Abstract: the visual acuity chart is formulated according to the principle of visual angle. Visual acuity is generally divided into far vision and near vision. At present, the visual acuity chart mainly checks the central visual acuity, that is, to check the visual acuity of the fovea of the macular region, so as to simply and quickly understand the preliminary situation of visual function, which is of great significance for the clinical diagnosis and treatment of eye diseases., The old standard logarithmic visual acuity chart was developed under the auspices of Professor Miao Tianrong, founder of Ophthalmology of Wenzhou Medical College. It was promulgated and implemented in 1990 and has been used for 22 years by 2012. The new national standard logarithmic visual acuity chart was implemented on May 1, 2012. The new standard is a mandatory standard, which is applicable to general physical examination of children, adolescents and adults aged 3 years and above, far and near visual acuity measurement and visual impairment screening of physical examination such as enrollment and recruitment, and ophthalmology and optometry clinic., It is understood that the standard visual acuity chart is divided into near visual acuity chart and far visual acuity chart. The measurement distance of near visual acuity chart is 25cm, which measures near visual acuity; The distance measured by the far vision chart is 5 meters, which measures the far vision. We are most familiar with and often contact the far vision chart., Compared with the original standard, The revised visual acuity chart consists of the original single visual mark in the first line (5 points recorded as 4.0) (E) Two visual indicators are added, which not only improves the measurement of low vision, but also reduces the probability of the first line of visual indicators being guessed correctly. Considering the current situation of the examination site, the size of the far vision chart and the original standard remain basically unchanged. The new standard also makes a large adjustment to the brightness standard of the light box, which will make the brightness clearer. New changes and significance: 1. Anti cheating : the standard visual acuity chart is divided into near visual acuity chart and far visual acuity chart. The measurement distance of near visual acuity chart is 25cm, which measures near visual acuity; The distance measured by the far vision chart is 5 meters, which measures the far vision. The most obvious change in the new version of the visual acuity chart is that the first line (5 points recorded as 4.0) is increased from the original single visual acuity mark (E) to two visual acuity marks, which can prevent inaccurate test results caused by fraud. 2. The size of the near visual acuity chart becomes larger: the whole size of the near visual acuity chart is close to a square (115 mm) × 105 mm), easy to carry; The number of visual markers in each row is changed to 5, and the brightness of the light box is improved, And according to the “crowding phenomenon” (the ratio of e word size to word spacing is 1:1) the principle design avoids the disadvantages of too few and uneven visual markers in each line, and makes the measurement of near vision more accurate and convenient. 3. Wide applications: the new visual acuity chart is a mandatory standard for national physical examination visual acuity test, which is suitable for general physical examination, enrollment, recruitment, etc. of children, adolescents and adults aged 3 years and over. Among them, near visual acuity chart is very important for measurement Try hyperopia, presbyopia and eye diseases more accurately., The old version of
standard logarithmic visual acuity chart was developed under the auspices of Professor Miao Tianrong, founder of Ophthalmology of Wenzhou Medical College. It was promulgated and implemented in 1990 and has been used for 22 years by 2012. The new national standard logarithmic visual acuity chart was implemented on May 1, 2012. The new standard is a mandatory standard, which is applicable to the general physical examination of children, adolescents and adults aged 3 and above, the measurement of far and near vision and the screening of visual impairment in physical examination such as enrollment and recruitment, and the clinical aspects of Ophthalmology and optometry.
it is understood that the standard visual acuity chart is divided into near visual acuity chart and far visual acuity chart. The measurement distance of near visual acuity chart is 25cm, which measures near visual acuity; The distance measured by the far vision chart is 5 meters, which measures the far vision. The far vision chart we are most familiar with and often contact is the far vision chart.
compared with the original standard, The revised visual acuity chart consists of the original single visual mark in the first line (5 points recorded as 4.0) (E) Two visual indicators are added, which not only improves the measurement of low vision, but also reduces the probability of the first line of visual indicators being guessed correctly. Considering the current situation of the examination site, the size of the far vision chart and the original standard remain basically unchanged. The new standard also makes a large adjustment to the brightness standard of the light box, so that the brightness will be clearer.
New changes and significance:
1. Anti cheating: the standard visual acuity chart is divided into near visual acuity chart and far visual acuity chart. The measuring distance of the near visual acuity chart is 25 cm, and the near visual acuity is measured; The distance measured by the far vision chart is 5 meters, which measures the far vision. The most obvious change in the new version of the visual acuity chart is that the first line (5 points recorded as 4.0) is increased from the original single visual acuity (E) to two visual acuity markers, which can prevent the inaccurate test results caused by fraud.
2. The size of the near visual acuity chart becomes larger: the whole size of the near visual acuity chart is close to a square (115mm) × 105 mm), easy to carry; The number of visual markers in each row is changed to 5, and the brightness of the light box is improved, It is designed according to the principle of “crowding phenomenon” (the ratio of e word size to word spacing is 1:1), which avoids the disadvantages of too few and uneven visual markers in each line, and makes the measurement of near vision more accurate and convenient.
3. Wide application: the new visual acuity chart is a mandatory standard for national physical examination visual acuity test. It is suitable for general physical examination, enrollment and recruitment of children, adolescents and adults aged 3 and above. Among them, the near vision chart is more accurate for testing hyperopia, presbyopia and eye diseases. The reservation and function of
and
are:
,
1, and five gold standards: the visual angle, visual form, standard distance, visual standard increase rate and eyesight record. The five gold standard still keeps the five gold standard in the original national standard, so as to maintain the scientific and advanced standard of the original standard.
2. Keep the five point recording method: the current visual acuity chart adopts the five point recording value, that is, the visual acuity is divided into five levels, marked as e or C, with a total of 14 lines, including 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1 and 5.2, of which less than 5.0 means abnormal. Logarithm is a function of conversion, in which the size of the visual target represents the angle with the angle of view. This method is to logarithmically process the angle. For example, the function conversion of relative decimals: quintile logarithmic vision = 5 + LG (decimal vision). That is, 2.0:5.3, 1.5:5.2, 1.2:5.1, 1.0:5.0, 0.5:4.7, 0.2:4.3, 0.1:4.0. This recording method conforms to the physiological and physical laws of human eyes, can properly solve the defects of other recording methods, and can directly carry out scientific vision statistics. How can
and
correctly use the new vision chart?
tip: distance line of sight formula
according to relevant media reports, at presentThe new paper standard visual acuity chart has been published by people’s Health Publishing House, the light box of visual acuity chart has been produced by manufacturers, and the standard text has been published by China standards publishing house. In the future, the vision chart that has been used for many years will be gradually replaced with a new standard version. So, when the new vision chart really comes around, how should parents teach their children to use the new vision chart?
and
use the visual acuity chart to measure the visual acuity indoors. The tested person should be 5 meters away from the visual acuity chart. If the indoor distance is less than 5 meters, the parents can place a flat mirror at a place of 2.5 meters to reflect the visual acuity chart, and the measurement is from 0.1 to 1.5, or 4.0 to 5.2. Because each line of the visual acuity chart has a label, the line of sight of the tested person should be parallel to 1.0, During the inspection, point to the sight mark from top to bottom, answer correctly, and then point to the next line. The recognition speed shall be controlled within 3-5 seconds each time. The normal visual acuity is above 1.0. If the subject cannot see clearly, he must move forward until he sees it. The formula can be used to calculate: visual acuity = (0.1 × Distance) / 5.
and
are tested with a near vision chart, and the test distance can be adjusted by the tester. Taking 30cm as the benchmark, the line of 1.0-4.0 can be seen as normal, which is more scientific, accurate and convenient.
it should be added that the visual acuity chart should be placed in a place with sufficient light or illuminated by fluorescent tubes.
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