The phylogenetic evolution of the visual system
pp. 1-12
in: Virginio Cantoni (ed), Human and machine vision, Berlin, Springer, 1994Abstract
The first eye could only tell light from dark, then motion, colours and forms became visual images. Through phylogenetic evolution a large number of visual systems have been originated and shaped to increase general efficiency and to adapt to the available ecological niches. The compound eyes of invertebrates are best at short distance sight. Their field of view is almost spherical. Many invertebrates can see from ultraviolet to infrared, and detect the plane of polarisation of light. Vertebrates have developed different visual structures to achieve high acuity and accommodation. The retina of fish, the ancestors of all vertebrates, is a mini-brain performing complex visual tasks as motion detection and is an example of ongoing adaptation to different environments; during development retinal cells modify to adapt to changes in habitat and habit. In higher vertebrates retinal processing is greatly reduced and substituted by the much more efficient central processing. Extended colour vision and detection of polarised light are lost in humans, but we can tune our vision to read a book or to look at the stars.