What is Color Blindness? - Causes & Overview

Instructor: Natalia Caporale
Humans have an incredibly sensitive and sophisticated visual system. Color blindness is a visual disorder characterized by a deficiency in color detection or processing. Here we explore several types of color blindness and their causes.

Color Blindness: Definition

Did you know that 8% of males and 1% of females are unable to detect or discriminate between one or more colors? This condition is known as color blindness, and it comes in a few different forms. Sometimes, it affects an individual's ability to see certain colors, like red or green. Other times, it makes it difficult for individuals to discern between colors at all. But what causes color blindness in the first place?

How Do We See Colors?

As human beings, we have the incredible capacity to detect electromagnetic energy (light) and transform it into meaningful visual images. This formidable task, which cannot yet be replicated by any computer in the world, depends on the correct functioning of our eyes as well as several brain structures devoted to visual information processing.

In our eyes, we have specialized cells called photoreceptors that function as light-detectors. Of these, rods are the most abundant and most sensitive to light, whereas cones are specialized for detecting specific wavelengths of light (which we perceive as colors), but can only function at relatively high illumination levels. If we had no cones, we would perceive the world to be made of different shades of gray (Figure 1). In fact, if you look at a color image in a very weakly illuminated room, the image will look grayscale to you! This is because only the rods would be active at such low illumination levels. (Try it out and see!)

Figure 1. A) Image in full colors. B) Grayscale version of the same image.
 Example of Grayscale Image

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