Sphere – Written as SPH often, this is the lens power required and prescribed to correct either long-sightedness or nearsightedness. It is measured in the unit known as diopters (D). You know you are nearsighted if the number that is listed for the Sphere heading in the prescription has a (-) minus sign next to it. Whereas, you are farsighted if there is a (+) plus sign next to it. Cylinder – Cylinder or CYL is used to identify how much lens power in your prescription is for astigmatism if you suffer from it. It may be that nothing is filled in for that part of the prescription at all. That basically means you either have no or very minor astigmatism that needs to be corrected. Axis – Now, the axis identifies the lens meridian that has no cylinder power for correcting astigmatism. The axis in your prescription will be measured in numerical form from 1 to 180. Where 180 is your eye’s horizontal meridian, 90 is the vertical meridian. Discover more about Sphere, Cylinder, and Axis here.