What color-blind people see and don't see can vary based on what rods and cones of the eyes are affected. Rod and cones are photoreceptor cells that deliver information that the brain interprets as color and shade. Cones detect red, blue, and green colors, while rods describe lightness and darkness. If any of these cells are not functioning as they should, color blindness can occur.
Color-blind people see differently depending on what form of color blindness they have. Some people may not be able to tell certain colors from others, or the colors may appear muted or washed out. In rarer cases, someone who is color blind may not see any color at all.
This article describes the various types of color blindness and what causes them. It also explains how color blindness is diagnosed and how color-blind people adapt to situations where color might otherwise seem essential.
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How Color Blind People See Color
Color blindness doesn't always mean a person only sees in shades of gray. This type of color blindness is considered the most severe, but it's uncommon. Most people with color blindness simply see a narrower range of color than someone with full-color vision. What this means in terms of their vision can differ.
People with color blindness may:
- Confuse certain colors: For example, the color red may look the same as the color green.
- Have difficulty seeing colors in certain light: Some people with mild color blindness can see colors normally in good light but not in dim light.
- Not see certain or any color no matter the light.
Does Color Blindness Get Worse?
Color blindness is usually something you are born with that remains stable throughout life. Color perception can change with age, but any sudden or significant change may indicate a serious health concern requiring the attention of a healthcare provider.
How Types of Color Blindness Affect What Someone Sees
There are several different types of color blindness based on which cone (or cones) in the eye are affected. Each type affects color vision in a specific way.
Color blindness usually affects both eyes but can sometimes affect one eye, a condition referred to as unilateral color blindness orunilateral dichromacy. It is more often caused by an injury or disorder in later life and less likely to be the result of a congenital abnormality you are born with.
Red-Green Color Blindness
The most common type of color blindness is red-green color blindness which affects the ability to distinguish between red and green. It occurs in about one in 12 males and one in 200 females of northern European ancestry.
There are four types of red-green color blindness:
- Protanomaly: This causes red colors to look green due to malfunctioning red cones.
- Protanopia: This causes red colors to look green due to nonfunctioning or missing red cones.
- Deuteranomaly: This causes green colors to look red due to malfunctioning green cones.
- Deuteranopia: This causes green colors to look red due to nonfunctioning or missing green cones.
Red-Green Color Blind Tests
Blue-Yellow Color Blindness
Blue-yellow color blindness, also called tritan defects, is a less common type of color blindness in which you cannot differentiate between blue and green, yellow and red, or dark blue and black. It affects one in 10,000 people worldwide. Males and females are equally affected.
There are two types of blue-yellow color blindness:
- Tritanomaly: This makes it difficult to tell the difference between blue and green and between yellow and red due to malfunctioning blue and yellow cones.
- Tritanopia: This makes it difficult to differentiate between blue and green, purple and red, and yellow and pink due to nonfunctioning or missing blue and yellow cones. It also makes colors look less bright.
Blue Cone Monochromacy
Blue monochromacy is an uncommon and severe form of color blindness in which you are unable to see any color. It affects about one in 100,000 people worldwide and occurs at a higher rate in males than females.
Instead of seeing color, people with this type of color blindness view the world in shades of gray. They also have additional vision problems, such as:
- Increased light sensitivity (photophobia)
- Involuntary eye movements (nystagmus)
- Nearsightedness (myopia)
Blue cone monochromacy may be a component ofachromatopsia (a partial or total lack of color vision with other vision problems).
Distinguishing Colors With Color Blindness
What Causes Color Blindness?
The three primary colors in the light spectrum—red, yellow, and blue—have different wavelengths. The retina, in turn, contains three types of cones that react to the different wavelengths. The activation of these cones transmits information to the brain which is translated into color. When one or more of these cones are malfunctioning or nonfunctional, color blindness can occur.
Color blindness may be something you are born with or something that develops later in life.
Genetic Color Blindness
Genetics are largely responsible for color blindness. Three specific genes are responsible for producing different pigments (called opsins) that react to different wavelengths of light:
- OPN1LWgene produces opsins for long-wavelength cones (L cones). Red is the color with the longest wavelength.
- OPN1MWgene produces opsins for middle-wavelength cones (M cones). Yellow is the color with a medium wavelength.
- OPN1SWgene produces opsins for short-wavelength cones (S cones). Blue is the color with the shortest wavelength.
Mutations of the OPN1LW or OPN1MW gene can cause red-green color blindness in different ways:
- Deuteranomaly happens when opsins in M cones are flawed or inadequate.
- Deuteranopia occurs when opsins in M cones are nonfunctional or missing.
- Protanomaly happens when opsins in L cones are flawed or inadequate.
- Protanopia occurs when opsins in L cones are nonfunctional or missing.
Blue-yellow color blindness can be caused by mutations of the OPN1SW gene. People with this type of color blindness either have malfunctioning or nonfunctional S cones.
Blue cone monochromacy happens when mutations of the OPN1LW and OPN1MW genes affect both the L and M cones.
Acquired Color Blindness
People are usually born with color blindness, but color blindness can happen later in life if your eyes or parts of your brain involved with color are damaged.
Acquired color vision deficiency can be caused by:
- Eye diseases, like glaucoma or macular degeneration
- Neurodegenerative diseases, like Alzheimer’s disease or multiple sclerosis
- Certain medicines, like Plaquenil (hydroxychloroquine) used to treat malaria
- Eye or brain trauma, including stroke
- Normal aging, especially with cataracts
Can Women Be Color Blind?
How Is Color Blindness Diagnosed?
Color blindness can be diagnosed by an eye specialist called an ophthalmologist or a related healthcare professional called an optometrist. (An optician is a non-medical technician responsible for filling prescriptions from an optometrist or ophthalmologist.)
The eye specialist can diagnose color blindness based on three different visual tests:
Color Plate Test
This is the most common test used for color blindness and is usually the only test needed to make the diagnosis.
For this test, you are asked to look at an image made up of colored dots with a differently colored number or shape in the middle. If the number or shape blends into the background and you cannot see it, you may have color blindness. Different color plates can detect different types of color blindness.
Anomaloscope
This is a microscope-like device you look into that has two different lights set at different brightness. You will be asked to adjust a knob to get the two different brightness to match. If you are unable to match them, then you may have problems with the rods in your eyes.
Since lightness and darkness factor into different shades of color, problems with your rods can contribute to color blindness.
Hue Test
In a hue test, you are given 10 blocks of different colors and be asked to arrange them in ascending order from the lightest shade (like pink) to the darkest (like violet). If you have trouble putting them in order, you may have color blindness.
The hue test is often used after a color plate test to better determine which type of color blindness you have. Different sets of blocks are designed specifically for the different types of color blindness.
Eye specialists often use this test for people who need accurate color vision for their jobs, like photographers, web designers, and pilots.
Adjusting to Being Color Blind
Living with color blindness can be hard. People with color blindness have trouble performing daily tasks that require them to tell the difference between colors. Examples of some daily activities that affect color-blind people are driving, coordinating outfits, using gadgets, and preparing meals.
Nevertheless, it is possible to live normally with color blindness by changing some daily routines, including:
- Memorizing patterns: Activities like driving can be difficult, especially when you can't see the colors in a stoplight. Paying attention to the position of the lights helps you know what to do.
- Altering the lighting at your home or office: Working in a dark or poorly lit space makes it harder to see with color blindness. Daylight bulbs can brighten your environment.
- Labeling your clothes: A labeling system, such as writing the color of the garment on the tag, can help you coordinate your outfits.
- Using your other four senses: Utilize your senses of smell, touch, taste, andhearing. For example, choose fresh fruits from the grocery store by using touch and smell.
Research has shown that color recognition isn't necessary for safe driving. Road signs are still distinguishable because of their shapes, patterns, and symbols. Similarly, traffic lights follow a pattern that color-blind drivers can follow: red on top, yellow in the middle, and green at the bottom.
Certain types of eyeglasses can help color-blind people see some colors. If you have color blindness, talk to your healthcare provider about ways to manage color blindness.
Summary
Color-blind people don't always see in shades of gray. In fact, this form of color blindness is rare. Instead, most people with color blindness see a limited range of colors.
Red-green color blindness makes it hard to tell the difference between red and green. Blue-yellow color blindness is less common and makes it hard to distinguish between blue and green, yellow and red, and dark blue and black. Blue cone monochromacy is a severe, rare type in which don't see any color at all.
Color blindness can be diagnosed with a color plate test, a hue test, and an anomaloscope administered by an ophthalmologist or optometrist.
