Color Blindness: How the Eye Perceives Color

Color blindness may result from a genetic disorder, injury, illness, or age. Failing to recognize, match, or perceive the intensity of colors are common symptoms. 

The different types include dichromacy, monochromacy, and red-green color blindness. The proper diagnosis and form of treatment depend on the type of color blindness.

What Is Color Blindness?

Red-green color blindness is the most common. In some instances, the eye perceives all colors as shades of gray.

Symptoms of Color Blindness

Symptoms of color blindness vary depending on the type. 

  • Difficulty seeing colors in a dark or bright light: A person experiencing mild color vision deficiency might identify colors in dim lighting. If the condition is severe, the person won’t see colors in dark and bright light.
  • Not recognizing the same colors when looking at them side by side: Some medical conditions or injuries can lead to color blindness in one eye only. A difference in eye receptors causes a slight difference in color perception. As a result, both the left and right eyes see different colors.
  • Difficulty matching colors: When specific colors mix, a colorblind person can’t tell them apart. It’s a common symptom of red-green color blindness. 
  • Failing to perceive the intensity of colors: Protan color blindness causes colors to appear darker or lighter than their actual shade. For instance, the eye may not distinguish pink, red, or maroon on a color palette.

Common Causes of Color Blindness

  • Genetic Mutations
  • Age
  • Optic Nerve Damage
  • Certain Diseases and Medications
  • Exposure to Some Chemicals or Toxins
  • Trauma or Injury to the Eye
  • Vitamin A Deficiency
  • Cataracts
  • Glaucoma

Types of Color Blindness

Types of Color Blindness

The types of color blindness vary depending on the inability to perceive color. Colorblind individuals are less sensitive to green, red, or blue light and their secondary colors.

Color vision deficiency/ Dichromacy

Dichromacy is where one has two types of cone cells instead of three under normal color vision. Because only two cone receptors are functional, a dichromatic person will distinguish only two primary colors.

While losing the S cone is rare, losing the L and M cone function is more common. Losing the latter functions is caused by a genetic mutation in the X-chromosome.

For this reason, it affects men the most. Depending on the absent cone, dichromacy is split into three types: deuteranopia, protanopia, or tritanopia.

Blue-Yellow Color Deficiency

Blue-yellow color blindness, or tritanopia, makes distinguishing between blue and green challenging. Affected individuals also can’t identify yellow from pink and purple from red. The condition occurs due to the short-wavelength cone (S-cone) loss.

The S-cone receptors are present but defective for some individuals due to a genetic mutation. It’s a type of blue-yellow color blindness known as tritanomaly. Tritanomaly makes blue and green and yellow and red look similar.

Red-Green Color Deficiency

Red-green color blindness makes it hard to distinguish red from green. It’s split into four types: deuteranopia, protanopia, protanomaly, or deuteranomaly. Individuals with deuteranopia are blind to the color green. Deuteranopia occurs due to the loss of the M cone function.

Protanopia is an anomaly of the L cone function, making red colors look green and dull. Protanomaly and deuteranomaly are severe types of red-green color blindness. The L and M cones are absent, making red and green colors blurry and shadowy.

Fully Color Blind/ Monochromacy

Rod monochromacy is a rare type of color blindness when all cone receptors are non-functional. Full-color blinds lack color vision and see all colors as shades of gray.

For blue cone monochromacy, only one cone receptor works. Monochromats also suffer from poor vision, photophobia, and nystagmus (involuntary eye movement).

Treatments for Color Blindness

Color vision tests for adults and children help determine if an individual suffers from color blindness. Besides the Ishihara test, optometrists use color plates and an anomaloscope for diagnosis.

Color blindness due to genetics is non-reversible. But, various treatments cure color blindness that emanates from other health conditions.

1. Intensive Color Vision Therapy

Intensive color vision therapy (ICVT) is an advanced treatment that helps improve color perception and vision. The treatment method relies on systematic exposure to light and color.

It helps people with color perception improve various visual aspects, such as brightness and hue discrimination. Intensive color vision therapy re-conditions visual pathways through repeated stimuli.

2. Color Corrective Contact Lenses and Glasses

Color corrective glasses and lenses help people with color vision deficiency recognize different colors. Notable brands, such as EnChroma and Pilestone, make glasses for each type of color blindness.

The glasses work by blocking out specific wavelengths. Soft contact lenses and glasses make it easy to distinguish between colors. But, visual aids are effective in severe cases and may not work for some individuals.

3. Color Contrast Techniques

Color contrast techniques involve mixing colors like yellow and purple or black and white. These techniques create colors with enough contrast to help those with color blindness easily distinguish them.

People with red-green color blindness can differentiate between blue and yellow since they’re high-contrast colors. Using high-contrast combinations improves the visibility of text and images.

4. Color Filters

Color filters reduce the effects of color blindness. They alter the colors that a person with color blindness perceives. The color filters block specific light wavelengths to change colors that reach a person’s eyes. They’re often worn as glasses, while some are embedded into smartphones or computer screens.

5. Assistive Technology (Color-Correcting Software)

Color-correcting software is a form of assistive technology that helps treat color blindness. It processes images and videos in real-time and adjusts the colors to a palette.

The software identifies and corrects problematic colors to enhance the distinction between colors. Color-correcting software is compatible with computers and mobile devices. It assists colorblind professionals in fashion, advertising, and graphic design.