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hat is color blindness? A color festival. No. Color blindness or color deficiency is a vision problem. Now, our eyes have light sensitive cells called rods and cones. Can I put ice cream on these cones? You are just unbelievable. Rods are responsible for black and white vision. They do not detect color. Whereas, cones detect color. There are three types of cones. One cone perceives red light, another perceives green and the third perceives blue. Together, these cones help us to see the whole spectrum of colors. Now in some cases, when one or more types of cones do not work properly, it causes color blindness. People with such deficiency have difficulty in distinguishing between certain colors or shades. For example, in red-green color blindness, the apple tree may appear like this.

Normally, male squirrel monkeys can't distinguish between red and green hues-they're what is called color-blind in humans. The South American Saimiri genus lacks a gene that allows color-sensitive cells in the eye, called cones, to differentiate red and green from gray. To these animals, other colors, such as blue, brown and orange, appear faded. But Sam was one of two males in the experimental group of a groundbreaking 2009 ophthalmological study conducted at the Washington National Primate Research Center in Seattle. Husband-and-wife vision researchers Jay and Maureen Neitz injected a viral vector behind the retinas, the part of the eye that responds to color, of Sam and his simian lab partner, Dalton. The virus contained the genetic code in human eyes for red pigment, giving the monkeys an extra class of cone photoreceptor.

Some people in the world aren't able to see many colors. The condition is called color blindness, but what exactly causes it?

infographic on vision including color blindness