Color vision Q&A


Color vision tests in schools are conducted the same as visual acuity tests. Some people think that children who make mistakes in reading the test plates cannot later obtain a driving license, go into the sciences, or become a teacher because of “color vision deficiency,” “color blindness,” or “weak color vision.”

The truth is, however, that even children with color vision deficiency can obtain a driving license or become a doctor, pharmacist or teacher.

In 1995 the School Health Act was partially amended so that schools did not test for hereditary color vision ability, but rather to find out which children may experience disadvantages in school because of their color vision and to take appropriate follow-up measures as necessary.

My wish is to help people acquire a proper awareness of color vision so that they can provide instruction that allows children to take advantage of their natural traits and enjoy their time in school.

Q1 Is color vision deficiency an inborn trait?
A1 The color vision deficiency that schools have traditionally dealt with is inborn (congenital). However, congenital color vision deficiency is something that should be diagnosed by a doctor.

Comment 1

The condition generally referred to as color blindness is congenital. This is something that a doctor diagnoses using a variety of test instruments. In addition to congenital color blindness, color sense may change because of disease after birth. This is called acquired color blindness. Such conditions resulting from disease include decrease or loss of function of the retina (the innermost layer of the eyeball) or other nerves, but these conditions are very rare.

Q2 What are the types of congenital color blindness?
A2 There are three types of color blindness based on ophthalmological diagnosis (protanopia, deuteranopia, and tritanopia), but they are not major characteristics of a person in daily life.

Comment 2

Human color sense is formed by the action of sensing three colors: red, green and blue. Academically, it is classified as follows depending on which of the three has decreased function.

• Protanopia: Decreased sensitivity to red
• Deuteranopia: Decreased sensitivity to green
• Tritanopia: Decreased sensitivity to blue
Of these three, deuteranopia is the most common. Protanopia is less common and tritanopia is very rare. No sweeping judgments can be made about how a given color will be seen in each case, but there is some regularity in which color combinations are difficult to distinguish. This characteristic is used in the Color Mate Test (CMT; a color test used for school education that is described below).

What is the prevalence of color vision deficiency??
A3 The prevalence is color vision deficiency is often said to be 2%, but that is for men and women combined. However, there are large differences between males and females. The prevalence in males is about 4.5% and that in females is about 0.2%, a 20-fold difference.

Comment 3

The prevalence of color vision deficiency in Japan is reported in the media to be about 4.5% in males and 0.2% in females. There are large differences between males and females regarding the heredity of color vision deficiency. The difference is about 20-fold. However, about one in ten women carries the gene for color vision deficiency. This is discussed in greater detail below.

Is color vision deficiency hereditary??
A4 Color vision deficiency typically shows sex-linked recessive inheritance, and unlike dominant traits is not expressed unless two factors are present. Thus, it is passed from mother to child.

Comment 4

As mentioned in Q3 above, color vision deficiency is seen in 4.5% of males and 0.2% of females in Japan. It follows a semi-recessive inheritance pattern that has a fixed relationship with gender in which the mother plays a major role. One in ten women has the genetic factor for color vision deficiency (i.e., is a “carrier”), but these women have normal color vision.

The heredity of color vision deficiency is due to genes on the X chromosome, which determines sex. Females have two X chromosomes and males have one. Of course there are many genes other than those for color vision on the X chromosome. Since the inheritance pattern for color vision is sex-linked recessive, even if a women has one abnormal gene on an X chromosome the trait is not expressed as abnormal, and color vision is normal. However, the gene is present. These women are called carriers, and may pass on the gene for color defective vision to their children.

The percentage of females with color vision deficiency is 0.2%, or 2 in 1,000, but one in 10 women are carriers. For women, this is not a problem of others; it is the major reason why color vision deficiency is often blamed on the mother. In contrast, men have one X chromosome and if that chromosome has the gene for color vision deficiency the individual will have color vision deficiency.

Informed consent is required for genetic testing. The person to be tested must receive a full explanation of what the test is for, and give his or her consent to be tested. Follow-up measures are even more important and strict caution is needed to prevent leaks of information. In the light of this, careful thought needs to be given to performing color vision tests.

Q5 The term “color special vision” is heard recently. How does this differ from color vision deficiency?
A5 Conventionally, people who made mistakes in reading the test plates of the Ishihara color test were said to have color deficient vision. However, with the amendments to the School Health Act enforcement regulations in 1995, some people called for the term “color special vision” to be used in cases when consideration of colors was needed in school education.

Comment 5

It used to be that innate (congenital) color vision deficiency was investigated based on the School Health Act, but since 1995 the aim has been not to look for congenital color vision deficiency but to understand whether or not a child requires special consideration in school education and to take appropriate measures if so.

Even among children who make mistakes in reading the school version of the Ishihara color test, not that many will need special consideration for learning in school. There are some, however, who will have difficulty distinguishing color combinations commonly used in schools, especially browns and greens, pinks and blues, and purples and blues. That is referred to as “color special vision.”

To test for such difficult-to-differentiate colors, the CMT school color vision test may be used.

Q6 How does a person with color special vision see colors?
A6 Precisely how colors are seen by people with color vision deficiency is not understood by current science and medicine. The CMT will tell us which color combinations from among the 100 or so colors used in schools are likely to be difficult for children with color special vision to tell apart.

Comment 6

-This is generally referred to as color deficient vision, or with the terms color blindness and weak color vision.

Taken literally, the term “color blindness” can lead to the mistaken impression that it means “blind to colors,” or “inability to see colors.” The term “weak color vision” may be taken to mean weak color sensation, from which there would be a tendency to think that it is milder than color blindness, but both of these are mistaken impressions from taking the meaning of the terms too literally.

Color blindness/weakness is diagnosed with a precision instrument called an anomaloscope, but even this instrument cannot judge the severity. Color vision deficiency is complex. It is unfortunate that terms such as color blindness and weak color vision have become so widespread.

To combat these misperceptions, the terms color vision deficiency or color blindness are used in school health in the city of Nagoya. The term weak color vision is not used, and we are trying to make people more familiar with the term “color special vision” so that it is used more widely.

Q7 What is the purpose of the color vision test in school?
The color vision test used in school should be used to help teachers and others understand whether a child will experience any difficulty in school. It is not performed to find out which children have color vision deficiency.

Comment 7

At the time of the amendments to the School Health Act enforcement regulations in 1995, the Japanese Society of School Health prepared a manual called the “Schoolchildren Health Check Manual.”

This manual states that “health checks performed in school, unlike medical examinations performed in hospitals and medical clinics or examinations performed for the diagnosis of disease, are tests done so that problem areas do not cause anxiety in children or their parents.” It also says that, “Fundamentally, the purpose is to find out whether a child will face any obstacles to learning because of his or her color sense, or will need special consideration with regard to colors in learning, not simply to detect color vision abnormalities.”

In other words, the tests are done so that teachers and others can be aware of potential problems and take measures to avoid learning obstacles in children with color vision deficiency, not to search for color blindness as a disease.

Q8 What kind of difficulties do children with color special vision face in school?
A8 Students determined to have color special vision will differ individually in how they see color combinations, and careful attention is needed to deal with this

Comment 8

Even among the people around these children, many will find out that the child has color vision dificiency for the first time in the school color vision test. This is particularly true in tests with the traditional Ishihara test plates (circles containing dots of different colors so that a number or figure is hidden) that are generally used. It may be that this is what congenital abnormalities are like, but in fact until the test many people with abnormal color vision live their lives without either themselves or those around them noticing anything special.

Some teachers and ophthalmologists think that it is better to make the child aware of his impairment as early as possible so that he can prepare for his or her life in the future. In the field of public health, however, identifying impairments for which there is no treatment is sometimes looked down on as doing nothing more than causing distress to the affected person. In society as well, rather than deliberately singling out a condition that causes an individual little inconvenience in daily life, a better approach would seem to be to create an environment in which that individual can feel secure in life while accepting that he or she has this impairment.

A world declaration by UNESCO also states that genetic diseases should not be taken up lightly, and with an emphasis on social thinking in school health the declaration states that an impairment which does not interfere with school life is not considered to be an impairment.

Q9 How are color vision tests conducted in schools in Nagoya?
A9 After the School Health Act was revised in 1995, only fourth grade elementary school children had to take a color vision test. In Nagoya, screening was done with the Ishihara test and afterwards the CMT was used for appropriate follow-up measures. In the future we would like to put more emphasis on the CMT.

Comment 9

1) Testing with the CMT
The CMT currently used in Nagoya is not a test to determine whether or not a child has a color vision abnormality. It is used to understand which color combinations each child with color special vision may have difficulty telling apart and to show what kind of care should be taken in daily life.

People with color special vision have a general understanding of the color combinations that are difficult for them, but there is nothing that shows this with colors that are actually used.

The CMT uses colors that are used in current textbooks in test plates that help us to understand which color combinations a child has difficulty differentiating. An important thing is that it is a test with colors that are actually used. This helps those around a child with color special vision to become more aware of color use.

2) Follow-up measures
After identifying the color combinations on the CMT that are difficult for a child, copies of those colors are given to the child’s teacher and parents. Meetings to explain color vision are held with these children and their parents to improve their knowledge about color vision.

Q10 How should the Ishihara test be used?
A10  The Ishihara test that is generally used gives results that are equivalent to a genetic test, and so should not be used by school nurses in schools. It should be used by school doctors. The Ishihara test is very sensitive, and there is a risk that children whose color vision causes them no difficulty in learning will be considered disabled. We do not believe that it complies with the Ministry of Education’s policy to use tests “that do not cause anxiety,” and suggest that it be used as an auxiliary test.

Comment 10

Today the Ishihara test is still the most commonly used color vision test in both schools and the workplace. It is a medical test that is considered the global standard. In Japan there are other outstanding tests, but none of them can be used to investigate the level of disadvantage people will have in regular daily life in society. In real life color is not as simple as the theoretical color combinations used in the Ishihara test. In addition, there are complex relationships with various factors other than color.

Color vision test plates that can tell us an individual’s vocational aptitude do not exist in the world today. The results of such tests alone also do not tell us whether or not a child will suffer disadvantage in school.

The Ishihara test is also problematic for girls in that it frequently identifies girls with normal color vision as impaired (that is, it has a high false positive rate for girls). For children in the lower grades of elementary school who clearly perceive colors incorrectly, guidance needs to be given with their special color sense in mind.

Q11 What happens to people with color special vision in advanced education and employment?
A11  They can advance to high school and university with almost no problem. Restrictions in employment are becoming fewer, and there are a growing number of fields in which they can find employment.

Comment 11

In the past there were restrictions in getting into university science departments, but today only two or three universities, including the National Defense Academy and merchant marine universities do not allow people diagnosed with color blindness to take their entrance examinations. In the past there were not only employment restrictions in science-related fields but also, for a time, even in liberal arts fields. Today, however, restrictions are steadily being removed for medical professionals, including doctors and pharmacists, teachers and general occupations.

Driver’s licenses can also be obtained if a person can correctly recognize the color of traffic lights. The efforts of many people have led to an expansion of the fields of employment as long as the individual can perform the actual work without hindrance.

People with color special vision may have problems in some cases finding work or obtaining qualifications in the future, but these young people should be given guidance so that they acquire widespread interests and abilities without deciding beforehand what they will be able to do.

Q12 What can we do to make a society in which it is easy for people with color special vision to live?
A12 Color special vision is not a disability, and so we need to stop using words like “abnormal” or “defective” and create a better environment. We should respect the fact that each of us has our own color vision world.

Comment 12

The misunderstanding that color blindness means not being able to see colors has spread, and there are still people who think that people with color vision deficiency are disabled.

Some people with color vision deficiency have color discrimination ability that is somewhat weak in certain areas, but most have no special problems in daily life. Therefore, words such as disability or impairment are not appropriate, and also give rise to misunderstandings.

In school health in Nagoya, we have decided to call this color special vision. However, “special” also has the meaning of some exceptional ability, and so we are currently trying to think of a better term.

Society is becoming more considerate of people with vision impairments. One example of this is the braille blocks that are used in sidewalks. Unlike a generation ago, color use in school textbooks is also changing so that colors are easier for people with color special vision. We hope that traffic lights also will not depend on color only but also incorporate shapes as is done in some other countries. An environment needs to be created so that all people can go about their lives without discomfort or anxiety.

Q13 How should teachers deal with children who have color special vision?
A13 First, they should acquire a proper understanding of color special vision. That will make it easier for children under their care, and these accumulated experiences will make for a brighter society and future.

Comment 13

It is well-known that the famous painter Vincent van Gogh had color deficient vision. There is also a case in which many of the best paintings in an art exhibit in one city were done by children with color special vision. However, there are also children who use color that would never be considered by people with normal color vision. In such cases, there is no reason to correct them as long as one recognizes this as an individual characteristic of color special vision. Teaching young children is difficult, but kind consideration based on this kind of broad knowledge will help to bring out the best in them.

Not many countries hide color special vision as much as Japan. Aside from cases in which the children themselves feel they have special characteristics, when children with no special problems are told by those around them that they have an impairment and treated as disabled, it is deeply hurtful to them.