Офтальмология

SIGHT - the physiological process, allowing to receive representation about size, the form and color of subjects, their relative positioning and distance between them. 3. it is possible only at normal functioning the visual analyzer as a whole. According to I.P.Pavlova's doctrine, the visual analyzer includes peripheral pair body of 3.-eyes with his{its} photoreceptors perceiving light - sticks and колбочками retinas (rice)., optic nerves, visual ways, subcrustal and корковые the visual centers. раздражителем body 3. light is normal. Sticks and колбочки retinas of an eye perceive light fluctuations and transform their energy into nervous excitation, a cut through an optic nerve is transferred on conducting ways to the visual center of a brain where there is a visual sensation. Подробнее...

Under influence of light in sticks and колбочках there is a disintegration of visual pigments (родопсина and йодопсина). Sticks function at light of weak intensity, in twilight; the visual sensations received at it, are colorless. Колбочки function in the afternoon and at япком illumination: their function defines{determines} sensation of chromaticity. At transition from day time illumination to twilight there is a moving a maximum of light sensitivity a spectrum in the direction of his{its} short-wave part and subjects of red color (poppy) seem black, dark blue (cornflower) - very light (phenomenon Пуркинье). Подробнее...

The visual analyzer of the person in normal conditions provides binocular sight, i.e. sight with two eyes with uniform visual perception{recognition}. The basic reflex mechanism of binocular sight is the reflex of merge of the image - фузионный a reflex (фузия), arising at simultaneous irritation of functionally unequal nervous elements of a retina of both eyes. Thereof there is a physiological doubling the subjects which are taking place closely or further fixed point. Physiological doubling helps to estimate remoteness of a subject from eyes and creates sensation рельефности, илп stereoscopy, sight. Подробнее...

At 3. one eye (монокулярное sight) stereoscopy 3. is impossible also the perception{recognition} of depth is carried out гл. обр. Due to secondary auxiliary attributes of remoteness (the seen size of a subject, linear and air prospects, загораживание one subjects others, accommodation of an eye, etc.). Подробнее...

That visual function was carried out during enough long time without exhaustion, it is necessary to observe a number{line} of the hygienic conditions facilitating 3. These conditions are united in concept of "hygiene - sight". To them concern: good uniform illumination by natural or artificial light of a workplace, restriction блескостп, sharp shadows, correct position of a trunk and a head in an operating time (without a strong inclination above the book), sufficient removal{distance} of a subject from eyes (on the average 30-35 sm), small breaks every 40-45 minutes works. Подробнее...

The best illumination considers a natural daylight. Thus it is necessary to avoid illumination of eyes by direct solar beams, т. To. They have blinding an effect. Artificial illumination is created by means of fixtures with usual electric or luminescent lamps. For elimination and restriction of blinding action of light sources and reflecting surfaces the height подвеса fixtures should be not less than 2.8 m from a floor. Especially important good illumination in educational classes of schools. Artificial light exposure on school desks and blackboards should make not less than 150 лк [lux {лк} - unit of light exposure] at illumination by lamps накаливания and not less than 300 лк at luminescent illumination. It is necessary to create sufficient light exposure of a workplace and in domestic conditions: it is necessary to work for a window, and in the evening with a desk lamp 60 вт, covered with a lamp shade in the afternoon. A lamp put to the left of a subject of work. With short-sightedness and a far-sightedness purpose{assignment} of corresponding glasses is necessary for children. Подробнее...

Various diseases of an eye, optic nerve and ц. н. With. Result in downturn 3. and even to blindness. On 3. influence: infringement of a transparency of a cornea, a crystalline lens, стекловидного bodies, pathological changes of a retina, is especial in the field of a yellow stain, inflammatory and атрофические processes in an optic nerve, diseases of a brain. In нек-рых cases downturn 3. is connected to occupational diseases of eyes. To them concern: the cataracts caused by regular influence of radiant energy of significant intensity (X-rays, infra-red beams); progressing short-sightedness in conditions of a constant pressure{voltage} of sight at exact fine work; конъюнктивиты and кератоконъюнктивиты at the persons adjoining with hydrogen sulphide and диметилсульфатом. For the prevention{warning} of these diseases the great value has observance of rules public and an individual defence of eyes from harmful factors. Подробнее...