Understanding Color Blindness

Eye care professional screens child for color vision defects.

Color blindness refers to the inability to see differences in certain colors which can be discerned by others. Typically, people who suffer from color blindness cannot tell red from green or the colors appear somewhat differently to them. About 10 million men in America suffer from color blindness. Color blindness affects a great number of people across the world. With the right education and management, they can learn to improve their color vision deficiency.

Trichromatic Color Vision

Trichromatic color vision is a theory which explains how humans and some other animals see color. In the retina, there are three receptors that interact to create different colors. Each of these receptors is singularly sensitive to the color blue, the color green, and the color red. The combination of these three colors produces a color in the visible spectrum.

• Trichromatic Color Vision in Primates: Scientific study on how primates see color.
• Trichromatic Theory of Color Vision: Explains the phenomenon in diagrams and statistics.
• The Perception of Color: Discusses how primates perceive color.
• Theories of Color Vision: A look at the trichromatic theory and the opponent-process theory.

Color Vision Deficiency

Color vision deficiency is another term for color blindness. Most people who are color blind cannot see certain shades of colors, most notably, greens and reds. Deuteronanomaly is the deficiency in seeing greens. Protonamlay is the deficiency in seeing reds.

• Color Vision Deficiency: An overview covering the causes, diagnosis, and treatment.
• Genetic Conditions: Discusses the genetic conditions which cause color blindness.
• Color Blindness: Provides information on the condition.
• Types: Highlights the different types of color vision deficiencies.

Monochromacy

Monochromacy is another term for “total color blindness”. Rod monochromacy refers to the condition whereby there are only rods in the retina. Rod monochromats are completely color blind so they can only see things in shades of grey. Cone monochromacy refers to the condition whereby rods and cones are present in the retina but there’s only one type of cone, instead of three.

• Overview: An overview of color blindness, touching on monochromacy.
• Types of Color Vision Deficiencies: Discusses the different types of deficiencies including monochromacy.
• Achromatopsia: Explains the condition with reference to rod monochromacy and cone monochromacy.
• Blue-Cone Monochromats: Provides information on blue-cone monochromacy.
• Cone Dystrophies: Discusses cone dystrophies and cone monochromacy.

Dichromacy

Dichromacy is not as severe as monochromacy so dichromats can perceive some hues. Protanopia is a color vision deficiency in which there are no red receptors in the retina. Deuteranopia is a deficiency in which there are no green receptors in the retina. In tritanopia, there are no blue receptors in the retina.

• Dichromacy: Provides vital information on dichromacy.
• Definitions: Defines protanopia, deuteranopia, and tritanopia.
• Deuteranopia Simulation: Simulates the vision of a deuteranope.
• Color: Shows how dichromats see different colors.

Anomalous Trichromacy

Trichromats can perceive hues better than dichromats, but they still cannot see color like normal people. Protanomaly is associated with a “red weakness” so protanomalous individuals are not so sensitive to red light. The most common type of color blindness, deuteranomaly is associated with a “green weakness”. Tritanomaly refers to a weakness in perceiving between blue and yellow.

• Anomalous Trichromacy: Explores the causes and incidences of color blindness.
• Protanomaly: Provides some information on the condition.
• Deuteranomaly: Briefly touches on this type of color blindness.
• Color Vision: Discusses human color vision with section on anomalous trichromacy.

Causes of Color Blindness

Color blindness can be caused by a number of factors. Studies have shown that it’s commonly linked to genetics and sex. A larger proportion of males have been found to be color blind in comparison to females. Color blindness may also be caused by other factors like exposure to some chemicals, aging, eye injuries, eye problems, brain damage, or side effects from consumption of certain medicines.

• Causes: Looks at some of the causes of color blindness.
• Symptoms & Causes: Factsheet on color blindness with information on symptoms and causes.

Tests & Diagnosis

There are some tests that can be used to determine color blindness. Possibly, the most well-known test is the Ishihara Color Test. The subject has to differentiate the numbers on different colored plates consisting of a circle of dots. Color vision deficiency is diagnosed if the subject is unable to pick out the numbers from the plates.

• The Ishihara Color Test: Take the test to find out if you are color blind.

Management

Presently, there’s no cure for hereditary color blindness. Some forms of acquired color blindness can be made better with surgery. There are also tinted eyeglasses and contact lenses which can help to make it easier to see the differences between colors. Color vision deficiency can be reduced by wearing glasses that reduce glare.

• Treatments: An overview of some treatments for color blindness.