How does sight differ in animals ?

Man has two eyes but there are other animals which have more or even less !
One-eyed animals - The Euglena, which is a protozoan, has only one eye.
Four eyed animals - The four eyed fish seems to have four eyes. Actually there are only two eyes. Each of is them split into two. This is to help them to look above the water level for insects as well as below, to escape predators.
Five-eyed animals - There are some insects which have five eyes. They have three simple eyes and two compound eyes. Compound eyes consist of thousands of minute eyes packed closely together. Examples of such insects are the butterfly and the honeybee.
Eight-eyed animals - The maximum number of eyes found in animals is eight. This is found in the wolf spider.
Of all the animals, the birds of prey like the eagle and owl, have the sharpest sense of sight.