two systems, one for "blue-yellow" and a second
for "red-green" color vision.
The Neitz’s are still in the middle of clinical trials.
Actually, they are not only looking for a cure, but also
trying to develop a test that can help forecast the severity
of someone’s color blindness.
More info at http://www.neitzvision.com/content/genetherapy.html
can colorblind people compensate for their deficient
While there are no cures for color blindness, there are many
possibilities to help control the annoyance of this disease.
A possible treatment for color vision deficiency is to use special
glasses with red-orange filters to make it easier
to interpret colors or actually to better see contrasts.
Another way to control symptoms is to use what is called
the X-Chrom lens. The X-Chrom lenses are red contact
lenses worn on the non-dominant eye of color deficient
people and which helps some to better interpret colors or
contrasts. The X-Chrom lens does not restore normal color
vision, it just allows some colorblind individuals to distinguish
can I create a colorblind friendly website?
Apart from its aesthetic appeal, seeing many different colors
allows us to distinguish things in the world. However, remember
that there are always colorblind people among your audience
and readers. Actually, there could be more than TEN colorblind
people per 250 people visiting your site.
Then, we, the web community, must create an atmosphere which
makes it easier for colorblind individuals to differentiate
between text and background along with images! There are
2 ways that we can make information in pictures available
to colorblind people:
1) The simplest way is to increase the red/green contrast
in the images.
2) We can also convert the variations in red and green colors
into variations in brightness and/or blue/yellow coloration.
One way to test your website for colorblind usability is
by using these tools:
Web Page Filter,
Each tool will show a copy of your web page as if it was
seen as a select type of color vision deficiency.
Firefox also has a great add-on which allows webmasters to
see color contrasts:
Contrast Analyser Firefox Extension.
is a proposal of a color range selection that may be unambiguous
both to color vision deficient people and normal sighted
Some useful hints: when combining colors from this pallet,
try to use 'warm' and 'cool' colors alternatively. Avoid
combination of colors with low saturation or low brightness!
of colors unambiguous to color vision deficients
and to normal sighted persons
CMJN % 0,0,0,100.
CMJN % 15,41,93,1.
CMJN % 66,16,4,0.
CMJN % 81,15,62,2.
CMJN % 15,6,79,0.
CMJN % 90,49,12,1.
CMJN % 17,71,96,5.
CMJN % 26,62,12,0.
color vision deficients may see our corporate colors:
CMJN % 18,54,95,3.
CMJN % 81,15,62,2.
CVD resulting from insensitivity to red light, causing
confusion of greens, reds, and yellows.
Deuteranopia: CVD resulting from insensitivity
to green light, causing confusion of greens, reds, and
Tritanopia: a rare form of CVD resulting from
insensitivity to blue light, causing confusion of greens
can teachers help if a student has a color vision deficiency?
1) Always use white chalk, not colored chalk, on the board
to maximize contrast. Avoid yellow, orange, or light tan
chalk on green chalkboards.
2) Xerox parts of textbooks or any instructional materials
printed with colored ink. Black print on red or green paper
is not safe. It may appear as black on black to some color
vision deficient students.
am colorblind and work on a computer - is there a way
that I can determine the various colored graphics or
Yes, there is a new product called eyePilot that
might help you. It is an interactive software program that
takes a picture of your screen and allows you to manipulate
is the relation between colorectal cancer and color deficiency?
Men are statistically more likely to die of colorectal cancer
than women, and it is thought that one reason for this is
that they are more likely than women to be color vision deficient.
The link is that if you are red colorblind, when you look
at a piece of used toilet paper it may all look the same
color, even though there is red and brown on there. Hopefully,
the other symptoms will prompt the color deficient person
to seek medical attention (source: h2g2).
there 'false' colorblind persons?
There is a type of color vision deficiency that is caused
by damage to the cerebral cortex of the brain, rather than
abnormalities in the cells of the eye's retina. This kind
of color vision deficiency is called "cerebral
achromatopsia". People affected with cerebral
achromatopsia are perfectly aware of their visual experiences;
however, they are unable to imagine or remember colors. They
see the world like a black & white television where everything
is a shade of gray. They cannot chromatically order or discriminate
hue but they can distinguish color contrasts like a normal
person. 'Transient achromatopsia' is a temporary loss of
colour vision caused by a short-lived vascular insufficiency
in the occipital cortex.
cats and dogs color vision deficient?
Yes, we can compare man’s best friends’ vision
with the vision of human being suffering from red or green
color vision defiency (protanope, deuteranope, see fig. below).
Dogs do see in color, but have two-color, or dichromatic
vision, that is, they cannot distinguish between
red, orange, yellow or green. They can see various shades
of blue and can differentiate between closely related shades
of grey that are not distinguishable to people. Cats have
the ability to distinguish between blues and greens, but
lack the ability to pick out shades of red. However, cats
and dogs are primed to see "motion", rather than
defining the world through sight alone. They use a blend
of senses such as smell and hearing with their vision to
do what we humans use our eyes alone to do.
goldfish color vision deficient?
The common goldfish is not colorblind. It seems that it can
see a very wide range of the spectrum both infra-red and
ultra-violet and has the largest range so far discovered.
In that sense, it is tetrachromatic because
its color vision is based on four types of cones (ultraviolet,
short, medium and long wavelength-sensitive). Goldfish are
actually the only animals that can discriminate, under certain
conditions, both infra-red and ultra-violet light.
Since they have greater sensitivity to light than we do,
it is important then to protect your goldfish from bright
lights and sudden movements, and to spend a little time working
out the right location for their tank.
color test variant: the Farnsworth color arrangement
arrangement test", or more commonly – the
color arrangement test, was originally developed for Navy
use by Commander Dean Farnsworth in 1943 at the Naval Laboratory.
To take this color blindness test, simply grab and arrange
the colors in order, according to similarity, all along the
row. Once you are done, click the button to see your results,
then click again to see what type of color blindness you
may have. This version of the test was created
by Daniel Flück of Colblindor.com.
tools and resources used to test for color blindness
An "anomaloscope" is
an instrument that measures quantitative and qualitative
anomalies in color perception. You can take a color blindness
test with the help of a simple anomaloscope here.
If you know a new device for testing color blindness that
is not listed on our page, please, don't hesitate to share
it with our visitors/readers.