The SPH indicates the amount of lens power, measured in dioptres, that you need to achieve best vision. If the number has a minus (-) sign, you are short-sighted where you generally struggle to see objects in the distance. If the number has a plus sign (+), you are long-sighted where you generally struggle to see clearly up close. If your sphere says plano, PL, 0.00, ∞, you have a zero spherical power where you are neither long nor short-sighted.