All You Need to Know About Your Glasses Prescription

As a glasses wearer, your prescription is an important personal document. The certificate issued by your optician provides details about your individual correction values and essential information about your new glasses. Here, we explain everything you need to know.

Your prescription includes the values required to make glasses or sunglasses with corrective lenses. Keeping it up-to-date is crucial, especially if you’re travelling and need a quick replacement if your glasses break. It also makes ordering glasses online simple. Ensure you regularly check your values (more on eye exams) to maintain optimal vision.

How Much Does a Glasses Prescription Cost?

Generally, nothing – when you buy new glasses, your optician provides the prescription for free. If your values need to be determined for the first time or updated, you may incur costs.

Glasses Prescription Dictionary – Explained  

Basic Data: Understanding the Abbreviations

In addition to lens strength and material, your prescription often includes details about the frame and the manufacturing date. You'll also find the following abbreviations:

• D: Distance glasses

• N: Near glasses (e.g. reading glasses)

• R or OD - (Oculus Dextrus): Right eye

• L or OS (Oculus Sinister): Left eye

Understanding the Prescription

These are the values your optician needs to correct your vision. Specifically, these include:

SPH (Sphere):

Indicates short- or long-sightedness in dioptres. Negative values signify short-sightedness (marked with "–"), while positive values indicate long-sightedness (marked with "+"). The higher the dioptre number, the stronger the lens. Refractive power is given in steps of 0.25 dioptres (e.g., 0.25/0.5/0.75/1). Values are marked "R" for the right eye and "L" for the left eye.

CYL (Cylinder):

Relevant for astigmatism. This value follows the SPH value and corrects the uneven curvature of the eye. It is given in 0.25 steps and can be negative or positive.

A (Axis):

Also for astigmatism. Necessary if a cylinder value is present. The axis indicates the orientation of the cylinder in the lens to correct astigmatism, ranging from 0 to 180 degrees in 1-degree steps.

Prism:

Indicates a need to correct eye alignment issues, measured in prism dioptres. It helps address double vision or headaches by enabling both eyes to work together better. Not all prescriptions will include a prism value.

Base:

Shows where the prism should be placed in the lenses. Indicated by abbreviations: BU (base up), BD (base down), BI (base in, towards the nose), BO (base out, towards the ear). Ensures proper prismatic correction.

PD (Pupillary Distance):

Pupillary distance is the measurement from the centre of one pupil to the centre of the other and is crucial for fitting glasses. Measured in millimetres, it significantly impacts vision quality, especially with higher corrections. Ensure your prescription includes the PD value for accurate fitting.  

ADD (Addition Value):

Used for varifocal and reading glasses, this value indicates the difference between near and distance corrections. For instance, with a distance value of -1.5 dpt and a near value of +1.0 dpt, the addition value is 2.5 dpt.

Tip: If you lose your glasses prescription, contact the optician who made your last pair. They will have your data saved and can issue a new one. If you still have the invoice for your old glasses, check it first as the details are often listed there.