Know More About color blindness & Color Blindness Factsheet (for Schools)

• colour blindness, inability to distinguish one or more of the three colors red, green, and blue. Most people with color vision problems have a weak color-sensing system rather than a frank loss of color sensation. 
• In the retina (the light-sensitive layer of tissue that lines the back and sides of the eyeball), humans have three types of cones (the visual cells that function in the perception of color). One type absorbs light best in wavelengths of blue-violet and another in the wavelengths of green. 
• The third type is most sensitive to longer wavelengths—more sensitive to red. Normal color vision, when all three cone types are functioning correctly, is known as trichromacy (or trichromatism).

Types of color blindness

• There are several different types of color blindness, which may be subdivided generally into dichromacy (dichromatism), when only two cone types are functional, and monochromacy (monochromatism), when none or only one type of cone receptor is functional. 
• Dichromatic individuals are ordinarily unable to distinguish between red and green. 
• Blindness to red is known as protanopia, a state in which the red cones are absent, leaving only the cones that absorb blue and green light.
•  Blindness to green is known as deuteranopia, wherein green cones are lacking and blue and red cones are functional. 
• Some persons experience anomalous dichromatic conditions, which involve only minor reductions or weaknesses in color sensitivity. In protanomaly, for example, sensitivity to red is reduced as a result of abnormalities in the red cone photopigment. 
• In deuteranomaly, in which sensitivity to green is reduced, the green cones are functionally limited. Two forms of blue-yellow color blindness are known: tritanopia (blindness to blue, usually with the inability to distinguish between blue and yellow), which occurs when blue cones are absent; and tritanomaly (reduced sensitivity to blue), which arises from the abnormal function of blue cones.
• Monochromacy, or complete color blindness, is sometimes accompanied by deficiencies in visual acuity. 
• Such conditions are rare and include achromatopsia (or rod monochromacy; the complete absence of functional cone photopigments) and cone monochromacy (when two of the three cone types are nonfunctional).

Inherited and acquired color blindness

• Hereditary red-green color blindness occurs mainly in males and Caucasian persons, with about 8 percent of men and 0.5 percent of women of European ancestry inheriting the conditions.
•  Its predominance in males is due to the fact that red-green color blindness is a sex-linked recessive characteristic, carried on the X chromosome. 
• Hence, the test for red-green color blindness is passed from mother to son, from mother to daughter, or from mother and father to daughter.
• A son who inherits the trait from a carrier mother will be red-green color blind (males inherit only one X chromosome, directly from the mother).
•  A daughter who inherits the trait from a carrier mother (with a normal father) will have normal color vision but be a carrier of the trait. A daughter who inherits the trait from both her mother and her father will be red-green color blind.
• Blue-yellow color blindness, by contrast, is an autosomal dominant disorder and therefore is not sex-linked and requires only one copy of the defective gene from either parent to be expressed. 
• Achromatopsia is an autosomal recessive disorder, occurring only when two copies of the defective gene (one from each parent) have been inherited. 
• Persons who inherit color blindness may show symptoms at birth (congenital color blindness), or they may become symptomatic later, in childhood or adulthood.

Acquired color blindness is usually of the blue-yellow type and ranges from mild to severe.

• Often it is associated with chronic disease, such as macular degeneration, glaucoma, diabetes mellitus, retinitis pigmentosa, or Alzheimer disease. Certain drugs and chemicals can also cause acquired color blindness.

What Teachers Should Know

• Color blindness is caused by problems in the color-detecting nerve cells located in the back of the eye, called cones. 
• As a result, some people have trouble telling the difference between red and green (the most common kind of color blindness), and between blue and yellow. 
• Achromatopsia is a rare a form of color blindness in which people can't see any colors — they only see shades of gray.
• Parents or teachers may suspect color blindness if a child seems to have trouble seeing certain colors. Kids and teens who are color blind have normal vision — they just don't see certain colors the way others do., A simple Colorblind test can help <aherf=" https://www.colorblindtest.co /"> identify color blindness </a>

Many people with color blindness don’t even know it. People who are color blind see normally in other ways and can do normal things, such as drive.

• They just learn to respond to the way traffic signals light up, knowing that the red light is generally on top and green is on the bottom. 
• Some people can use special contact lenses and glasses to help them see some color differences, but there is no cure for color blindness.

Students who are color blind may

• Not be able to tell the difference between certain colors or shades of similar colors
• Have trouble with assignments or projects that require them to use color
• Need more light in the classroom and seating accommodations
• Feel self-conscious or frustrated about not being able to see colors
• Be teased or bullied because of color blindness

What Teachers Can Do

• Getting to know and understand what color blind students can and cannot see — from parents or guardians, other teachers, and the student themselves — will help you understand and meet their needs much better. 
• Color blind students may be eligible for a 504 plan, which can provide extra support.

Ways to help a student with color blindness include:

1. writing in black on a <a href="https://www.microsoft.com/en-in/microsoft-365/microsoft-whiteboard/digital-whiteboard-app ">whiteboard </a> instead of using colors (or using white chalk on the blackboard instead of colored chalk)
2. making copies of handouts with a high black/white contrast, and not on colored paper
3. using patterns and/or labels in addition to colors
4. writing out the names of colors if they are relevant to instruction (yellow sun, green frog, etc.)
5. making sure art supplies or other supplies with colors are appropriately labeled
6. If you think a student may be color blind, talk to the family about getting their child tested.