Vision refers to the ability of retina to distinguish images. Visual acuity is judged by the ability of retina to distinguish images. However, when the refractive medium of the eye (such as cornea, lens, vitreous body, etc.). ) become turbid or have refractive errors (including myopia, hyperopia, astigmatism, etc.). ), the visual acuity of eyes with good retinal function will still decline.
Opacity of refractive medium can be treated by surgery, and ametropia needs to be corrected by lens. The biggest feature of human eyes is the ability to recognize details, which is often expressed by the resolution of viewing angle, called vision.
The standard of expressing vision is the opening angle of the smallest character that human eyes can recognize. The visual acuity of normal eyes is above 1.0, which usually refers to the minimum separable visual acuity of eyes rather than the minimum visible visual acuity. Therefore, the eye chart reflects the minimum visual angle separated by the two points of the subject's gaze, that is, the minimum separable vision, or 65,438+0' visual angle vision, which can represent the subject's best visual function.
Vision refers to the ability to distinguish tiny or distant objects from tiny parts. The ability of eyes to identify distant objects or targets is called hyperopia, and the ability to identify nearby tiny objects or targets is called myopia. In the health examination, it is mainly to check hyperopia.
Under certain conditions, the smaller the object that the eyes can distinguish, the greater the visual acuity. The basic feature of vision is to distinguish the distance between two points. Vision can be divided into static vision, dynamic visual acuity vision and night vision.
Static vision refers to the vision that both people and observed objects are detected in a static state, and dynamic visual acuity refers to the ability of eyes to capture images, decompose and perceive moving target images when observing moving targets. Driving in high-speed environment will also change the physiological state of human body, which is embodied in: the dynamic visual acuity of eyes is reduced.