A
simple eye (sometimes called a
pigment pit) refers to a type of
eye form or optical arrangement that contains a single lens. A "simple eye" is so called in distinction from a multi-lensed "
compound eye", and is not necessarily at all simple in the usual sense of the word. The
eyes of humans and large animals, and
camera lenses are classed as "simple" because in both cases a single lens collects and focuses light onto the
retina or
film. Many
insects have compound eyes consisting of multiple lenses (up to tens of thousands), each focusing light onto a small number of retinula cells.