Why is the E test used for vision? Why is the test visual acuity indicated by E?

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 use the "J" near vision 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 people with refractive error.

Why is the "E" on the vision test form? The E-shaped eye chart has only 4 directions, and the probability is 25%, while the C-word eye chart has 8 opening directions, and the probability is reduced to. And in optometry.

Because the patient has oblique astigmatism, the C-shaped eye chart is used because the E-chart cannot be used to determine the horizontal and vertical openings when using the E-chart after astigmatism is removed

Our commonly used "E" eye chart is designed based on the principle of perspective.

What we usually call visual acuity measurement is actually a test of the eye's ability to see far away, which is accurately defined as measuring the imaging on the smallest retina that can recognize its shape.

Why do you use the letter "e" in the eye chart, there is a very professional concept involved here - the principle of vision. The so-called angle of view, that is, under normal circumstances, the human eye can distinguish the minimum distance between two points to form the angle of view is the smallest angle of view, that is, a point of view.

At a distance of 5 meters, the 10 lines of "E" are two horizontal lines above and below, and the projection on the retina is exactly one point of view. Compared with the familiar three-stroke equal-length "e" character, each stroke or space is one-fifth of a square, this "e" character is more in line with the strict perspective resolution design meaning.

The eye chart is designed in units of one point of view. If you are 5 meters away from the myopia table, the smaller the orange withered characters that can be seen clearly, the smaller the angle of view formed between the words and the eyes.

Each stroke and gap of the three-stroke equal-length letter E is one-fifth of the square, and it has a certain grid structure, which is very helpful for testing astigmatism, so E is most in line with the design significance of strict viewing angle resolution.

To put it simply, we choose the word e because its shape, size, arrangement, etc. are more in line with the "correct resolution" of our eyes, and this design can relatively reflect your real vision condition.

The so-called angle of view, under normal circumstances, the human eye can distinguish the minimum distance between two points to form the angle of view is the smallest angle of view, that is, a point of view. At a distance of 5 meters, the 10 lines of "E" are two horizontal, and the projection of Wang Bei on the retina is exactly one point of view. The eye chart is designed in units of one point of view.

If you are 5 meters away from the myopia table, the smaller the characters that can be seen clearly, the smaller the angle of view between the expression and the eye. Each stroke and gap of the three-stroke equal-length letter E is one-fifth of a square and has a certain grid structure, which is very helpful for testing astigmatism. Therefore, e is most in line with the strict viewing angle resolution design meaning.

To put it simply, we choose the word e because its shape, size, arrangement, etc. are more in line with the "resolution" of our eyes, and this design can relatively reflect your real vision. The measurement of visual acuity is to check the ability of the eye to see the distance, and the reason why the letter E is used on the eye chart is determined by the principle of the high angle of the Lingzhou. Visual acuity is expressed by a formula that is v=1 a, where a represents the viewing angle.

Usually the eye can distinguish the angle of view generated by the minimum distance between two points, which is called the minimum angle of view. There are 10 lines of E on an eye chart, and the projection of the upper and lower sides on the retina is exactly the smallest viewing angle. e three horizontal equal length, each stroke or gap is a square of 1 5, relatively in line with the perspective resolution design.

Acute loss of vision due to trauma to the eye, blurred vision, red and swollen eyes, and foreign bodies in the eyes. Generally, mild wear can heal in about a week; In severe cases, antibiotic eye drops should be used under the guidance of a doctor to prevent infection; Steroid eye drops can reduce inflammation and prevent scarring, which can lead to irreversible vision loss. Some medications, especially antidepressants, blood pressure lowering drugs and antihistamines, can slow down tear production or change the composition of tears, causing tears to evaporate quickly.

However, there is no need to worry, it will gradually improve after stopping the drug, and if the eye discomfort is severe, you need to adjust the dosage or change other drugs by a professional doctor.

This e in the eye chart is not called "e", it is called optoscope. The size of this optographic target is very particular about the size and arrangement. The entire eye chart has a total of 14 rows, and each letter is designed according to the method of grid number, with a height of 5 units and a width of 4-6 units.

The reason why most of the eye charts in China use the letter E is probably because E has a certain grid structure, which is helpful for testing astigmatism. Legal basis, Article 1 of the "Notice on Strengthening the Protection of Students' Vision and Comprehensively Carrying Out School Health Care Work" regards the protection of students' eyesight and the prevention and treatment of students' myopia as the primary task of the current school health care work.

It is necessary to continue to implement the spirit of the "Joint Circular on Implementing the Implementation Measures for the Protection of Students' Vision (for Trial Implementation)" issued by the former Ministry of Education, the Ministry of Health, and other ten units, and take practical measures in light of the actual conditions in various localities to reduce the burden of students' homework, carry out physical activities, pay attention to eye hygiene, and improve the conditions for lighting and lighting, so that the work of protecting students' eyesight can achieve practical results as soon as possible.

Leaders of education departments at all levels, schools of all types at all levels, and all educators should attach importance to the protection of students' eyesight and regard it as an important task for comprehensively implementing the education policy and cultivating qualified personnel. School leaders, subject teachers and class teachers should establish a post responsibility system, and Nahui should perform their duties and fulfill their responsibilities. Higher education departments should conduct regular inspections and put schools to protect students' eyesight and physical education.

The achievements of health work are one of the important criteria for evaluating the quality of school education.

Health departments at all levels should coordinate with local education departments to urge all types of schools to do a good job of protecting students' eyesight.

With the excessive use of eyes in today's life, many people wear glasses to help themselves see everything in the world clearly, but every time the prescription deepens, they have to return the glasses again, so how is the "E sheet" used to check our eyesight formulated?

In daily life, whether it is a college student or a primary school student, it will be myopia because of improper sitting posture or excessive use of eyes for a long time, myopia is also called short-sightedness, because this kind of eye can only see near and not far, when myopia first occurs, it is necessary to diagnose whether it is true or false myopia.

I think it's because there are obvious differences in the four directions of the word, which makes it easy to distinguish.

It's designed according to the principle of perspective, and it's expressed in a formula that v=1 a means visual acuity and a is the viewing angle.