1, with different definitions: In-focus refers to the position where the object is imaged on the retina of the eye when the eye is far away, and out-of-focus refers to the position where the object is imaged in front of the retina of the eye when the eye is near.

2. Different visual comfort: When the eyes are focused, the visual comfort is relatively high, and the eyes can look at distant objects more relaxed, while when they are not focused, the visual fatigue is relatively strong, which will cause discomfort symptoms such as visual fatigue and dry eyes.