I suspect that resting your chin on the weight of your arm like this....
May be implicated in double vision/lazy eye. I don't know how yet. I am going to research further. My suspicions are a shortening of the face or something pinched. It is especially bad if on knees leaning forward with more body weight. There is more weight/pressure while laying on stomache and looking up. Additionally, our society looks at screens all day = not great for eyes.