Glasses Prescription Decoder

Eyeglass prescriptions use abbreviations such as OD, OS, SPH, CYL, AXIS, ADD, prism, base, and PD. This decoder translates the numbers you enter into careful plain-English explanations so the paperwork is less mysterious.

It does not verify that a prescription is medically appropriate, does not recommend products, and does not replace your prescribing clinician.

Follow these educational steps:

1. Enter right-eye (OD) and left-eye (OS) values you already have from a valid prescription.
2. Leave blank any fields that do not appear on your Rx.
3. Review each field explanation and open linked encyclopedia pages for deeper reading.
4. Use the educational notes about plano, minus/plus cylinder conventions, and ADD.
5. Do not change lens orders based solely on this website.

Sphere values relate to overall focusing power; minus spheres are commonly associated with myopia correction and plus with hyperopia or certain near needs — but the Rx must be interpreted as a whole by a clinician.

Cylinder and axis describe astigmatic correction orientation. ADD supports near focusing in multifocals. Prism addresses binocular alignment needs when prescribed.

The decoder will not tell you which glasses to buy or whether your Rx is “strong” or “bad.”

It will not convert a glasses Rx into contact lens parameters. Contact lenses require a separate, valid contact lens prescription.

Important limitations:

• Notation conventions (plus vs minus cylinder) can look different while representing equivalent corrections after transposition.
• Handwritten Rx quirks and OCR mistakes can confuse automated parsing — verify against the original.

If numbers on a new Rx confuse you, ask the prescribing doctor or dispensing optician. Seek prompt care for sudden vision changes rather than re-decoding an old Rx.