The eye is the body’s organ for perceiving optical information. It detects visible light having a wavelength between 380 and 700 nm (the wavelength of light is expressed in nm or nanometers, one nanometer is a millionth of a millimeter). Below 380 nm is UV light, which is extremely harmful to the eye as it can irreparably damage it. Glasses that block UV light are recommended – especially sun glasses should be of good quality to avoid eye damage. Above 700 nm is IR (infrared) light or heat radiation which is also dangerous to the eye.


The path of view begins with the reflection of light from the observed object. Light travels through the cornea, where the refraction of light begins, to the pupil. This is an opening in the iris that changes diameter and thus regulates the amount of light that penetrates the eye – in strong light it can be narrowed (2mm), in low light conditions it opens up to 8mm. The light then refracts in the lens of the eye, crosses the clear glass, and refracts in the yellow spot. It contains photoreceptors that, under the influence of light, send electrical signals through nerves to the optical center in the brain, where an image is created and processed.

Eye irregularities

Anatomy of human eye
Normal vision (ementropa)
Viewing at different distances
Farsightness and shortsightness