Hello everyone, thank you for the invitation. Today I would like to share with you the problem of vision conversion and some confusion with the conversion of vision tables. If you don’t understand it yet, it doesn’t matter. , because I will share it with you next, I hope it can help you and solve your problems, let’s get started!
Table of contents
- How big is the word 48 on the eye chart
- How many meters is 0.4 visual acuity
- 750 degree visual acuity chart conversion
- Visual acuity table conversion
- Corresponding values of two visual acuity standards
- Lens conversion formula
1. Vision How big is the word in table 48?
Visibility 48 generally refers to 4.8 on the vision chart. There is no very accurate conversion formula between visual acuity and myopia. It is generally considered that visual acuity 4.8 is generally 150 degrees myopia.
2. How many meters is 0.4 visual acuity
The visual acuity chart is based on It is designed based on the principle of viewing angle. When the subject is 5 meters away from the eye chart, the visual acuity of 1.0 and above is generally considered normal. If the visual acuity level is relatively low, this situation cannot be recognized, so the visual acuity is Not very good.
For example, some people measure 0.4, which is abnormal vision. If you look at it from the vision conversion table, the corresponding The degree is 250 degrees.
3. 750-degree eye chart conversion
International 1-point system The correspondence between the decimal myopia visual acuity chart and the Chinese 5.0 logarithmic visual acuity chart is as follows: 5.2 is equivalent to 1.5, 5.1 is equivalent to 1.2, 5.0 is equivalent to 1.0, 4.9 is equivalent to 0.8, 4.8 is equivalent to 0.6, 4.7 is equivalent to 0.5, 4.6 is equivalent to 0.4 , 4.5 is equivalent to 0.3.
Conversion formula for myopia degree: D=1/F. If myopia degree is 0.5, the degree of glasses should be 1/0.5=200 degrees.
4. Vision chart conversion
How to use the vision chart to convert myopia: D=1/F, D is the diopter, F is the The naked eye visual acuity found on the eye chart. For example: the naked eye visual acuity is 0.5, and the myopia degree of the eye converted by the formula is 0.2. The degree of myopia is approximately 5.00D. This conversion method is only a rough estimate and is inaccurate. To obtain the true degree of myopia, the result should be more accurate.
It is recommended that before wearing glasses, you must undergo an optometry examination to check the degree before wearing glasses.
5. Corresponding values of two standards of visual acuity
International standard near visual acuity chart (decimal recorded values) and standard logarithmic near visual acuity chart (five points) The conversion of recorded values) is as shown in the following table: Decimal recorded value 0.10.120.150.20.250.30.40.50.60.81.01.21.5 Five-point recorded value 4.04.14.24.34.44.54.64.74.84.95.05 .15.2
6. Lens conversion formula
1 diopter is defined The light passes through the lens and forms a focus one meter behind the lens. Expressed as D, f represents the focal length and the formula is D=1/f. If the focal length of the lens is 0.5 meters, the diopter of the lens is 1/0.5=2. It is customary. People like to call this 200 degrees.
Generally speaking, people with refractive errors have poor vision. The higher the refractive power, the worse the naked eye vision. Low. But this is not absolute. Some people have low refraction, but their visual acuity is very low, because refraction is not the only factor that affects the quality of vision
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