Why is the E on the vision test form?

The eye chart is designed according to the principle of viewing angle. The so-called angle of view is the angle formed by the light emitted by two points in the outside world through the nodes in the eye. Under normal circumstances, the human eye can distinguish the minimum distance between two points to form a viewing angle as the smallest viewing angle, that is, a one-point viewing angle.

The eye chart is designed in units of one point of view. At present, the eye chart mainly checks the central vision, that is, to check the foveal visual acuity in the macular area of the retina, so that the preliminary situation of visual function can be understood simply and quickly, which is of great significance for the clinical diagnosis of eye diseases. The visual acuity is generally divided into two categories: distance vision and near vision, and the distance visual acuity is mostly based on the international standard eye chart, which is composed of 12 rows of "E" characters with different sizes and different opening directions; Measure from or from; Each line is marked, and the patient's line of sight should be parallel to the row, 5 meters away from the eye chart, and the distance between the eye chart and the person being examined must be correctly fixed, and the patient should be 5 meters away from the chart.

If the indoor distance is less than 5 meters long, a flat mirror should be placed at a distance of meters to reflect the eye chart. Cover one eye first, and identify the direction of the "E" notch from top to bottom with one eye until it is no longer recognizable, and then record it. Normal visual acuity should be above.

If the subject cannot see either, he or she should move forward until he or she can see, and his visual acuity is "distance 5=visual acuity"; If you can't see it within half a meter, you can make the test subject identify the index, measure the hand, light perception, etc. Visual acuity is recorded according to the examination. Near vision mostly uses the "J" near eye chart, the same method to identify the direction of the "E" word notch, until it can not be recognized, the near range can be adjusted by itself, normal near vision can see a line clearly at 30 cm, near vision examination is helpful for the diagnosis of refractive error.

Because eyesight measurement was invented by Western medicine, Western medicine was invented by foreigners, and most foreigners speak English, and they can recognize the letter e if they don't speak English, and the eye in English means eye, of course, you have to use e to measure the eye, right, hehe.

The "e" on the eye chart has a 1-point angle of view for each stroke, and the interval is also 1 point of view, thus forming a 5-point visual mark. is equivalent to 10 times the optoscope, and so on.

Trouble, thanks!

1. The "E" eye chart is designed according to the principle of perspective. The concept of an eye chart was first introduced in 1862, and it was originally a form of letters with similar stroke thicknesses, but it became difficult to popularize it, because it could not be used in areas where letters were not used and were illiterate. This was followed by the E-shaped eye chart and the C-shaped eye chart.

The C-shaped eye chart is known as the Landett ring eye chart. This kind of eye chart is common in Japan, and this kind of Randette ring eye chart, commonly known as the C chart, is also used in the recruitment of pilots in China.

2. The establishment of the E table in China is the "International Standard Vision Chart" drawn by Sun Jizhong in 1952. Later, in 1989, Guo Liangmin proposed improvements, and the "Standard Logarithmic Eye Chart" that we are now familiar with appeared. The Standard Logarithmic Eye Chart we now use is a form of three equally long letters e, each stroke or space of which is one-fifth of a square.

The letter E of this fence structure is useful for testing astigmatism. If you can clearly distinguish between left and right e, but it is difficult to recognize up and down e, then it is reasonable to suspect that you have a certain degree of astigmatism.

3. In fact, there are other eye charts that are not very well-known, such as the Chinese character eye chart in China. It is divided into a less-stroke version and a multi-stroke version. There is also an eye chart for babies and toddlers with animal silhouettes as elements.

There is also a special men's eye chart, and the women's eye chart is also very interesting.

An eye chart is a chart used to measure visual acuity. The eye chart is based on the principle of viewing angles. The eye charts used in the country are:

International standard eye chart, eye chart, logarithmic eye chart, Lamb ring eye chart. The eye chart is designed based on the principle of viewing angles. The so-called angle of view is the angle formed by the light emitted by two points in the outside world through the nodes in the eye.

Under normal circumstances, the human eye can distinguish the smallest angle of view formed by the minimum distance between two points, that is, the point of view. The eye chart is designed based on a single perspective. 【The development of the e-word chart in China】The reason why China uses the e-word chart is that in 19500, the Chinese Medical Association held the 9th General Assembly of the Chinese Medical Association, which recommended the "International Standard Vision Chart" drawn by Professor Sun Jizhong.

This table is based on the International Eye Chart's standards of 1-point viewing angle, 5-meter distance, and decimal recording. Finally, the "E" word mark was used for the entire table. In contrast, Professor Miao Tianrong and Professor Yu Heping proposed a 5-point logarithmic eye chart before his death.

After a long period of promotion, the number table has been widely used. However, a short spot in the middle of the e-optoscope is very short, which is easy to identify and guess, and the visual acuity is not accurate. In 1989, the logarithmic table was recognized as the national standard mock 11per31989.

In this version of the national standard, the improved E visual mark proposed by Guo Liangmin is adopted, which is the "E visual symbol of equal length with three strokes, and every stroke or gap is square." "This e is more in line with the meaning of strict viewing angle resolution design. Why is the "E" word used on the vision test form?

One of the benefits of the E-Form is that it has a certain grid structure, which helps to test astigmatism. For example, a person can clearly identify left and right E, but has difficulty identifying upper and lower E, so it is reasonable to suspect that he may have some degree of astigmatism. If you use a, f, y, etc., you can distinguish the direction of the tip even if you can't see it clearly.

If you use h, n, z, etc., there are only two left in the four directions, and the 50% accuracy rate is completely fine. If you use d, o, x, etc., what else can you test? So in fact, there are not many initials to choose from.

The neat and square shape on three sides is one of the great advantages of the e. However, e is not a one-of-a-kind option either. It is not impossible to test your vision with other letters, such as c, g, x.

Pilots use the C-table for visual acuity testing. Another example is Chinese watchmaking, which can completely change to Chinese characters without English and Chinese letters, so there are more options. It's just that the e-table is easy to use, and there is no need for this.

1. What we usually call visual acuity measurement is actually a test of the eye's ability to see far away (distance vision chart), which is accurately defined as: measuring the imaging on the smallest retina that can recognize its shape. There are many forms of eye charts, the most common being the E-line chart.

The E letter is used so that people who do not know the English alphabet can also understand the direction of the three horizontal line notches of the E word.

2. Our commonly used E-word international standard eye chart is designed according to the principle of viewing angle. The so-called angle of view is the angle formed by the light emitted by two points in the outside world through the nodes in the eye. At a distance of 5 meters, the projection of the top and bottom of the 10-line E on the retina is exactly 1 degree angle, and the calculation formula is:

Visual acuity = 1 degree angle.

3. The examination visual acuity is generally divided into two categories: distance vision and near vision, and the distance vision mostly adopts the international standard eye chart, which is composed of 12 lines of "E" characters with different sizes and different opening directions; Measure from to; Each line has a marker, the line of sight of the examinee should be parallel to the row, the distance between the eye chart and the examinee must be fixed correctly, the patient is 5 meters away from the table, if it is less than 5 meters, a plane mirror should be placed at the meter to reflect the eye chart.

4. Cover one eye when testing, and identify the direction of the "E" notch from top to bottom with one eye. If the test subject cannot see the page, move forward until he can see the position, and his visual acuity is "distance 5=visual acuity"; If you can't see it within half a meter, you can make the test subject identify the index, measure the hand, light perception, etc. Near vision mostly uses the Jaeger eye chart, and the same method is used to identify the direction of the E notch, and normal vision can be seen clearly at 30 cm.

A visual acuity test is done to determine the sensitivity of vision by looking at the clarity of the optoscope. Visual acuity, also known as visual acuity, refers to the ability of the eye to distinguish the smallest distance between two points of an object, that is, the ability of the eye to distinguish the tiny structure of an object. The visual acuity test chart has the smallest distance that the human eye can distinguish, that is, the last clear visual acuity of the angle, and the most commonly used is the national standard eye chart and the 5-point logarithmic eye chart, the distance between the eye chart and the subject must be properly fixed, and the distance between the subject and the surface of the eye chart is 5 meters.

If the room does not meet the requirements, the eye chart can be placed at the back of the candidate's seat.

A flat mirror is placed directly opposite the eye chart, and the field of view of the examinee is parallel to a row, and the eye chart reflected in the mirror is gazed. The visual acuity test must be checked in one eye, and during the examination, one eye is blocked with the spsame surface of the eye cricket, and the left eye is basically checked first, and then the right eye is checked. If you wear glasses, you should check your uncorrected visual acuity first, followed by glasses and correct your visual acuity.

The monocular eye can distinguish the vacant position of the "e" from top to bottom until it is no longer distinguishable. Normal visual acuity should be above. In the case of visual acuity testing, it is common to see this visual acuity test form composed of "E".

Not all eye charts in all countries are "e" eye charts. The process of eye chart in China: At the ninth exchange meeting of the Chinese Medical Doctor Association held in 1952, the Chinese Medical Doctor Association strongly recommended the "National Standard Vision Chart" produced by experts and professors Sun Jizhong.

This table is a de facto national standard, based on the international eye chart of 1 point angle, 5 meters apart, decimal records and other specifications, and finally the whole table was changed to Snellen's E-word visual mark. In China, the "E form" has been adopted, and the key factor is that the "E form" is suitable for groups who are unable to read the Latin alphabet of the article smoothly.

At the same time, it is applicable to groups in Chinese that do not use the initial list. The "e" visual element has a raster data structure that can detect shiny at a certain level. Naturally, we also have the Chinese character eye chart designed by Wenzhou Medical College, which has socialist democracy.

The English letter E conforms to the basic principle of visual effects, and it is convenient to distinguish the direction of the mouth, which is suitable for children and other groups who cannot read the Latin letters of the article smoothly. At the same time, the e-table also has the benefit of having a certain raster data construction, which is useful for detecting astigmatism.

It is designed according to the principle of viewing angle, at a distance of 5 meters, the projection of the top and bottom of the 10-line E on the retina is exactly one degree angle; This letter is designed to allow people who do not know the English alphabet to understand the direction of the three-horizontal line notch, which is universal and suitable for most people, and this design can also test the eyesight more accurately, which can minimize the error.

Because the design of this letter is more unique, first, it is easy to identify, second, there is only one side of the opening, third, it does not look complicated, fourth, it is relatively clear, and fifth, it looks good no matter which direction it looks like?