Color Blindness: Causes, Types, and Testing

What Causes Color Blindness?

Color blindness is a condition in which a person has difficulty seeing red, green, blue, or a combination of these colors. In rare cases, a person may see no color at all. Color blindness is more common in males than females and is typically genetic—passed on from parent to child.

Genetic color blindness is caused by a mutation on the X chromosome. Since males have only one X chromosome, around 8% of men are affected, compared to just 0.5% of women.

Scientifically, cone cells in the eye—about 6 to 7 million of them—control color sensitivity. Different cones (red, green, and blue) are responsible for interpreting different wavelengths of light. These cells are concentrated in the macula, at the center of the retina. If a person is missing one type of cone cell or has malfunctioning cones, they may experience altered or reduced color perception.

Though most people with color blindness are born with it, the condition can also be acquired later in life due to injury, aging, certain medications, or other eye diseases.

 

What Are the 4 Types of Color Blindness?

Color blindness is commonly classified into three major types, though four are often recognized when including total color blindness:

1. Red-Green Color Deficiency – The most common type, further divided into:
   – Protanomaly (reduced sensitivity to red light)
   – Deuteranomaly (reduced sensitivity to green light)
2. Blue-Yellow Color Deficiency – Also known as tritanomaly or tritanopia.
3. Total Color Blindness – Known as monochromacy, where a person sees only in shades of gray.
4. Cone Deficiency Variants – Other rare forms involving malfunction of multiple cone types.

Most people with color vision deficiencies fall into the red-green category, which accounts for the majority of cases.

 

What Type of Colorblind Am I?

To determine what type of colorblindness a person has, eye care professionals rely on specialized diagnostic tests. These tests assess how an individual perceives different colors and hues and help classify the specific deficiency.

 

How to Know If You Are Colorblind?

Many people with color vision deficiency don’t realize it until a situation arises that reveals their difficulty. Some common signs include trouble distinguishing traffic lights, matching clothes, or identifying colored charts or graphs.

Color vision problems often make reading, and sometimes even learning in general, more challenging. In some cases, it may limit career options in fields that rely on color discernment such as design, aviation, or electrical work.

 

Color Blindness Tests

There are two commonly used tests to diagnose and evaluate color blindness:

Ishihara Color Test – Developed in 1917 by Dr. Shinobu Ishihara, this test remains the most widely used. It consists of 38 plates with colored dots forming numbers or letters. Most color vision issues are detected within the first few plates, while the full set is used to assess severity.

Farnsworth D-15 Test – Created in 1947 by Navy Commander Dean Farnsworth, this test requires individuals to arrange colored discs or chips in order of hue. It helps determine the type and severity of color vision deficiency.