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A Nurse’s Guide to Color Blindness Assessment


When most people are asked to identify colors, the answers given are generally similar. However, some people have a color vision deficiency that causes them to see colors differently. In some cases, these deficiencies are extreme, a situation more commonly known as color blindness. Color blindness is most often found to be genetically inherited due to abnormal photopigments. These photopigment defects create three types of color blindness. Most commonly found is a red-green color blindness, with blue-yellow color blindness being a close second. Not being able to see any color, or total color blindness, is very rare. Occasionally, someone can become color-blind from physical or chemical damage, and age can sometimes impact the way people see colors.

Signs and Symptoms

Because color blindness is most commonly genetically inherited, signs and symptoms show up early in one’s life. Children born with this disability have difficulty identifying colors correctly. Signs to look for in children include regularly identifying colors incorrectly, trouble recognizing red or green items, lack of interest in coloring, sensitivity to light, and difficulty reading color-based books. Adults who have acquired a loss of color vision are often harder to diagnose due to denial of health issues associated with getting older. However, there are conditions such as glaucoma, diabetes, and macular degeneration that carry a higher risk of color blindness, so it’s important to note any change in color vision as a possible symptom of a more serious problem.


Types of Color Blindness

There are many types of color blindness, which fall into three major categories: trichromacy, dichromacy, or monochromacy. When all three types of a person’s cone cells work but one is slightly off, this is called trichromacy. Trichromacy creates a wide range of how colors are viewed. Those diagnosed with dichromacy have only two functioning cone cell types, which creates an inability to see greens, reds, and sometimes blues. Monochromacy is the rarest of color blindness types and causes a person to only see in black and white.



Color blindness is often inherited. This disability is a result of the retina, found in the back of the eye, not functioning correctly. The retina contains three types of cones, cells that allow you to see color, and these cones respond to colors; one responds to red, one to green, and one to blue. When one or more of these types of cones doesn’t function properly, it changes the way colors are seen. Although many people, mostly men, are born with this defect, injuries or medical conditions can damage the retina cones later in life, causing a loss of color vision.



Color blindness is usually diagnosed by an optometrist by using a series of simple screening tests. Tools such as the Ishihara and Hardy-Rand-Rittler tests are used to determine the severity of the color deficiency. During these tests, the patient identifies numbers and letters in images made up of colored dots. The optometrist then uses this information to diagnose a color deficiency.



Living with color blindness makes everyday tasks difficult. Many parts of life, from education to cooking or even driving, involve the need to recognize different colors. Luckily, there are ways to help those with color blindness overcome these obstacles. Early diagnosis is key to helping a child adjust and learn to manage their color deficiencies. Parents and teachers can avoid using color-coding in learning exercises. Parents can purchase clothing that matches no matter which items the child picks out to wear. For older children or adults who have late-onset color blindness, there are computer programs and other technologies, such as special glasses, that work well to help those who have difficulty with colors. Additionally, some cell phones now have a function that allows users to adjust the colors based on their specific color blindness.


Ishihara Color Test

The Ishihara test is a color blindness test that was created in 1917 by Dr. Shinobu Ishihara, a professor at the University of Tokyo. The test consists of a series of plates, each containing a circle created out of random-sized and colored dots. Within the circle, a pattern of dots forms a number. Some of the number patterns are designed to be difficult for those with different types of vision deficiencies. Although this test is more than 100 years old, it is still a good test for color blindness, and thus, it is still used today.


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