Your Rx is what an ophthalmologist (an MD) or optometrist (a doctor of optometry) provides to correct your vision with a pair of eyeglasses with corrective lenses.
An Rx will have horizontal rows or vertical columns. The top row or first column will always be for the right eye, abbreviated as OD. The second row or column will always be for the left eye, abbreviated as OS.
Each row of an Rx has three main sections: Sphere (SPH), Cylinder (CYL), and AXIS. The SPH section corrects nearsighted or farsighted vision. The CYL and AXIS sections correct an astigmatism.
There may also be a fourth section on the Rx , NV-ADD (for Near Vision-Reading ADDition), which could be used to order a pair of bifocal or progressive glasses with a close-up vision section in the bottom part of the lens.
The SPH and CYL numbers will have a plus(+) or minus(-) sign and NV-ADD has always plus(+) sign.
OD: Latin for Oculus Dexter, meaning the right eye.
OS: Latin for Oculus Sinister, meaning the left eye.
OU: Latin for Oculus Uterque, meaning each eye.
PAL: Progressive Addition Lens: sometimes on a Progressive Rx an eye dr. will write two different numbers for the NV-ADD, perhaps +2.25 and +2.50, to increase the reading power in the NV-ADD for Progressive lenses.
PD (Pupillary Distance): the PD is the measurement of the distance between your pupils. This is needed for the manufacturer of the eyeglasses to know where to place the optical center on each lens, so you can see well with the glasses.
PL: Plano. This is in the SPH section of an Rx, it means no nearsighted or farsighted correction is needed.
RX: a prescription.
SPH: the first section on an Rx. It corrects nearsighted or farsighted vision.
UV: the abbreviation of ultraviolet. UV light is invisible to the human eye, but it is UV light that gives us a sunburn, and too much exposure to it can damage the eye. All of the lenses we offers come with 100% UV protection, for free.
VA: Visual acuity: how well the eye can see. Sometimes this may be written on an Rx, with a number such as 6/6. This would indicate that with eyeglasses made to this Rx, the vision would be corrected to 6/6 vision.