Eyes

Eyes are the organs of vision. They detect light and convert it into electro-chemical impulses in neurons. In higher organisms, the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in molluscs, chordates and arthropods.

This is the hardware system.  Coupled with this hardware is an equally complex software system that makes sense of those images.  This software system combines the images from the two eyes to make an apparently 3D picture to help us navigate the environment and also helps us by filtering out non-essential data.  There is the real possibility, for example, that our hardware eyes could pick up the same sorts of images at a distance as a hawk can, but as a human being there is no advantage to us to have images this detailed from so far away.  Thus the eye software tends to home in on the processing of things nearer to us.

Dogs are able to ‘see’ only moving objects.  But their software system is far better than ours at picking up that movement and co-ordinating it with their body movements, which is why a dog can catch a flying Frisbee with ease, whereas we can’t.

Possessing detailed hyperspectral colour vision, the Mantis shrimp has been reported to have the world's most complex colour vision system.