A plus sign indicates that the designated eye is farsighted, while a minus sign indicates that the designated eye is nearsighted. This is measured in diopters, the unit of measurement that indicates the nearsightedness or farsightedness of the eye. Diopters are normally abbreviated to a simple D, so an OD -1.25 indicates that a patient is one and one quarter of a diopter farsighted in their right eye. source :http://www.glassescrafter.com/information/what-eyeglasses-prescription-means.html
Sphere indicates the amount of lens power, measured in diopters (D), prescribed to correct nearsightedness or farsightedness. If the number appearing under this heading has a minus sign (-), you are nearsighted; if the number has a plus sign (+) or is not preceded by a plus sign or a minus sign, you are farsighted.