Abstract: vision is a very complex process. 80% of the brain’s feeling, understanding and memory of external objects depend on the visual system, and 85% of the knowledge in learning is also completed through the visual system.
what is “vision”?
visual acuity: also known as visual acuity, which is manifested in the ability to identify the target of fixation.
central vision: refers to the vision in the center of the macular fossa. At ordinary times, the visual acuity checked when entering school, joining the army and physical examination is the central visual acuity. Large visual acuity chart, when the inspection distance is 5m, the visual acuity is far vision, and the normal visual acuity is more than 1.0. Small visual acuity chart, the distance is 30 cm, the visual acuity checked is near visual acuity, and the normal visual acuity is also above 1.0.
peripheral vision: refers to the vision outside the retinal macula of the fundus, that is, the visual field, commonly known as “residual light”. In normal people, the upper monocular visual field is 60 degrees, the inner and lower monocular visual fields are 70 degrees, and the outer monocular visual field is 90 degrees. The inner part of human binocular visual field overlaps with each other, which is an important factor of stereo vision, while monocular people lack stereo vision.
corrected vision: the vision with glasses is corrected vision. Adults without other eye diseases but with corrected visual acuity less than 0.8 are amblyopic eyes. Amblyopia is divided into strabismus amblyopia, ametropic amblyopia, anisometropic amblyopia, form deprivation amblyopia and congenital amblyopia. The key to the treatment of amblyopia is to adhere to the three principles of
Visual acuity chart: it is a chart used to measure visual acuity, which is composed of multiple rows of large and small visual markers. Letters, numbers and graphics can be used as visual markers, and notch ring and E-shaped visual markers are multi-purpose. Snellen visual acuity chart, international standard visual acuity chart and logarithmic visual acuity chart are commonly used in the world.
low vision: in 1975, the World Health Organization stipulated that those with corrected vision below 0.05-0.3 and visual field > 10 degrees but < 15 degrees are called low vision. The number of patients with low vision is about three times that of the blind. Most of them can improve their vision to some extent with the help of a wide variety of visual aids.
blindness: the definition of blindness is not completely consistent in various countries. Generally speaking, corrected visual acuity below 0.05 is called blindness. There are about 30 million blind people in the world and about 4-5 million in China. Among the blind, there are occupational blindness, economic blindness, total blindness, monocular blindness, binocular blindness and so on.
visual acuity fluctuation: everyone’s visual acuity fluctuates and can change periodically within 24 hours. Most people’s best eyesight is around 9 a.m. and the worst eyesight is at dusk. How far is the vision of
? Standing on the ground, normal people can see trees and houses 1.6km away. In sunny weather, ships 10-25 kilometers away can be seen with naked eyes at sea level. The vision of people standing on the top of the mountain can be extended to 320 kilometers.
what is “vision”?
vision: it is the process of perception of objects when the human eye looks at objects. It is the ability of the human eye to understand, identify and process objects. If both eyes look at an object at the same time, the visual process perceived as a single object image is called binocular vision.
vision is a very complex process. 80% of the brain’s feeling, understanding and memory of external objects depend on the visual system, and 85% of the knowledge in learning is also completed through the visual system. Among the channels that transmit information to the brain, vision accounts for 65%. The visual system involves many eye functions, far exceeding the vision that allows us to see objects, such as how to move our eyes together, how to focus, how to judge the depth, how to perceive the surrounding situation, how to process, store and recall information, etc.
the main function of vision
1 Recognition function: analyze what the object is, how far away it is from us, and the shape and size of the object.
2. Storage function: store the information you see and restore it when necessary in the future.
3. Comparison function: compare the received information with the stored information.
4. Derive new things: analyze the newly received information and the originally stored information to derive new things.
binocular vision classification
binoculars can simultaneously perceive the shape, size, length, width, height, depth and diameter of external objects, as well as their own position, which is binocular vision. Binocular vision is divided into the following three levels:
1 Simultaneous vision: both eyes can perceive the external image at the same time.
2. Planar fusion image: the images of two eyes on the retina can be fused into one, but there is no sense of depth.
3. Stereo vision: it can produce the sense of diameter and depth of three-dimensional space.
vision is closely related to vision, but they are not the same thing. Many color blind people have very good vision. But when people’s eyesight decreases, it often affects their color discrimination. When serious eye diseases such as high myopia and optic nerve atrophy occur, visual impairment often occurs at the same time.