WE PERCEIVE OBJECTS THANKS TO THE LIGHT THEY REFLECT. THE RAYS PASS FIRSTLY THROUGH THE CORNEA AND THE LENS, WHICH THEN DIRECT THEM TO THE RETINA WHERE THE IMAGE IS 'DECODED'.

HOW DOES SIGHT WORK ?

The eye works in much the same way as a camera. Light reflected by the object we are looking at converges towards the cornea and the lens, forming a reverse image on retinal photoreceptor cells. These cells transmit the information they have received to the brain via the optic nerve. The brain interprets and recomposes the image. (see animation).
The iris controls the quantity of light penetrating the eye. At the centre of the iris is the pupil, a black opening that expands and shrinks to control the quantity of light penetrating the eye. The human eye provides the best sight when it is perfectly spherical. Distortions occur when the eye or the cornea is slightly ovoid in shape; they include common disorders such as astigmatism, myopia and hypermetropia. Such disorders are often hereditary; their cause is not known. They can be treated, but not prevented. Presbyopia, linked to the ageing of the eye, is another disorder that cannot be warded off.