The increasing rate of the target is the number of mixed sets, and the foreground is a arithmetic progression (0. 1 ~ 1.0), which is recorded in decimals. The above-mentioned 5.0 is represented by logarithmic visual acuity chart, also called 5-point logarithmic visual acuity chart. It divides vision into five grades, and the vision standard is e or c, *** 14 line. Logarithmic distance visual acuity chart is that the line of 1 1 can be distinguished at a distance of 5 meters, which is regarded as standard visual acuity and recorded as 5.0.
Extended data:
Many people think that it is normal as long as the vision can reach 1.0 or above. In fact, the vision of 1.0 only shows that some people's vision is normal. Strictly speaking, the standard of normal vision also includes the following:
1. central vision: that is, the vision determined by people looking at the eye chart at ordinary times, including far vision (looking at the eye chart at a distance of 5 meters) and near vision (looking at the eye chart at a distance of 30 centimeters). The performance of hyperopia patients is that hyperopia is better than myopia; Myopia patients are the opposite. Astigmatism patients have poor farsightedness and myopia. When the near and far vision reaches above 0.9, it can be said that the central vision is normal.
2. Peripheral vision: When the eyes look at a certain target, whether the visual range of the non-gaze area is large or small is called peripheral vision, which is often called "canthus". Generally speaking, the peripheral visual range of normal people is quite large, reaching 90 degrees on both sides, 60 degrees above and 75 degrees below. Peripheral vision of patients with myopia and night blindness is poor, and some fundus diseases can also cause peripheral vision decline.
3. Stereo vision: Stereo vision is the highest kind of vision, that is, on the basis of normal vision in the center of both eyes, the distance relationship between objects in space can be felt through the harmony of the two hemispheres of the brain. Some people have normal central vision, but abnormal stereoscopic vision, which is called stereoscopic blindness in medicine.
Although we usually only check the central vision, in medicine, only the central vision, peripheral vision and stereoscopic vision meet the physiological requirements can be regarded as normal vision.
Baidu encyclopedia-vision
Baidu encyclopedia-logarithmic visual acuity chart