The SPHERE is always written first. If this number has a + infront of it, it indicates you are long sighted. Generally speaking you find things in the distance easier to see than things up close.
If the number is preceded by a - (minus), you are short sighted. Distance objects being more blurry than close up ones.
It is possible you are neither long sighted nor short sighted, in which case this first number will be either a “0”, written as “plano” or expressed as an infinity sign ∞.
The second figure will be the CYLINDER value. This is relevant if you have “astigmatism”. Your Optician will often refer to this as you having rugby ball or egg shaped eyes.
This can also be a + or - value so take care when entering the details.
Next is the AXIS. This is a value (actually a degree) between 1 and 180 instructing what orientation to make the lenses. This will only be present if there is a CYLINDER power present.
If you need different powered glasses for reading than you do in the distance, including bifocals and varifocals, then you will have a reading ADD. Sometimes this will be written as NEAR.
Similarly, if you require glasses for use at a distance a little further than reading, ie for a vdu, this may be recorded as an INTERMEDIATE power.
PRISM is normally left blank, unless you need some help to allow your two eyes to work together. If there is a number for prism, it will be followed by a direction that it is required in. This will be either UP, DOWN, IN or OUT. Take note that values and directions may be different for each eye and can even be different for Distance and Reading glasses.
If you think your prescription contains prism then get in touch to let us be sure that we make your glasses perfectly for you. We can offer up to 3D of prism, please contact us directly if your prescription requires more. Incorporating prism may involve a small fee.
PD - Pupillary Distance
When ordering your glasses we are going to want to know your Pupillary Distance or “PD”. This is simply the distance in mm between your eyes. Average values would typically be between 60mm and 66 mm.
Each lens we cut and glaze into your glasses will have an optical centre. This is the sweet spot on the lens has the very best optical properties. By making sure this spot is aligned directly in front of your pupils we can be sure you will experience the very best vision possible through your glasses.
An incorrect PD can lead to visual strain, distortion, headaches and in rare circumstances double vision. This is why it is necessary to get as accurate a measurement as possible.
Although your PD will me measured during your sight test, it is rarely recorded on your prescription. You can request this information from your optician, use our guide to measure it yourself or alternatively send us an old pair of your glasses. We have the machinery to measure your PD from these and will return them by post with your new spectacles.