Astigmatism

If we often look at the phone, in most cases people hold the phone very low and most often look down and the lower rectus muscles of the eyes are constantly overstressed, and the upper rectus muscles of the eyes are constantly in a relaxed and stretched state.
Eye muscles are overstrained unevenly, the internal rectus muscles of the eyes and the lower rectus muscles of the eyes, and oblique muscles of the eyes that squeeze the eyeball to see at close range. But the external rectus muscles, which are located near the weight area, and the upper rectus muscles, which are responsible for the movement of the eyes upwards, are stretched and weak.
When one muscle of the eye is strong, and the other is stretched and weak and stronger one pulls the eyeball more than the other, refraction gets impaired, this phenomenon is called astigmatism and the picture begins to double.