Color blindness, also known as color vision deficiency, is a relatively uncommon eye condition. Since it's not life-threatening and rarely comes with other indications, people with color blindness often go through life unbothered. Sometimes, they may go for years without knowing they can't see certain shades and hues. In this publication, we are exploring the types of color blindness.
What is Color Blindness?
Color blindness is a condition where individuals have difficulty distinguishing between certain colors.
The issue arises from anomalies in the photoreceptor cells in the retina called cones, which are responsible for color vision.
There are three types of cones. Each is sensitive to different wavelengths of light: red (long-wavelength), green (medium-wavelength), and blue (short-wavelength).
Normal color vision requires all three types of cones to function correctly. When one or more types of cones do not work as expected, color blindness occurs.
Color Blindness Causes
Color blindness can be inherited or acquired.
Inherited color blindness is usually caused by genetic mutations. They are passed down through the X chromosome, making it more common in men. But still, it's not gender exclusive.
Acquired color blindness can result from:
Aging: Changes in the eye's lens.
Diseases: Conditions such as diabetes, glaucoma, macular degeneration, multiple sclerosis.
Medications: Certain heart, blood pressure, and infection treatments.
Chemical Exposure: Substances like carbon disulfide and styrene.
These factors can impair the function of the photoreceptor cells in the retina, leading to difficulties in distinguishing colors.
Main Types of Color Blindness
The type classification of color blindness depends on which cones are affected and how they function.
The primary types of color blindness include:
Red-Green Color Blindness
Blue-Yellow Color Blindness
Complete Color Blindness
1. Red-Green Color Blindness (Daltonism)
The condition affects the perception of red and green hues.
Red-green color blindness is the most common form, also known as Daltonism. This color blindness is named after the English chemist John Dalton, who first studied his own color perceptions.
1.1. Protanopia and Protanomaly (Red Color Blindness)
Protanomaly (anomalous trichromacy) and protanopia (dichromacy) are sub-types of red-green color blindness affecting the red cones (L-cones).
Protanopia: - In protanopia, the red cones are absent. - People with the condition cannot perceive red light. - Confusion of red color with green or brown.
Protanomaly: - Individuals have abnormal red cones and are less sensitive to red light. - Difficulty distinguishing between red and green and lower brightness of red shades.
1.2. Deuteranopia and Deuteranomaly (Green Color Blindness)
Deuteranomaly and deuteranopia are sub-types of red-green color blindness affecting the green cones (M-cones).
Deuteranopia: - In deuteranopia, the green cones are absent. - People with this color blindness can't recognize green light - Confusion of green color with red or yellow.
Deuteranomaly: - Those with deuteranomaly have abnormal green cones and are less responsive to green light. - Confusion between red and green hues, similar to protanomaly.
The Ishihara test is a widely used diagnostic tool for the colorblind. The test includes a series of plates with colored dots forming numbers or shapes. Each plate is designed to identify specific types of color blindness.
2. Blue-Yellow Color Blindness
Blue-yellow color blindness is less common than red-green color blindness. It involves difficulty distinguishing between blue and yellow hues.
Unlike red-green color blindness, which is often called Daltonism, there is no widely recognized alternative name for blue-yellow color blindness.
2.1. Tritanopia and Tritanomaly
Tritanomaly and tritanopia affect the blue cones (S-cones).
Tritanopia: - In tritanopia, the blue cones aren't present at all. - Individuals can't perceive blue light. - Confusion between blue and green; and between yellow and violet.
Tritanomaly: - People with tritanomaly have abnormal blue cones, less sensitive to blue light. - Difficult to distinguish between blue and green; and between yellow and red.
The Ishihara test primarily focuses on Daltonism, but some variations of the test may include plates for detecting blue-yellow color blindness. These are less common and supplemented with other tests, like the Farnsworth-Munsell 100 Hue Test.
3. Complete Color Blindness (Monochromacy)
Complete color blindness, or monochromacy, is a rare condition where individuals see no color.
3.1. Monochromacy
Monochromacy occurs when two or all three types of cones are non-functional.
Blue Cone Monochromacy: - When both red and green cones are non-functional, leaving only blue cones active. - Individuals see the world in shades of blue and cannot distinguish between colors that require red or green cones.
Achromatopsia: - A rare and severe form of color blindness affecting all three types of cones. - Only the rod cells, responsible for vision in low light, are active. - Perception of the world in black, white, and shades of gray. - It often comes with other visual impairments like light sensitivity (photophobia) and poor visual acuity.
In Summary
From the more common red-green color blindness to the rarer blue-yellow and complete color blindness, each type presents unique challenges. While there is no cure, various strategies, assistive technologies, and ongoing research provide hope and support for colorblind individuals.
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Checked by Atanas Bogoev, MD.