What is Considered Normal Human Vision?

Normal human vision is equivalent to 1.0 on a decimal vision chart or 5.0 on a logarithmic vision chart. Vision refers to the ability to see objects clearly at a certain distance under the premise of a 1-minute angle of view. Both the fraction vision chart, the decimal vision chart, and the logarithmic vision chart are created based on this principle. Generally, the ability to see clearly at 1.0 (decimal vision chart, equivalent to 5.0 on the logarithmic vision chart) under a 1-minute angle of view is considered normal vision.

Everyone's minimum visual threshold is different, depending on the density of cone cells in their retina. When the density is higher, the visual threshold is higher, and the minimum angle of view is smaller. Therefore, there can be a vision of 3.0 (decimal vision chart) or even higher. Vision is not equivalent to refractive power.

The standard for normal vision also includes the following content:

1. Central vision refers to the vision determined by people usually checking the vision chart, including distance vision (viewing the vision chart from more than 5 meters away) and near vision (viewing the vision chart from 30 centimeters away). Farsighted patients tend to have better distance vision than near vision, while nearsighted patients have the opposite. Patients with astigmatism may have poor distance and near vision. Central vision is considered normal only when both distance and near vision reach 0.9 or above.

2. Peripheral vision refers to the range of vision visible outside the area of fixation when the eyes are focused on a particular target. This is also commonly known as "peripheral vision" or "side vision". Generally speaking, the range of peripheral vision for normal individuals is quite large, reaching 90 degrees on both sides, 60 degrees above, and 75 degrees below. Patients with myopia or night blindness may have poorer peripheral vision, and some eye diseases can also lead to loss of peripheral vision.