What Is the Visual System?

One of the human sense organs. Consists of eyeballs, eye appendages, visual pathways, and the visual center of the occipital lobe of the brain

In humans, the visual system mainly includes the retina, optic nerve, optic cross, optic bundle, lateral geniculate body, optic radiation, and optic cortex (Figure 15-1). This special afferent system is perpendicular to the ascending sensory system and descending motor system of the cerebral hemisphere. The front part of this system is closely related to blood vessels and orbital bones. Therefore, visual path disorders have important value in neurological localization diagnosis. . This system consists of four visual meridians, the first neuron is the cone and rod cells of the retina; the second neuron is the bipolar cell in the retina; the third neuron is the ganglion cell in the retina; The four neurons are lateral geniculate bodies. These neurons are connected step by step, passing information to the visual center gradually. ^[1]

In some occasions or systems, the human visual system often becomes its end receiver. In this way, subjective evaluation of objective physical stimulation is required, and subjective evaluation is associated with psychological tests. The so-called psychological test or psychological measurement has a series of classifications and methods. The visual psychological test mostly uses the psychophysical method. Commonly used are: adjustment method, limit method, constant method, and have a certain evaluation scale.

Visual system mind constant

Visual psychological tests, like other psychological tests, include psychological constant tests. Common psychological constants are: threshold. The boundary between the sensible and the non-sensible stimuli (or poor stimuli) is called the stimulus threshold or discrimination threshold. Subjective and other values. In the one-by-one stimulus, when it is considered equal to a standard stimulus, the stimulus is said to be subjective and equivalent, and it is simply written as PSE. Limit. Feel the best or worst stimulus value. ^[2]

Vision is a feeling that people recognize the shape, light, and color characteristics of external objects. About 80% of the information people get from the outside world is obtained visually. With the increase of age, the visual organs gradually age, and the visual ability also gradually weakens.

Visual sensitivity reduces the eye's ability to sense external stimuli, called sensitivity. If the intensity of the external stimulus (light and shade and color) is small, it is high sensitivity; otherwise, it is low sensitivity. The sensitivity of the eyes to light and dark is manifested in the dark adaptation to light. The so-called dark adaptation refers to a person who has just entered a dark room from a bright place, and must gradually adapt to the dark environment to be able to see the surroundings. The so-called eye adaptation to bright light means that the eyes can quickly distinguish objects after being stimulated by strong light. Therefore, in order to avoid the consequences of poor dark adaptation, it is better for the elderly to have a medium-bright space as a transition from bright to dark; in order to prevent the unsuitability of bright light, some daily necessities should not be placed near At the windows, so as not to be easy to see and difficult to find. Eyes also show age differences in color sensitivity. The main reason is that the lens is cloudy, but it is also related to retinal aging. For example, older people often see colored objects as faded, with blue and green fading the most and red fading the least. Normal people are most sensitive to green during the day, and blue at dusk. If you observe two red and blue objects with the same brightness at daytime at dusk, you will feel that blue is more eye-catching than red (called the Park Jinye phenomenon). The elderly's susceptibility to red is also reduced at dusk due to the decline in their sensitivity to blue, which is the main reason why elderly people cannot see things clearly at dusk. Because of this, the elderly must pay attention to the layout and matching of colors in the indoor environment in daily life. For example, when red and green objects are approaching, the old person will see the two colors as overlapping, and the boundary becomes unstable and floating. When blue and green are close, the old person will see the two colors as faded or Mix with each other. If the green carpet is matched with the green wall, the elderly may not be able to distinguish and there is a danger of hitting the wall.

Visual system related concepts

Decreased basic visual function Visual function refers to the activity of completing certain visual tasks with the help of the eyes. It mainly includes the ability to distinguish small objects, also known as visual acuity or visual acuity; the ability to distinguish between distance and distance, also known as distance vision or depth vision. Visual acuity is medically called vision. The most common physiological cause of vision loss in the elderly is refractive inferiority to presbyopia; the pathological causes are cataract and glaucoma. Distance vision refers to the resolution of the eyes to the relative positions of objects in the visual space, also called deep vision. Judging the distance between objects can be based on the relative size of the objects, the occlusion relationship between the objects, and the relative speed of the objects. If the object is large, the distance is close; if the object is small, the distance is far; the blocked object is often judged to be behind the block; when the scene is clearly seen, the distance is close, and if it is blurred or fogged, the distance is far ; Fast moving objects look closer than slow moving objects. Of course, the adjustment of the eyes itself also plays a role in determining distance. According to the measurement of the vision of 164 men aged 30 to 70 years, it was found that the depth of vision was significantly reduced between the ages of 40 and 50, and the change was relatively small in the 10 years before and after. Due to the change in distance vision of the elderly, special care should be taken when going up or down the stairs to prevent falling or falling. ^[3]

Vision system elderly vision

Size or Shape Visual Size refers to the ability to recognize large and small objects. The ability of older people to recognize small objects decreases. According to some studies, although the sensibility of moving objects is higher than that of stationary objects, the sensibility of high-speed and low-speed movement is not different, and the sensibility decreases with age. The practical significance of this phenomenon is that under the condition of poor lighting conditions, the elderly are likely to treat a fast-moving motorcycle as a bicycle, coupled with the slow movement, it is prone to accidents when crossing the road. Shape vision: According to Oslo (1981), the elderly were tested using portrait detection and discrimination, and the results showed that elderly people need a large ratio (generally 3 times that of young people) to detect or discern.

In addition, the visual information processing speed and visual attention of the elderly have decreased significantly. Despite the above-mentioned changes in the vision of the elderly, due to long-term visual experience, in many cases can make up for the lack of visual ability. According to these rules of change, in order to adapt the elderly to the environment, two principles should be followed: make use of information from multiple senses such as hearing and smell to make up for their shortcomings; make the information of the sensation as simple and clear as possible, such as road signs, landmarks and common Medicine bottles, etc., can be added with different colors as signs or with different surface textures to facilitate touch and distinguish to facilitate the life of the elderly. ^[3]