What is the normal naked eye vision

Nowadays, more and more people wear glasses, and many primary school students wear myopia glasses. In fact, many people suffer from pseudomyopia, which can be cured through correction. However, parents do not understand naked eye vision and will make their children wear glasses when they hear their children say they can't see clearly. What is normal naked eye vision? How do I determine whether I am nearsighted and what methods can be used to correct my vision?

People often wonder why the visual acuity measured in different places is so different? One test showed 0.8, and another test showed 4.9, which is several times different. What's going on?

In fact, this so-called difference is because our country uses different vision recording methods at the same time. At present, there are two sets of vision recording methods commonly used in my country. One is the decimal recording method, which is based on the international standard vision chart. The other is the five-point recording method, which is an original recording method in my country and is based on the logarithmic vision chart. The fractional recording method is also often used abroad, which is similar to the decimal recording method we commonly use. In addition, there are some other vision charts in medical treatment, such as the LogMAR vision chart and the ETDRS vision chart, which are generally used in some special situations and will not be explained in detail here.

Today I will mainly compare the results of the decimal recording method and the five-point recording method, so that you can know the corresponding relationship after checking on different vision charts. The algorithms for the two recording methods are: V logarithm = 5 + lgV decimal. For example, 1.0 is recorded logarithmically as 5 + lg1 = 5.0. You can just remember the following table.

Of course, there are many eye charts that contain the results of both recording methods. Different medical institutions may choose one recording method based on their own habits.

What is vision? What are naked eye vision and corrected vision ?

Let’s first review the concept of vision. Visual acuity refers to how far away an object can be seen at a 1-point visual angle. Regardless of whether it is a fractional visual acuity chart, a decimal visual acuity chart, or a logarithmic visual acuity chart, they are all made based on this principle. Generally, the ability to see 1.0 (decimal visual acuity chart, i.e. 5.0 on the logarithmic visual acuity chart) at a 1-point visual angle is considered normal vision. Everyone's minimum visual threshold is different. It depends on the density of each person's retinal cone cells. When the density is higher, the visual threshold is higher and the minimum viewing angle is smaller. Therefore, there is a visual acuity of 3.0 (decimal visual acuity chart) or even higher.

When we talk about vision, we must also distinguish between naked eye vision and corrected vision. Naked eye vision refers to the vision measured directly without wearing glasses. Corrected vision refers to the vision you see after wearing glasses of appropriate power.

What is normal vision? What is considered abnormal vision?

Generally speaking, normal naked vision can reach 1.0, or 5.0.

People with refractive errors (myopia, hyperopia, astigmatism) will have lower than normal naked eye vision, but by wearing glasses, it can be corrected to normal vision 1.0 (5.0).

If your vision is still below normal even with glasses, you should have a comprehensive eye examination to see if you have other eye problems.

Therefore, if the naked eye vision is poor, but the corrected vision can reach 1.0, it is considered normal vision in medical terms. Abnormal vision is usually considered to be poor corrected vision, that is, even with glasses, the vision cannot reach 1.0.