When we sit in a chair, our hips should be as far back in the chair as possible. Head, spinal column, shoulders and hips should be in straight line and erect. Legs should touch the ground and not in hanging position. Things should be in horizontal position. While we read, the book should be on table but the book should not be too far away or near the eyes. The approximate distance between book and eyes should be at least 30 cm. If we do not follow this rule, eyesight problem may occur.