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Help understanding you pescription

Understanding Your Prescription

We want to make your shopping experience as easy as possible therefore here is some information that will help you understand your prescription.

Our staff are available to help you during office hours on 0345 548 2020 or alternatively you can fax or email a copy. This is a sample of how most prescriptions are issued

Understanding Your Glasses Prescription

There are different terms used by opticians and here are some of the meanings.

  • Distance Vision = Dist, DV or Distance>
  • Near Vision = Near, NV or Reading>
  • Rx = prescription
  • Right Eye - R, RE or OD
  • Left Eye - L, LE or O.S

A zero may be written in SPH or CYL as 0 or 0.00, Plano or PL
The negative sign for SPH or CYL values may be written before, above or below the number.
The addition sign may be used for reading glasses.

Sphere (Sph)

This is the strength or power of lens required to correct your vision.
A plus (+) sphere is used to correct long sightedness (Hyperopia), where there is difficulty in focussing on close objects. The plus sign may be placed before, after or above the value, or there may be no plus sign.
A minus (-)sphere is used to correct short sightedness (Myopia) where there is difficulty in focussing on distant objects. The minus sign may written before, after or above the value.
Where there is no value this may be entered as 0 or Plano or PL or using the infinity sign, ∞

Cylinder (Cyl)

A cylinder value is used to correct astigmatism, this is where the eye, instead of being perfectly round has changed to more of a rugby ball shape.

Not everyone has a Cyl value on their prescription, or it might be only on one eye. If there is no value on your prescription then leave this field empty. This Cyl value may be in either plus or minus form. The plus or minus sign may be written before, after or above the value. If there is no plus or minus sign it is assumed that the value is plus. A Cyl value is always accompanied by an Axis value.


The axis value tells us how to align the cylinder correction in you prescription. You will only have an axis value if there is a cylinder value.
Enter a number between 1 and 180 (degrees) for the axis to which the cylinder is to be orientated.

Addition (Add or Reading Addition)

This power or value is the additional magnification required for preparing glasses for reading or computer work.
It may be included as a separate value on prescriptions for making bi-focal or varifocal lenses, which have both the distance and near correction powers. This value is only required if you select single vision reading lenses.

Pupil Distance (PD)

Your Pupil Distance (also known as Inter Pupillary Distance and PD) is the distance between the centres of your pupils usually measured in millimetres. It may be expressed as a single number e.g. 54mm or as a monocular PD, e.g. R31mm/L31mm where the measurement is given separately from the centre line for each eye. The normal range for the PD in the adult population is 54mm - 68mm.

Prism & Base

These are absent from most prescriptions. A prism is used to treat muscular imbalance or other conditions that cause errors in eye orientation.

A prism will be used to displace the image seen by the eye through the lens. The base refers to the direction of the displacement. If you have a prism and base value on your prescription you will need to inform us about this separately and provide a copy of your prescription.

Please remember our qualified Optometrist is on hand to offer assistance on 0345 548 2020 or email

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