Sight is one of our most complex senses. But did you ever wonder just how eyes work? Our eyes work similar to a camera, in which light enters through an opening(pupil), with a lens for focusing and a light-sensitive membrane(retina) at the back.
The amount of light that enters the eye is controlled by muscles in the iris, which contract and relax to altering the size of the pupil. The light first passes through the cornea, and then moves into the lens, which bends the light, focusing it to a point on the retina, at the back of the eye.
After the light passes through your pupils and crystalline lens, it focuses on the retina. The retina is covered in millions of light-sensitive receptors known as rods and cones. Each receptor contains pigment molecules, which change shape when they are hit by light, triggering an electrical message that travels to the brain via the optic nerve. When photons of light hit the pigments inside the cells, it triggers a cascade of signals, which pass through a series of different connections before they are transmitted to the brain.
The surprising part is, the images formed are upside down in the back of your eye! Your brain processes this information and flips the images again so that we see the world right side up. Although our eyes can only detect green, blue and red wavelengths of light, the brain combines and creates millions of different shades. Three-coloured vision is unique to human beings.
Our eyes can produce two-dimensional images, but the brain processes to build these flat pictures into a three-dimensional view. The eyes are positioned about two inches apart, such that each sees the world from a slightly different angle. The brain compares the two pictures, using the differences to create the illusion of depth.