The eye is a complex piece of anatomy capable of determining everything from broad shapes to precise details. Among the many tasks the eye is able to perform, one of the eye’s key tasks is to aid in the determination of the many variations of color.
The brain is able to differentiate color based on the different wavelengths that hit and are transmitted by the retina. This is because the cones that, in part, make up the retina contain photo pigments sensitive to short, medium and long wavelengths of light often associated with the three primary colors red, blue and green. Absorption of combinations of wavelengths allow the brain to perceive the different variations of color (Stein, Stein, and Freeman, 2013, pg. 26). However, like with any other part of anatomy, problems can arise. Commonly, when the retina is unable to perceive certain colors it is referred to as color blindness. In truth, this title is misinformed since it is incredibly rare to only see in black and white. A better name for this condition is color deficiency since the issue is the result of a lack of one or more of the needed pigments (Stein, Stein, and Freeman, 2013, pg. 26). When certain pigments are missing, the retina cannot correctly read the wavelengths hitting the other pigments meaning the patient either views the color incorrectly or cannot see the color at all depending on the severity of the condition. This is why color deficiency would be a more appropriate term since patients are usually able to see some amount of color, even while having issues with others (Stein, Stein, and Freeman, 2013, pg. 26).
Additionally, the reasons in which a patient is color deficient are often misunderstood. Patients tend to think the root of color deficiency comes from an outside source such as medication or age. While it is possible for medication and age to change the pigments, this is largely not the case because the leading cause of color deficiency is actually a genetic mutation of the X chromosome (Waggoner, 2003). If a person is born with a deformed X chromosome, the photo pigments created from that chromosome are also deformed. Women are born with two X chromosomes so they would need to have a mutation on both chromosomes in order to be color deficient compared to men who only have one X chromosome. Since about 16% of women have the X chromosome defect, yet do not experience color deficiency, it is more likely that the condition affects men. A study done by Tikrik Medical Journal proved this fact by testing 150 patients against two different color deficiency tests. Of the 150 tested, 86.67% of the subjects were male (Ahmed and Dewachi, 2013, pg. 259). The gap between both genders is staggering since women would need issues with both X chromosomes to have a color perception skew. 1 in 12 men and 1 in 200 women are color deficient. It is important to understand the major cause of color deficiency and whom it primarily affects since color deficiency occurs prior to birth. This means a patient with an X chromosome problem has had to adapt to seeing color in a different way from everyone else for his or her entire life. By understanding both color deficiency and its source, steps can be taken to help those struggling in order to alleviate the largest obstacles that come with not seeing all colors and/or shades of color (Xin, Min, and Chuan, 2014, pg. 3).
Color Deficiency Types
Color vision goes well beyond whether or not the patient has a genetic imperfection. It is instead broken up into categories by type and extent. For instance, when the pigments in the retina are working correctly, a patient is trichromatic (Waggoner, 2003). Trichromats are able to see all colors and do not have color deficiency. A patient who is color deficient is one of three categories; protanomaly, deuteranomaly, or tritanomaly (Waggoner, 2003). Each of these types represent a different shift in wavelength sensitivity and can be mild, moderate or severe.
Let’s look at the types of color vision deficiency (CVD), in no particular order. Protanomaly, is a less common CVD. In this scenario, patients have trouble differentiating green and red. For example, a patient may leave the house wearing a green and red sock by accident (Albany-Ward and Sobande, 2015, pg. 197). Additionally, deuteranopia is the most common deficiency for a patient to have. Protanomaly is more severe since two of the three photo pigments are damaged. Those with protanopia have a hard time sorting out colors with similar wavelengths (Waggoner, 2003). Protanomaly is a bigger concern than deuteranomaly since the range of colors that can be confused is increased. The rarest form of color deficiency is tritanomaly, a condition where the patient has trouble distinguishing blue and yellow (Waggoner, 2003). Tritanomaly is less problematic than both protanomaly and deuteranomaly. It influences everyday life less than Protanomaly and Deuteranomaly since directions are based on the red and green spectrums rather than blue and yellow. Tritanomaly is also minor compared to deuteranomaly since it effects less people. Education on the different forms of color deficiency allow for greater chances to help those affected. When developments are made to support those with altered color visions, it is crucial to treat for all cases rather than only the most prominent forms and a proper understanding of each type will prevent any unintentional bias.
Over the years, there have been many variations of color vision tests. The reason for the many tests is because the tests are always evolving and improving. There have been eight major color deficiency tests; each unique in their design. The most famous test is the Pseudo-Isochromatic Color Plates Test (Ishihara) which consists of a series of colored plates each with a different color patterned number inside a pattern of other colored dots (Zhao and Subramanian, 2015, pg. 550). The patient views each plate and reads the number aloud. If the patient is successful, then he or she is not color deficient. Similar to the Ishihara Test, the Dvorine Pseudo-Isochromatic Plate Test also use a colored plates with numbers system, but add a color-naming test (Waggoner, 2003). While both these tests are popular, neither can test for tritanomaly, which can put patients at a disadvantage. The next color plate based test is the Standard Pseudoisochromatic Plates test. Unlike the last two plate based tests, the Standard Pseudoisochromatic Plates tests for protanomaly, deuteranomaly, and tritanomaly instead of only protanomaly and deuteranomaly (Waggoner, 2003). However, the disadvantage of the Standard Pseudoisochromatic Plates test is the test's inability to determine the severity of any of the issues it tests for which means the patient may have to take another test regardless (Waggoner, 2003).
The Wagner HRR and Color Test Made Easy are two tests specially designed for children by replacing the numbers inside the plates. These specific tests were created for children too young to understand the numbers used in the standard tests and replace them with either a shape in the Wagner HRR test, or a line that the child traces with his or her finger in the Color Test Made Easy (Waggoner, 2003). Each of the colored plate tests is designed so that either a number or image will appear in the colored dots on each plate. The tests are similar because the core method of testing is the simplest for a patient to understand regardless of age. A patient can sit down and predict what to do before the test begins due to the concept’s simplicity.
The last three do not use the numbered plates method. The Anomalscope, a test which has the patient compare a changing yellow light to a consistent red or green light, is not designed to test color deficiency, rather it was meant to verify previously taken tests (Waggoner, 2003). For cases where color deficiency is inconclusive, this test re-evaluates the subject to determine the severity of the condition and to re-affirm the judgment of the first test. However, this test is uncommon because it requires a patient to have taken a different color deficiency test prior. The Farnsworth D15 is a two minute test where the patient must match colored caps in order of closest proximity to a reference cap (Waggoner, 2003). Unlike the colored plate based tests, the Farnsworth D15 is not common due to time needed, number of parts and how easy it is for a patient to pass even with an issue. This test would later by replaced by the Ishihara Test for its ease in confirming color deficiency. The last test is the Farnsworth Lantern, a test used to sort out color deficient soldiers in the navy (Waggoner, 2003). Some jobs in the navy, like messaging ships, depend on color-based directions specifically in the red and green spectrum. The test specifically tests protanomaly by flashing either a red, green or white light eight feet away for two seconds. Any error that occurs results in the subject having to retake the test and only being allowed to get two tries wrong. Those who passed the second round are considered to have only minor protanomaly and are taught a series of directions not based on color. These variety of tests show constant improvement on how a color deficient patient should be established. The variation of tests make it possible for color deficiency to be observed in all who are affected regardless of age or condition (Waggoner, 2003). Interestingly, despite the various types of tests, one thing that connects every color deficiency test is the need for a specific light source since studies have shown that the light source used while testing can skew the results (Waggoner, 2003).
Color deficiency can affect a person’s life well beyond simply being unable to see specific colors. Driving is one example where a person’s color vision can negatively influence how well the person drives. Many elements of driving, such as signs and lights, are based in part around color. In cases where color deficiency is milder, patients depend on the order of lights, light brightness cues and sign shapes to guide them because traffic signals and signs are standardized (Stein, Stein, and Freeman, 2013, pg. 26). The standardized order of key road features is one of the biggest examples of help offered to those with color deficiency since it provides an alternative to a color based system. As a result, color deficient patients have the opportunity to drive where there previously was none. However, it is not uncommon for those with CVD to be tentative at traffic lights, slow for traffic signals unnecessarily and even go through red lights. Granted standardized landmarks can only help so much and those with decreased color vision still have problems while driving. A study done by Institute of Neurological Science shows that of the 151 color deficient subjects questioned, 126 admitted to having issues driving at night as well as stopping the car if the road lights change too quickly (Tagarelli et al., 2004, pg. 438). What is interesting about these results is that both cases are at times where color is not predictable. In the night result, the subjects are looking at colors that are dimmer than what they are used to seeing. Color is dependent on illumination. The second scenario describes the subjects’ difficulty to react when lights change suddenly. This is because the subjects are focused on the order rather than the color, so when the order is spontaneously switched, subjects need to re-evaluate the sequence. What this information reveals is that color deficiency can be more dangerous than what most people expect. Even with efforts to make driving more predictable, small changes can still cause major complications (Tagarelli et al., 2004, pg. 438).
Children with any form of color deficiency also have a huge disadvantage early on in life. Most teachers do not realize how prominent colors are in education. In fact, a poll done by researchers from the British Journal of School Nursing found that 26.3% of the surveyed teachers did not realize color affects a student’s ability to learn (Albany-Ward and Sobande, 2015, pg. 199). This is because teachers are unaware of why such an issue could hurt the child. The reason color deficient students struggle, especially early on, is because the student may be unable to understand material given in class. Examples can include worksheets, books, and supplies like crayons (Albany-Ward and Sobande, 2015, pg. 199). All these items are staples of a school environment, which is why they go, unnoticed. As a result, the child fears he or she is not as smart as the rest of the class and loses the motivation to want to learn. This is most apparent in earlier ages because color education has a higher relevance. In recent years in the UK, there has been a bigger push to help those with any form of color deficiency. Instances include labeling specific colored items and instructing teachers to look for warning signs of color deficiency (Albany-Ward and Sobande, 2015, pg. 199). While these adjustments may seem small, they are crucial in allowing a color deficient child to flourish since it gives the child access to the same resources as any other child (Albany-Ward and Sobande, 2015, pg. 199).
Color deficiency can cause complications even long after a patient has passed school. Color vision continues to impact a patient’s actions throughout his or her life. The study done by the Institute of Neurological Science also questioned subjects on their everyday lives and found color deficiency influenced both major decisions such as career paths to more minor issues such as a harder ability to recognize the colors of their favorite sports teams (Tagarelli et al., 2004, pg. 438). It is eye opening to see just how much of a difference color vision can make on a person’s life. The subjects recognized that color deficiency would limit certain capabilities, especially on the job market, and had to adapt to what each subject could do rather than what the subjects wanted to do. The confusion over the sports team colors is an example of color deficiency interfering with the subjects’ hobbies. Typically, color deficient people are thought to have trouble matching their own clothes, but the study shows that color deficiency affects both choices made and the subject’s ability to appreciate his or her pastimes. Other researchers discovered a link between what a person eats compared to that person’s color vision. The researchers found that the colors of certain foods alert the brain to what type of food is being eaten (Xin, Min, and Chuan, 2014, pg. 12). Since the colors of food impact what is being eaten, color deficiency may create an unbalanced diet depending on the colors a subject perceives. If cone sensitivity is shifted to the wrong wavelength (color), the brain may believe certain healthy foods are not beneficial. Knowledge of this will allow a color deficient person to be more aware of what he or she consumes in order to eat properly. Understanding the everyday life of a color deficient person can lead to great improvements in his or her life because it can help guide the person through obstacles he or she may not even realize affect him or her (Xin, Min, and Chuan, 2014, pg. 13).
Color deficiency education is so important because people often overlook how much the inability to see certain colors can change a person’s life. It affects everything from what jobs a color deficient person can do to small choices like what that person would want to eat. Since color deficiency does not physically hurt the patient, those without color deficiency do not realize the patient is being forced to adapt to a world in which he or she cannot properly perceive a significant portion. By educating people both with and without color deficiency of the effects of cone pigment problems, the gap between both perceptions can be significantly lessened.
Even today, efforts are still being made to improve the knowledge of color deficiency. In recent years, efforts have been made to make color deficiency tests more accessible to the public. One of the best methods of encouraging the public is through the use of online tests such as the Color Vision Plate Test found on EnChroma (Schmeder, McPherson, and Sheldon, n.d.). Trusted online tests like this one are important because it encourages patients to seek help by allowing the patient to understand the problem as well as provide assistance using the website. Continued research is the best way to help anyone affected with color deficiency regardless of severity because it widens the general public’s comprehension on the struggles a color deficient person faces and encourages new solutions to avert everyday troubles.
Ahmed, A. A., & Al-Dewachi, A. B. (2013). Comparison of two colour vision tests used in current ophthalmic practice. Tikrit Medical Journal, 19(2), 255-268.
Albany-Ward, K., & Sobande, M. (2015). What do you really know about colour blindness?. British Journal Of School Nursing, 10(4), 197-199 3p.
Schmeder, A., McPherson, D., Ph.D, & Sheldon, J. (Eds.). (n.d.). Test your color vision. Retrieved May 31, 2016, from http://enchroma.com/
Stein, H. A., Stein, R. M., & Freeman, M. I. (Eds.). (2013). The ophthalmic assistant: a text for allied and associated ophthalmic (Ninth ed.). Elsevier Saunders.
Tagarelli, A., Piro, A., Tagarelli, G., Lantieri, P. B., Risso, D., & Olivieri, R. L. (2004). Colour blindness in everyday life and car driving. Acta Ophthalmologica Scandinavica, 82(4), 436-442. doi:10.1111/j.1395-3907.2004.00283.x
Waggoner, T. L., Dr. (Director). (2003). How to Test for Colorblindness [Motion picture]. Home Vision Care Educational Material
Xin Bei V., C., Shi Min S., G., & Ngiap Chuan, T. (2014). Subjects with colour vision deficiency in the community: what do primary care physicians need to know?. Asia Pacific Family Medicine, 13(1), 1-20. doi:10.1186/s12930-014-0010-3
Zhao, J., Davé, S. B., Wang, J., & Subramanian, P. S. (2015). Clinical color vision testing and correlation with visual function. American Journal Of Ophthalmology, 160(3), 547-552.e1. doi:10.1016/j.ajo.2015.06.
Brianna Bischoff is a Raritan Valley Community College, Branchburg, New Jersey student in the Ophthalmic Science program. This research paper was written for a class taught by Dr. Brian Thomas, ABOM. At twenty years old, this is the first paper she has had published at the recommendation of her professor.