The lengthening of the eye axis in myopia is mainly due to the adjustment fatigue caused by the intensification of near eye use, which forms an adjustment lag and stimulates the backward growth of the eye axis. When the human eye looks into the distance, the focal point of the object falls on the retina and the vision is clearer. However, when looking at near objects, the focal point of the object often falls on the back of the retina first, and it is only through the adjustment of the lens that the focal point falls on the retina. However, some people may have adjustment lag, especially those with myopia. Adjustment lag means that the adjustment is not strong enough to make the focal point fall forward on the retina. This means that even after adjustment, the focal point falls behind the retina, and the retina perceives the position of the focal point as growing backwards, so the eye axis grows. This is the possible principle of myopic eye axis growth, and it is also the principle that is currently accepted.