Prescriptions Explained

Prescriptions Explained

After you have had your eye examination, we will be able to tell you whether you need glasses or if your prescription has changed from your last visit. You will receive a copy of you prescription, which can look a little bit confusing at first, as it is full of measurements, numbers and abbreviations. So, if you’re not sure what your prescription means, we have a handy guide here to help explain.

It’s important to understand your prescription, as it can give you a full picture of your vision and whether it is worsening over time.

What does your prescription mean?

Your prescription is usually displayed in a table with abbreviations and numbers to indicate the results of your eye test. Here we’ll explain what each one means, so you can make more sense of your vision capabilities.

SPH refers to ‘sphere’, which indicates the amount of lens power. This is measured in dioptres (D). You might see a plus or a minus sign in front of the measurement; a plus sign means you are long-sighted, while a minus sign means you are short-sighted. The higher the number, the stronger your prescription.

CYL is short for ‘cylinder’, which indicates if you have astigmatism. Astigmatism is caused by an abnormally-shaped cornea, meaning the curvature of the cornea or lens is not uniform and can affect your vision. A low number, such as 0.25, shows that your eyes are only slightly irregular. High numbers such as 3.00 can show that your eyes are quite oval in shape.

AXIS indicates the direction of the astigmatism, and is measured in degrees. This can help to make sure your lenses are positioned correctly to help refract the light for optimal vision.

PRISM can tell you if there is an imbalance in your eyes, and if any correction is needed to align them. BASE is related to your prism prescription and tells the lens lab where to direction the prism in the lens.

If you are over the age of 40, you might see a number in the ADD box. This section will indicate if you need a reading addition to your prescription to help you see better at near.

If you have any further questions about your prescription, don’t hesitate to get in touch and we’ll be happy to answer them!