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Home Patients' Zone How to Read Your Glasses Prescription

How to Read Your Glasses Prescription

What SPH, CYL, AXIS and ADD mean

Your glasses prescription is a short code that tells the optician how to make lenses for each eye. Here is what each part means.

TermWhat it means
RE / OD and LE / OSRight eye and left eye (OD and OS are the Latin abbreviations). OU means both eyes.
SPH (sphere)The main power of the lens, in dioptres (D). Minus (−) means short sight (myopia): you see near things better than far. Plus (+) means long sight (hypermetropia) or help for reading.
CYL (cylinder)Extra power to correct astigmatism, where the front of the eye is shaped more like a rugby ball than a football. If this box is empty, you have little or no astigmatism.
AXISA number from 1 to 180 that shows the direction of the cylinder. It is not a power; it is an angle, so 180 is not "worse" than 90.
ADDExtra plus power for reading, usually needed from about age 40 (presbyopia). It is added to the distance power in bifocal or progressive lenses.
PRISM / BASEOccasionally prescribed to help the eyes work together, for example in some types of double vision.
PDPupillary distance: the distance between the centres of your pupils in millimetres, so the lenses are centred correctly.
V/A, 6/6, N6Your vision with the glasses. 6/6 is normal distance vision; N6 is a small reading print size.

Examples

  • RE −2.00 DS: short sight of 2 dioptres in the right eye, with no astigmatism (DS means dioptre sphere).
  • LE −1.50 / −0.75 × 180: short sight of 1.50 D plus 0.75 D of astigmatism at axis 180.
  • ADD +2.00 (both eyes): reading addition of 2 dioptres, typical at about 50 years.

Common questions

  • Why did my number change? Children's numbers often rise with growth; adults change slowly; diabetes, cataract and some medicines can also change your power. A big change deserves an eye examination.
  • Why is the computer test different from the final prescription? The machine (autorefractor) gives a starting point. The final prescription is checked and fine-tuned with you looking through lenses, and sometimes after drops in children.
  • Is a contact lens prescription the same? No. Contact lenses sit on the eye, so for stronger powers the number is different, and the lens fit and size are also prescribed.
  • How long is a prescription valid? Usually 1–2 years for adults and 6–12 months for children, or sooner if your vision changes.

Related: lens coatings guide, what 6/60 or 3/60 means, understanding myopia.

Questions?

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