At arm's length.
According to sanitary standards, the optimal distance to the screen is 60–70 cm, while the minimum acceptable distance is 50 cm.
For monitors with a diagonal larger than 27 inches, it is recommended to increase this distance.
However, even when following these recommendations, the eyes can become tired and the cornea can dry out, as when working for long periods at a computer (as with any activity that requires visual strain, such as driving a car), a person blinks less frequently.
