The visual analyzer plays an essential role in the perception of the surrounding world. More than 90% of information we receive with the help of sight.
The visual analyzer consists of three parts. The peripheral part is represented by the eyes, the conductive part – by the optic nerves, the central part – by the visual zone of the cerebral cortex. With the participation of all three elements, light stimuli are perceived and analyzed, and we see the world around us.
The peripheral part of the visual analyzer is represented by the organ of vision.
The eyeball is protected from external influences by an auxiliary apparatus. The eyeball is protected from mechanical damage by the walls of the skull orbit, in which it is located. Protects eyelids and eyelashes from dust and moisture. The lacrimal glands secrete a tear that washes away dust and moisturizes the surface.
Attached to the eyeball are muscles that enable it to move.
In the eyeball, three membranes are distinguished: outer, vascular and reticular.
The outer (white) membrane in the front part is represented by a transparent convex cornea, and in the back part – an opaque white sclera.
The choroid supplies the eye with blood. In front of it there is an iris. The cells of the iris contain the pigment melanin, the amount of which determines its color. The pupil is located in the central part of the iris. The pupil can expand and contract depending on the brightness of the light.
Behind the pupil is the lens – a biconvex transparent lens. The lens can change its curvature and focus light rays on the inner shell of the eye. This process is called accommodation.
Between the cornea and the iris is the anterior chamber, between the iris and the lens is the posterior chamber. They contain a liquid that supplies the cornea and lens with nutrients.
The space behind the lens is filled with the vitreous humor.
The inner lining of the eye – the retina – contains light-sensitive cells (photoreceptors), represented by rods and cones.
The rods provide twilight vision. Cones respond to bright light and provide color vision. The retina contains three types of cones: some perceive red, others green, and others blue. As a result of the interaction of all three types of cones, we see different colors.
Most of the cones are located in the middle of the retina and form the so-called macula. The exit site of the optic nerve from the retina does not contain photoreceptors and is called a blind spot.