Your eyes are simply extraordinary. Making approximately 200,000 movements per day, they are able to distinguish around 10 million colours. The eye is an incredibly complex organ that reacts to light, processes it and transmits it to the brain, allowing you to ‘see’.
The eye is an extraordinary and complex organ that allows us to ‘see’. The brain actually does the ‘seeing’ – the eye is the ‘central processor’ that takes the information in the form of light waves and transmits the information into the brain.
How vision works
Vision occurs when light enters the eye through the pupil. With help from other important structures in the eye, like the iris and cornea, the appropriate amount of light is directed towards the lens.
Just like a lens in a camera sends a message to produce a film, the lens in the eye ‘refracts’ (bends) incoming light onto the retina. The retina is made up by millions of specialised cells known as rods and cones, which work together to transform the image into electrical energy, which is sent to the optic disk on the retina and transferred via electrical impulses along the optic nerve to be processed by the brain.
The cornea is the clear portion of the eye that covers the iris and the pupil and takes up about one-sixth of the eye. The rest of the eye (the scleral segment) is opaque. Several nerves and blood vessels run through the sclera, including the optic nerve. The cornea and scleral segment come together in an area called the limbus. This contains a great deal of blood vessels.
The Iris and Pupil
The iris and pupil are the most noticeable parts of the eye. The iris is the coloured ring of tissue that lies beneath the cornea and can be a range of colours, determined by genetics. The pupil is located in the centre of the iris and appears as a black hole that acts rather like a camera aperture, allowing light to enter the eye. This works in the same way as a camera, adjusting to control the flow of light into the eye. In bright conditions, the pupil closes down, reducing the amount of light entering the eye and protecting the delicate nerves from being damaged. In the dark, the reverse happens to allow what light there is to enter the eye.