How to read your prescription

This is how you read a prescription for your soft contact lenses

A prescription for contact lenses consists of the brand of the contact lens and the specifications of the prescription. Per brand, lenses can have specific properties that are essential for that type of contact lens, therefore the brand of the contact lens is usually part of the prescription.

The prescription of your lens also consists of the following data:

On most prescriptions or contact lens packaging, names and/or abbreviations will be used as indicated below. However, this can differ per prescription, packaging and even brand. If you are not sure or have any questions, please feel free to contact us.

Please note: prescriptions for glasses do not just translate into a prescription for soft contact lenses. Do not experiment. That only costs you time, money and annoyance and, in the worst case scenario, a big eye infection, with all its consequences. If you have never worn contact lenses, go see an optician first, and let your eyes be measured and checked specifically for the use of contact lenses. The optician is the best person to help you on your way in the use, wear and maintenance of contact lenses.

Right eye

On your prescription is stated as: "right", or "OD" or "O.D." or "RO", the data for the right eye ("oculus dexter" in Latin).

You will usually find this abbreviation before the prescription details, on the relevant row or column of your prescription.

Left eye

On your prescription: "left" or "OS" or "O.S." or "LO", the data for the left eye ("oculus sinister" in Latin).

You will usually find this abbreviation before the prescription details, on the relevant row or column of your prescription.

Both eyes

On the packaging: "OU" or "O.U.", the data for both eyes ("ocular uniter" in Latin).

It may happen that you have the same prescription for both eyes, in which case it is possible that it is stated "OU" on your prescription rather than "OD" or "OS".

Power

On your prescription, it says: "Sphere" or "SPH" or "Power".  On the packaging: "PWR" or "SPH".

This value is the "Power" of your lens, sometimes also indicated as "sphere" or "power".

The power of your lens is measured in dioptres (D).

The power is usually between -10 and +10.

The power can also go up to -20 but that is rare in soft contact lenses. The range of powers is often in increments of 0.25, and this is true for most soft contact lenses and goes from -6 to +6. From 6 "-" and "+" it changes to steps of 0.50.

Myopia, Hyperopia and Presbyopia

For myopia or nearsightedness, the power of the lens is preceded by a "-" sign.

For hyperopia or farsightedness, the power of the lens is preceded by a "+" sign.

For presbyopia, the power of the lens is also preceded by a "+" sign.

Base curve

On your prescription: "Base Curve" or "curve" or "basis" or "radius". On the packaging: "BC".

This value is the "base curve" or "curvature" of the lens and indicates the fitting.

The base curve is given in millimetres and is usually between 8mm and 10mm.

Only in rare occasions, it gets marked with a value such as "flat", "medium" or "sphere".

Diameter

On your prescription: "Diameter" or "DIA". On the packaging: "DIA".

This value measures the diameter of your lens.

The diameter is indicated in millimetres and is usually between 13mm and 15mm.

Addition

On your prescription: "Addition" or "add". On the packaging: "ADD".

This value measures the "addition" for bifocal or multifocal lenses to also be able to see from close by sharply.

The addition of the lens is always preceded by the "+" (plus) sign.

The values of the addition are limited and usually, only 3 or 4 values are available, from 1 to 4, in increments of 0.50. They are often also referred to as LOW, MED, or HIGH.

Cylinder

On your prescription: "Cylinder" or "CYL". On the packaging: "CYL".

This value indicates the degree to which the lens compensates for astigmatism.

The cylinder of your lens is measured in the same way as the power, in dioptres (D).

The cylinder of the lens is always a negative value and is preceded with the "-" (minus) sign.

The range of values of the "cylinder" is limited and usually, only 3 or 4 values are available, from -0.75 to -3.75 in increments of 0.50.

Axis

On your prescription: "As" or "Axis" or "Ax". On the packaging: "Axis" or "AX" or "X".

This value indicates for astigmatism what the orientation of the lens on the eye should be so that the compensation of the "cylinder" is on the right place on the eye.

The axis is measured in degrees and the value can be between 0 and 180, usually in steps of 10 degrees. For daily lens often even more limited to only 3 or 4 standard values such as 20, 90, 160 and 180, but this "range" is being continually extended.

The axis is usually indicated with 3 digits. 70 degrees becomes "070", for example, and often is it preceded by an "x" sign.

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