Chromostereopsis

Different wavelengths or colors of light are bent different amounts by a simple lens or prism. This leads to an interesting effect of the eye called chromostereopsis.

Chromostereopsis is what we perceive visually when two colors are placed side by side. When bright blue and bright red are next to each other, one will look in focus while the other will look slightly out of focus. Generally, it is irritating to a viewer's eyes and doesn't look good either. Also, the red will look closer than the blue.

In 1885, W. Einthoven was the first scientist to study the chromostereopic effect. There is a difference between the visual and optical axes. Therefore, light from the fovea will hit the corneal surface at an angle, causing a prism effect. Blue, with its shorter wavelengths, is refracted more than red with its longer wavelengths. Blue light is focused toward the nose, making it appear farther than red which is focused toward the temple.