How to decipher the code behind your prescription

IF YOU are able to decode the hieroglyphics of a prescription you can get a better understanding of what is going on with your eyes – and what you need to buy.

SPHERE

Sometimes abbreviated to Sph. This reveals if you are long or short-sighted. A ‘+’ symbol is for long-sighted people and indicates you have trouble reading close up.

A ‘-’ symbol is for shortsighted people where objects in the distance are blurred. The higher the number, the more serious the condition.

If you are long-sighted (hyperopia) you get fitted with convex curved lenses. Those who are short-sighted (myopia) get concave lens curves. Of course, you may well have a combination of the two – when you will be fitted with varifocal, bi-focal or progressive lenses.

CYLINDER

‘Cylinder’ – or Cyl – is a section where the shape of your eye is noted. If your eye is shaped like a rugby ball you have astigmatism that makes your eyesight blurred and needs correcting.

AXIS

This denotes the angle in the frame that the lenses must be positioned – to help with spectacle glazing. It may include additions to a prescription, such as if a user needs extra strength for reading small-print.

BACK VERTEX DISTANCE

BVD indicates the distance in millimetres between the front of your eye and the lens. This can be important for those with a high prescription.

FRAME CODES

Frames have their own hidden codes. If you look on the inside of your glasses’ arm you may find figures that show measurements. For example, ‘48 19 145’ means that the lenses are 48 millimetres in diameter; the nose bridge is 19 millimetres wide and the arms are 145 millimetres long.