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More color vision deficiency facts and questions...

How 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 or so...).

What 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!

Can a color deficient person experience 3D movies or stereoscopic images? 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.

How do color vision deficient persons perceive a colorwheel?

Reverse 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)

Image taken from Sarcone's book Puzzillusions

What 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... Your personal experiences of being a color blind If you are a color blind person you may want to help us by answering these two questions...

I need to pass a color blindness test for work. What can I do? 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.

Color blindness cure? No cure exists yet for inherited color deficiency. However, the researchers Jay 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 Neitzs 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 someones color blindness. More info at http://www.neitzvision.com/content/genetherapy.html

How can colorblind people compensate for their deficient color vision? 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 particular color 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 colors better.

How 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: - Colorblind Web Page Filter, - Vischeck. 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: - Color Contrast Analyser Firefox Extension.

Below is a proposal of a color range selection that may be unambiguous both to color vision deficient people and normal sighted persons. 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!

How 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.

I am colorblind and work on a computer - is there a way that I can determine the various colored graphics or letters? Yes, there is a new product called Visolve that might help you. It is an interactive software program that takes a picture of your screen and allows you to manipulate various color.

What 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).

Are 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.

Are cats and dogs color vision deficient? Yes, we can compare mans 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. They have a wider field of view about 200 degrees, compared with humans' 180-degree view. So, cats have a greater range of peripheral vision. They also are crepuscular, that means they are active at dawn and dusk. Their night vision is far superior to that of humans: cats' eyes have 6 to 8 times more rod cells, which are more sensitive to low light [Images: See What a Cat Sees].

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.

Are 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.

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Color Blindness Tests and Facts - Archimedes Laboratory

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