Don’t confuse “vision” and “field of vision”

The ability of the eyes to distinguish the image of an object or recognize details within a certain distance is called vision. It is generally measured by the minimum distance between two points on an object that the eyes can distinguish. Physiologically, human vision is divided into two categories: far vision and near vision. As the name suggests, far vision mainly refers to the ability of the eyes to distinguish distant objects, while near vision refers to the ability of the eyes to recognize small targets nearby. The quality of a person's vision mainly depends on two factors: one is the function of the photoreceptor cells on the retina, and the other is the function of the eye's refractive system. If there is a problem in any of the above two factors, vision will deteriorate.

What about "visual field"? Visual field is also called peripheral vision. When one eye is fixed on a point in front of it, the spatial range that can be perceived by the peripheral vision of the eye is called visual field, which mainly reflects the visual function of the retina except the fovea.

Different people have different fields of vision, and even the same person's two eyes have different fields of vision. The size of the field of vision is affected by factors such as the bone structure of the face, the brightness of the object, and the color of the object.

Generally, people with big eyes and protruding eyeballs have a wider field of vision; people with smaller eyes have a relatively smaller field of vision. Due to the influence of the protruding nose bridge, the outer field of vision of the eye is larger than the inner field of vision; in addition, under the same brightness of light conditions, the field of vision measured with targets of different colors is also different. The white field of vision is the largest, followed by yellow and blue, then red, and the green field of vision is the smallest, mainly because the distribution range of photoreceptors of different colors in the retina is different. After knowing this, can you explain why traffic lights use red to indicate stop and green to indicate passage?

Source: Chongqing Industry-University-Research Cooperation Promotion Association

Author: Li Ge, Professor of Chongqing Medical University

Audit expert: Mao Yi

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