Color blindness FAQ - ITKnights

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Color blindness FAQ

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What is color blindness?
Color blindness, or Color Vision Deficiency (CVD), a color vision deficiency, is the inability to perceive differences between some of the colors that others can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve, or brain damage, or due to exposure to certain chemicals.
The normal human retina contains two kinds of light cells: the rod cells (active in low light) and the cone cells (active in normal daylight). Normally, there are three kinds of cones, each containing a different pigment. The cones are activated when the pigments absorb light. The absorption spectra of the cones differ; one is maximally sensitive to short wavelengths, one to medium wavelengths, and the third to long wavelengths (their peak sensitivities are in the blue, yellowish-green, and yellow regions of the spectrum, respectively). The absorption spectra of all three systems cover much of the visible spectrum, so it is not entirely accurate to refer to them as "blue", "green" and "red" receptors, especially because the "red" receptor actually has its peak sensitivity in the yellow. The sensitivity of normal color vision actually depends on the overlap between the absorption spectra of the three systems: different colors are recognized when the different types of cone are stimulated to different extents. Red light, for example, stimulates the long wavelength cones much more than either of the others, and reducing wavelength causes the other two cone systems to be increasingly stimulated, causing a gradual change in hue. Many of the genes involved in color vision are on the X chromosome, making color blindness more common in males than in females
What is color blindness test?
The most commonly used test to detect color vision deficiencies was developed by the Japanese ophthalmologist Shinobu Ishihara (1879-1963). While working at the Military Medical School he was asked to devise a test to screen military recruits for abnormalities of color vision. His assistant was a colorblind physician who helped him test the plates. A collection of 38 plates filled with colored dots build the base of this test. The dots are colored in different shades and a number is hidden inside with shades of another color.
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....
I need to test a color blindness for work, what can I do?
Some jobs require their employees to take a color vision deficiency test (often using the Ishihara plates). 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. To test color blindness, simply use our Color Blindness Test Plates.
Is there any cure for color blindness?
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 lens is a red contact lens 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.
I am colorblind and work on a computer - is there a way that I can determine the various colored graphics, letters, …?
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 various color.
What is the meaning of downloadable version of color blindness test plates?
It means that you can download the whole 38 color blindness test plates to your computer in "jpg" format, and view, or print them in color.  (contact us for details)
Is the digital copy of the color blindness test plates is different in color than the printed one?
No, they are the same.
What are the benefits of the downloadable color blindness test plates?
  • Perform color blindness test on your computer for your patients or yourself.
  • Print the color blindness test plates on any paper type and at any time you want.
  • Buy the whole Color Blindness Test Plates at low price.
  • Copy the color blindness test plates to your mobile phone or your laptop and take them where ever you go.
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