Visual perception: a complex mechanism

Nothing is more natural than vision... and yet! Capturing light and transforming it into a meaningful visual scenario presents enormous technical challenges.

The eye must first obtain a perfectly focused image of the outside world on the retina, which requires an elaborate optical system (composed of the cornea, the crystalline lens and the iris diaphragm). Next, the nervous system (retina, visual pathways and brain) must faithfully transmit this image from the eye to the brain. Finally, the brain has to re-elaborate the information received, so that it emerges in the form of an image.

The most advanced camera ever!

The eye, the sensory organ responsible for visual perception, could be compared to a video camera equipped with: software that automatically tracks objects entering its field of view, an autofocus system, a mode that automatically adapts to changes in light intensity, and a self-cleaning lens.
All of this is connected to a computer system with such sophisticated information processing capabilities that no computer currently exists that can match it.

The cornea: responsible for lighting

The cornea is a kind of window through which light from the outside enters our body. It plays a key role in focusing light on the retina. For this reason, it must always be perfectly clean and transparent. Regular closure of the eyelids (blinking) and lacrimal secretion keep the surface of the cornea free of impurities.

The crystalline lens: a "zoom" role

The main function of the lens is to enable the necessary adjustments for focusing on objects at all distances. This focusing is achieved by changing the curvature of the lens, either by tightening or relaxing the tendons that attach the lens to the inner wall of the eyeball. The lens bulges to focus on nearby objects and becomes flatter (resting position) to bring distant objects into focus.
The pupil: the diaphragm of the eye

The pupil is a virtual structure made up of the free space at the center of the iris. The iris comprises two groups of muscles: one composed of radial fibers (arranged like the spokes of a wheel), which widens the pupil; the other, with circular fibers, which narrows it. Their action modifies the diameter of the pupil and thus regulates the amount of light entering the eye, just as the diaphragm of a camera determines the aperture diameter of the lens.

The retina: photographic film

A lamellar structure a quarter of a millimeter thick, the retina is made up of 3 layers of neurons. The outermost layer contains photoreceptors containing light-sensitive pigment, which reacts to light with a chemical change that transforms light energy into electrical energy. This energy is then transmitted to the brain via ganglion cells in the innermost layer. The visual information is then regenerated by a complex process, requiring the help of other cells.