It is difficult for most people to imagine everyday life without the use of their eyes, our perception of the world is first and foremost visual and our image and awareness of our own being is primarily from a perspective centred 'behind' our eyes. It is easy to assume that every creature which can see does so in the same way but this is not the case, eyes come in a variety of shapes, sizes and designs from the ocelli of the snail, capable of distinguishing only light and dark to the detailed hyperspectral colour vision of the Mantis shrimp, the most complex visual system yet to have evolved.
Most experts consider that the eye as an organ of vision has evolved monophyletically, that is to say that all eyes originate from a single species with a proto-eye thought to have evolved approximately 540 million years ago. In spite of this immense period of time most of the developmental process is thought to have taken place within a relatively short period of only a few million years as the selective advantage provided by sight precipitated a burst of intense competition as competing organisms had to match the capabilities of others in order to survive. This has resulted in the development of a number of different eye types each adapted to serve the requirements of the organism in question.
Disclaimer: The author is not a medical doctor, optician, ophthalmologist or any other medical professional, this article has been compiled using a variety of internet reference sources and while every effort has been made to ensure accuracy this cannot be guaranteed. No preference for product or brand is inferred or intended and the contents of this article are not to be used in whole or in part to inform a decision regarding any aspect of contact lens use.
