A great mystery which we often have to help you all unravel is the prescription that your optician gives you, the power or strength of your lenses. So let’s start at the beginning and give you some background information on what those scribbled numbers mean!
The lens power is written in a unit of measurement called a Dioptre, and it’s all about the focal length of your lenses. Your first task when sending it to us is to make sure your Optician has written it clearly! Bless them – they’re as bad as Doctors! So check with your Optician if you’re not sure.
The top line of the prescription box is the power of your lenses for distance. This covers TV, walking around, driving and general wear. Then you will have intermediate and reading strengths. Reading is for very close work and small detail, like threading a needle and reading. Intermediate is for large print at arm’s length, so computer screen and reading music.
Now for the science bit!
Sph is short for sphere power, which is your amount of short or long sightedness. The higher the number, the more correction you need. It has a plus sign if you’re long sighted, minus for short.
Cyl is short for cylinder, and this is the amount of astigmatism you have. It simply means that your eye is shaped more like a Rugby ball, so you need one power to correct the long part of the Rugby ball, and one for the short. Again, there will be a plus or minus sign.
Axis is the angle of your Rugby ball! As it’s an angle don’t bother looking for a plus or minus sign!
If you don’t have an astigmatism then both the cyl and axis boxes will be empty.
Add is the extra power you need for reading, and we add it on to your distance prescription. An add power is usually the same for both eyes.
Prism is relatively unusual, and this makes your two eyes work together.
So there you go, a little bit of extra knowledge, but all you have to worry about is copying it down for us, and we’ll do the rest!
