We prescribe a prescription for glasses or contactlenses to achieve the highest amount of visual acuity possible for you.
Once the refractive error has been assesed and measured, a prescription is send out which you can use to get the desired glasses from a manufactorer.
The terms OD and OS specify which eye the correction is meant for. OD, from Latin Oculus Dexter, means right eye while OS, Oculus Sinister is Latin for left eye.
The term Sphere (S) refers to the spherical power of the lens, which is measured in dioptres (dpt) and is equal in all meridians. This is used to correct nearsightedness (myopia) or farsightedness (hyperopia). If the sign appearing before the number is minus (-), you are nearsighted. If it is plus (+), or has no sign at all, you are farsighted.
Cylinder (Cyl) indicates the lens power required to correct astigmatism. The cylinder value always follows the sphere value in your prescription. If you do not have astigmatism or you have a very slight astigmatism, your prescription will not include a cylinder value. Cylinder can be documented with a minus or plus sign and always include an axis (AX) to locate the correct meredian. At easee we always prescribe cilinders following the (-) sign.
The Axis (AX) always follows the cylinder in a prescription. The axis is documented in degrees and refers to the direction that the cylinder power is located to correct the astigmatism.