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Translational Studies for Inclusive Society
"Thinking about Color Perception Deficiency"

Writer: TOKUNAGA, Rumi (Chiba University)   terms: 2016 5


Distribution of rods and cones in relation to position on the retina of the left eye (Kankakuchikaku handobukku [Sense perception handbook] p. 924 Fig. 18.5.1) In our ordinary daily lives, we are not usually conscious of the act of seeing itself. The information obtained through vision, however, is very important to us. The visual perception we experience is the result of light from the outside world arriving at the retinas at the back of our eyes, and signals sent from these retinas being processed in our brains. The retina is composed of groups of different types of visual cells, and covers the inside of the eyeball. Light from the outside world is first absorbed by “rod” and “cone” cells. Figure 1 shows the distribution of these cells in the retina. The horizontal axis indicates angle of vision, with the point you are looking at being 0°, and the vertical axis indicates cell density. The density of cones is highest in the center of the visual field and decreases rapidly towards the periphery. Rods, on the other hand, are distributed more in the periphery than in the center. Cones function in bright places, and are involved in color perception. Rods have a higher sensitivity to light, and therefore function in dark places and allow us to see things at night. Color perception functions most at the center of the visual field, that is, around the spot where you are focusing your vision.

Understanding color vision deficiency

Color vision deficiency can occur congenitally when there is a problem with the pigment of the cone cells, and as an acquired condition caused by things like nerve or brain damage. The rate of congenital color vision deficiency in Japan is 5% for men and 0.2% for women.

According to the Ordinance for Enforcement of the School Health and Safety Act, testing of the color perception of school-aged children was removed as a mandatory element of health examinations in 2003. This can be seen as having been intended to protect children from things like bullying on the basis of color vision deficiency. But cases were reported in which children who graduate from school without knowing the characteristics of their own color vision face employment regulations involving color vision for the first time when they begin looking for a job. This led to a partial revision of the ordinance regarding color vision testing in April of 2014.

“①A system is to be created in which, in health consultations with school doctors, appropriate treatment can be provided as needed, including individual examinations and guidance with the prior consent of the school-aged child and their parent or guardian, ② School staff are to have accurate knowledge concerning color vision deficiencies, and the provision of appropriate guidance with consideration for color perception abnormalities in the context of academic guidance, student guidance, and career guidance is to be furthered. In particular, in order to prevent school-aged children suffering any disadvantage caused by not knowing the characteristics of their own color vision, there is a need to actively raise awareness among parties such as parents and guardians, [through actions] such as adding item concerning color vision to health surveys. (From the Ministry of Education, Culture, Sports, Science and Technology’s (announcement) “Concerning the partial revision of the Ordinance for Enforcement of the School Health and Safety Act, etc.”)

There are professions, such as pilot or sailor, that require determinations based on color information in situations in which lives are at risk, and in the past accidental collisions of trains and large ships caused by a misreading of signal colors have been reported. Surveys on the daily lives of people with color vision deficiencies have also shown that they have difficulties judging the freshness of foods and choosing the colors of things such as cars, walls, and makeup. According to a survey by Statistics Japan, in September of 2015 the male population of Japan was 60,900,000, and the number of men with color vision deficiencies was calculated to be 3,045,000. Twice the population of the city of Kyoto, the number of men with color vision deficiencies alone is far too large to be ignored.
Color vision tests: (a) Ishihara color vision test. (b) Panel D15 test

Figure 2 is a color vision testing tool. a) is an Ishihara color vision test, and b) is a Panel D15 test. These are simple color vision tests using the ability to see color, and they can reveal both the presence or absence and type of color vision deficiency. When you want to determine the type or degree of color vision in greater detail, there are other methods such as an examination with an anomaloscope by an ophthalmologist. The difference between individuals is great when it comes to color vision deficiencies, and in order to understand the characteristics of your own color vision it is necessary to know both the type and degree of your deficiency.

Support possibilities

We must raise awareness of the fact that the characteristics of a person’s color vision can give rise to a disability, understand the color world of people with color vision deficiencies, and think about how to best provide support as a society. In recent years, an approach called “universal design” has emerged in which objects are designed to meet the various needs of diverse users. In Japan this approach has expanded academically, with initiatives such as the issuance of practical guidelines for universal design by the Japan Ergonomics Society. These initiatives include “color universal design” that takes into consideration color perception. For example, the color scheme of publications issued by local governments to the general public have been arranged to intuitively communicate what information is important even to people with color vision deficiencies. Recently designers have begun to better understand the world seen by people with color vision deficiencies and implement this in their products, with even smartphone games, for example, being given settings to allow the color of game elements to be changed.

In places where education is provided, too, it is necessary to understand the characteristics of color vision and actively consider what sorts of measures can be taken to enable the communication of correct information to people with color vision deficiencies. Creating this kind of environment will make it easier to help parents and guardians understand the importance of color vision testing and encourage them to have their children tested, and allow people with color vision deficiencies themselves to correctly understand the characteristics of their own color vision and take measures on their own to prevent accidents and problems in their own lives. Our efforts to understand the world of color of people with color vision deficiencies will make it possible to provide them with information, and will lead to solutions for most of the problems that arise in the daily lives of people with color vision deficiencies.

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