There is not only one kind of eye chart, but also many kinds, including international version and standard version. General hospitals will use these two kinds of eye charts for vision test, but which one is uncertain, it depends on the situation.
The eye chart is designed according to the principle of visual angle. The so-called viewing angle is the angle formed by the light emitted by two external points passing through the nodes in the eyes (that is, the angle formed by the intersection of two external objects when they enter the eyes). In general, the human eye can distinguish the smallest distance between two points to form the smallest angle of view, that is, the tiny angle of view. The eye chart aims to effectively detect vision in a unit of one-minute viewing angle.
Extended data:
Precautions:
1, the eye chart should be in a well-lit or well-lit place.
2. The line10, i.e. 1.0, should be at the same level as the examined eye.
3. Check the right eye first, then the left eye.
4. If you wear glasses, you should also check your vision with glasses, which is also called corrected vision. During the inspection, the eye patch should cover the non-inspection eyes tightly, otherwise the visual acuity measured by both eyes will be higher than that of the single eye, which will affect the accuracy of the inspection results and even cause? Diagnosis, delay of illness.
In addition, squinting, tilting your head or moving your body are all incorrect postures, which will also make the inspection results not objective, so you must pay attention when checking.
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