An eye prescription holds the readings that your optometrist records each time you go for an eye test. These numbers on the prescription slip/card are the key to your correct power. Whenever you wish to buy power eyeglasses/sunglasses, these values come in handy. It might look tricky at first, but there’s an easy way to decode these abbreviated terms & set of +/- readings.

Let’s start with the basics -

  • + indicates long-sightedness or Hyperopia
  • - indicates correct near-sightedness or Myopia
  • RE/ O.D. stands for Oculus Dexter or Right Eye
  • LE/ O.S. stands for Oculus Sinister or Left Eye
  • PD is Pupillary Distance
  • DV stands for Distance Vision
  • NV stands for Near Vision

Let’s go ahead and know in detail what do the other terms in your eye prescription mean:

Sphere (SPH)

SPH or Sphere is the power of the lens required to correct a single vision defect. This denotes if a person has myopia or hyperopia. It is measured in Diopters (D). The values can be different for both the eyes.

  • Corrects Myopia & Hyperopia
  • Ranges from 0.00 to +/- 20.00 D
  • Higher prescription means high degree myopia/hyperopia

Cylinder (CYL)

CYL or Cylinder power indicates that the cornea of the eye is not perfectly sphere in shape. If you have some numbers in your CYL grid of your prescription, you will require eyeglasses to correct astigmatism.

  • Corrects Astigmatism
  • Ranges from 0.00 to +/- 4.00 D
  • Higher prescription means high degree astigmatism


Axis reflects the exact orientation of your astigmatism. It is measured in Degrees. If your prescription has a CYL value, it is sure to have an axis value too. If your prescription holds a CYL value and no axis or vice versa, it means your prescription is either incomplete or incorrect

  • Indicates degree/direction of astigmatism
  • Ranges from 0 to 180 Degrees
  • Always present along with Cylinder Value

ADD (Addition)

Add or Near Addition power is added on the lower part of the multifocal/bifocal lenses to correct presbyopia. This helps one in performing close-up tasks with ease.

  • Indicates the additional reading power
  • Used in bifocals, progressives and reading glasses
  • Added at the bottom half of the lens for people with presbyopia

Pupillary Distance (PD)

Pupillary distance is an important measurement from the center of one eye to the center of another. This is used to mark the exact optical center in your lenses which further helps to view things properly and without any eye strain.

  • Distance between the centers of two pupils
  • Ranges from 50 to 70 mm
  • Incorrect PD value can cause eye strain & visual distortion

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