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Understanding your prescription...


Now comes the tricky part, you've chosen your frames, now all you need to do is enter your prescription, if only life was that easy. Well it can be, we have put together a guide to help you make sense of your prescription. Often opticians will use barely legible writing on their prescriptions so that only they can read them. Were here to help you.

Once you have had you eyes tested at your local optician, you should receive a copy of your prescription. It is the law for the optician who tested your eyes to issue you with a copy of your prescription. Under the UK Opticians Act of 1989, it is the obligation of any optician to provide you with a prescription. Your prescription needs to be less than 2 years old. If it is older than that, you will need to get your eyes tested again.

Most prescriptions that are printed will be straight forward to understand and just need to be copied into the add your prescription section. You may also have a hand written prescription, if this is the case then you may need help in understanding what is written down. If this guide still doesn't help then you can phone on 0844 310 2020, fax to 0844 310 20 10 or scan and email to

Sphere (SPH)

SPH stands for Sphere, all prescriptions will have one of these. It will either have + or a - sign which indicates whether you are long or short sighted. The values will go up by 0.25 increments. At See In Style we only cater for prescriptions of up to +/- 8.00. This is because we feel that anyone with this type of prescription requires more specialist attention at your local opticians.

The +/- signs are written either beside the value or above the value. Sometimes instead of writing a - sign next to the figure opticians will just omit the full stop, e.g. instead of -1.5 they will just write 15. It's important that you can confirm the sign. Sometimes you may find a figure that looks like an 8 on its side, that's the symbol for infinity, also knows as a plano lens. If you have any difficulties in understanding any part of your prescription you can fax or scan it to us at and we will take care of it for you.

Cylinder (CYL)

CYL stands for Cylinder, not all prescriptions have this, if you have a value in this box you have an astigmatism which means that your eye shape is rugby ball shaped. It will either have a + or a - sign like the Sph value. The values will also go up in 0.25 increments and will go up to +/- 4.00. Again the sign will be either beside or above the value like the Sph value. Its fairly common to have the same value in both eyes and if you have an axis value you should also have a CYL value. Occasionally an optician may record the figure as DS, which simply means no astigmatism.


You should also have an Axis reading when you have a CYL reading, this will range from 0 to 180. Every Cyl value MUST have an Axis value. Note It is possible for one eye not to have a CYL/AXIS reading which means that eye doesn't have an astigmatism and will only have a value in the Sph box.

Add/Near addition

This is the value that needs to be added to the Sph value so that reading or intermediate glasses can be made for use with computer or reading glasses.

You will find this value on your prescription normally under your distance prescription. You may have two additions if you need them. One would be for computer and the other would be for reading. You may just have one reading add in which case this will be fine for computer and reading.


A balance lens usually means that there is very little vision or no vision at all in one eye. This is written down because the optician wants to match the weight and thickness of the other lens so they look equal. If you have this on your prescription please enter it on to our See In Style add prescription section as it appears on the prescription


Prisms are used to correct lazy eyes or an eye with a squint. Please enter these values in the prism section when you are adding your prescription.

PD (Pupillary Distance)

This measurement is the distance between the customers eyes and this measurement is needed because for any pair of glasses to work optimally the customers pupils need to be in line with the centre of the lenses in the frame. The PD measurement is never written down on your prescription but you optician will have it if you have bought glasses from them before. Your optician may give you your PD if you ask nicely or they may charge you a small fee for you PD measurement. The PD measurement is only taken at the time of dispense e.g. when you buy glasses, so if you haven't bought glasses from them before then they are likely not to have your PD on record. If you prefer not to ask for your PD, See In Style will use an average PD measurement. Often using an average PD will give most people the perfect glasses, but sometimes if you have a strong prescription they will cause eye strain or discomfort, simply let us know and we can replace your glasses for you.