How to Read a Contact Lens Prescription

How to Read a Contact Lens Prescription

Feel Good Contacts make buying your contact lenses online even more accessible, as we don’t need to see your prescription before you order. We trust that you have an up-to-date prescription and know which lenses you need. If you don't have a copy to hand when ordering and can't remember your specifics, you can even find the details of your prescription on the side/end of your last contact lens packaging or on the blister packs that contain your contact lenses.

What is my contact lens prescription?

A contact lens prescription contains all of your visual specifications and lets you know which type of lenses you need. To help make things that little bit simpler, we’ve written a guide on everything you need to know about your prescription when ordering contact lenses online.

It's essential to note that a contact lens prescription is not the same as a glasses prescription. So, if you’re a glasses wearer who wants to try out contact lenses, you’ll need to go for a lens fitting to find out your requirements.

You should have been given your contact lens prescription from your optician after your last lens fitting. If not, then don’t hesitate to request your prescription, as it’s your legal right in the UK to own a copy. Alternatively, you can find it on the box of your contact lenses or on the blister packs containing the lenses.

Where can I find my prescription?

Your prescription can be found on the end or side of your contact lenses box, on the blister pack containing your lenses or on the piece of paper given to you by your optician after an eye test when you go for your contact lens fitting.

Can you buy contact lenses without a prescription?

Whilst you don't need a physical prescription when purchasing contact lenses from Feel Good Contacts, you'll need to understand your prescription so that you can purchase your lenses correctly.

How do I read my contact lens prescription?

A prescription usually includes a base curve, diameter, and power (sphere). The prescription for your left and right eye may differ and for this reason, you'll find them written separately. If you have astigmatism, you'll find additional figures for cylinder and axis. Those with presbyopia will addition and dominant figures on their prescription.

You'll also find the name of your contact lenses and the expiry date on your prescription.

In some instances, you'll also find how often to replace your lenses written on your prescription; for example, it may say whether they are daily, weekly, monthly etc.

If you're choosing coloured contact lenses, you'll also find this information written on your prescription.

Below are some examples of how your prescription may be written:

When do contact lens prescriptions expire?

The expiry date is typically a year from when your prescription was written.

What do my contact lens prescription figures mean?

Although you don't need your contact lens prescription when purchasing your lenses from Feel Good Contacts, it is important to have a thorough understanding of what your prescription is.

Measurements given in a prescription include a base curve, diameter, power as well as cylinder and axis for those with astigmatism and ADD (addition) figures for presbyopia. You'll find that your left eye and right eye prescriptions may vary and for this reason, you'll see them listed separately. Below we have listed what each measurement means:

Standard box
Standard box

Base curve (BC) – This figure determines the curve of the lens so that it can fit the curvature of your eye. This number is typically written in millimetres or sometimes given with the terms: flat, steep or median.

Diameter (DA) – Simply informing you of the width of the lens, this measurement is in millimetres.

Power/Sphere (PWR/SPH) – Power or Sphere indicates whether you are short-sighted or long-sighted. A plus sign (+) is for long-sightedness, and a minus sign (-) is for short-sightedness. The higher the number, the stronger the visual correction offered by the lens.

Prescription figures for astigmatism

Axis (AX) – Those with astigmatism have an unusual curve to their eye, which requires angular visual correction. The axis is a figure between 0 and 180, which determines how much of an angle of correction your lenses offer.

Cylinder (CYL) – This is a figure, specifically for toric lenses, that lets you know the severity of astigmatism and the additional visual requirements.

Prescription figures for presbyopia

Addition (ADD) - The Addition figure determines the level of correction needed for close distance visual clarity. This figure is between 0.50 and 3.00 or is referred to as low, medium or high.

Dominant (D) - multifocal contact lenses offer visual correction through a ‘dominant’ and ‘non-dominant eye’. The figures ‘D’ and ‘N’ are used to indicate which is which, respectively. You'll also find an expiration date on your prescription. The expiration date is typically a year after your check-up.

Here is a comparison of different contact lens prescriptions from opticians:

The examples below show various contact lens prescriptions from opticians alongside examples of how these prescriptions should look when entered on our website.

It would be entered on our website as follows:

Specsavers Prescription

Optical Express
It would be entered on our website as follows:

Optical Express Prescription

Smith & Swepson
It would be entered on our website as follows:

Smith & Swepson Prescription

Independent opticians
It would be entered on our website as follows:

Independent opticians Prescription

Handwritten standard prescription
It would be entered on our website as follows:

Handwritten standard prescription

Handwritten Multifocal prescription
It would be entered on our website as follows:

Handwritten Multifocal prescription

What is the strongest contact lens prescription?

Contact lenses can be prescribed for extreme degrees of myopia, even for those who need correction of more than -20 Dioptres. Some lenses can go over -30 Dioptres.

For monthly soft contact lenses, the highest level of corrective power is about -12 Dioptres. The highest level of corrective power for people with astigmatism is approximately -9 Dioptres of Sphere.

How to understand an eyeglass prescription?

Understanding an eyeglass prescription is different from a contact lenses prescription. Your prescription for eyeglasses may have numbers listed under the headings od and os, which are Latin abbreviations for oculus dexter and oculus sinister, meaning left and right eye.

Positive powers mean long-sightedness whereas minus powers mean near-sightedness. These powers are measured in dioptres and found in front of numbers used to measure the correction or focusing power. The further away the number is from zero, the worse your eyesight is, meaning you'll need a stronger prescription.

Those with astigmatism will find three numbers listed in their prescription:

  • S or sph or sphere, representing the degree of near-sightedness and farsightedness.
  • C or cyl or cylinder, which refers to astigmatism.
  • Axis-this reveals the orientation of astigmatism and is a number between 0-180 degrees.

Can I use my glasses prescription for contact lenses?

You cannot use your glasses prescription to purchase contact lenses. Both require a set of different measurements as they differ in their fitting characteristics.



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