Vision - a physiological process, which allows to get information about the size, shape and color of objects, their relative position and distance between them. Vision is possible only under normal functioning of the visual analyzer in General. According to the teaching of I. P. Pavlov, visual analyzer includes peripheral paired organ of vision - eye with his perceiving light photoreceptors - rods and cones of the retina (Fig.), the optic nerves and visual pathways, subcortical and cortical visual centers. Normal stimulus of the organ of vision is light. Rods and cones of the retina perceive light waves and transform their energy into buzz, which through the optic nerve is transferred by conduction paths in the visual center of the brain, where there is a visual sense.

Coli (right) and cone (left) net shell

Under the influence of light in rods and cones is the collapse of visual pigments (rhodopsin and iodopsin). Sticks are functioning in the light of weak intensity, in the twilight; visual experience obtained colorless. Cones operate during the day and in bright light; their function determines the sense of color. In the transition from daylight to twilight moves maximum light sensitivity in the spectrum towards his shortwave and items in red (Mac) appear black, blue (cornflower) - very light (the phenomenon of Purkinje).
Visual analyzer person under normal conditions, provides binocular vision, i.e. the vision with two eyes with the unified visual perception. The primary reflex mechanism of binocular vision retina, is merging reflex image - fusion reflex (diffusion)arising while irritation functionally different neural elements of the retina of both eyes. Consequently there are physiological vision subjects that are closer to or further fixed point. Physiological vision helps to estimate the distance of the subject from the eye and creates a feeling of relief, or stereoskopičnosti, vision.
At the sight of one eye (monocular vision) stereoscopic vision impossible and depth perception is mainly due to secondary subsidiary signs distance (visible value of the subject, linear and air perspective, the block of some other items, accommodation of the eye, and so on).
In order for visual function was carried out for a sufficiently long period of time without fatigue, it is necessary to observe a number of hygienic conditions to facilitate vision. These conditions are combined in the concept of "hygiene of view". These include: good uniform illumination of natural or artificial light workplace, limitation of blizkosti, sharp shadows, the correct position of the body and the head during operation (without a strong inclination on the book), a sufficient distance of the subject from the eyes (30-35 cm), a small breaks every 40-45 minutes work.
The best lighting is natural daylight. It should avoid lighting eye direct sunlight, as they have a glare. Artificial lighting is created using lamps with conventional electric or fluorescent lamps. For Troubleshooting and limitations glare of lights and reflective surfaces height of hanging lamps shall not be less than 2.8 m from the floor. Especially important good lighting in classrooms schools. Artificial illumination on the desks and cool the boards shall be not less than 150 Lux [Lux (LX) - the unit of illuminance] under tungsten lighting and no less than 300 Lux with fluorescent light. You must create adequate illumination of a workplace and at home: a day to work at the window, and in the evening with a lamp in 60 VT, covered with shade. The lamp is put to the left of the subject. Children with myopia (see) and hyperopia (see) to the appointment of the relevant points.
Basic visual functions and methods of their study are described in the relevant articles (see Adaptation of the eye, the visual Acuity, visual Field, Perimetry, the colour sensation).
Various diseases of the eye, optic nerve and Central nervous system lead to a decrease in vision and even blindness (see). The vision is affected: violation of transparency of the cornea, lens, vitreous body, pathological changes in the retina, especially in the macula, inflammatory and atrophic processes in the optic nerve, brain disease. In some cases, the reduction is connected with diseases of the eye. These include: cataract caused by the systematic influence of radiant energy considerable intensity (x-rays, infrared rays); progressive myopia in conditions of direct voltage of view with fine small business; conjunctivitis and keratoconjunctivitis in persons in contact with hydrogen sulphide and dimethylsulfate. To prevent these diseases is of great importance to the observance of the rules of public and personal protection eyes from harmful factors. (See also the Eye).