The Sphere
This specifies the strength of lens required to correct your focus - a plus sphere to correct long-sightedness (hyperopia - difficulty focusing on close objects) and a minus to correct short sightedness (myopia - difficulty focusing on distant objects.)
The Cylinder & Axis
This measurement compensates for an astigmatism. So what's an astigmatism? An astigmatism is where the eye is shaped slightly like a rugby ball, not a perfect sphere like a football. This just means the eye has difficulty focusing at certain angles.
Reading Addition
The Add, short for Reading Addition, is the additional correction required for reading. This can be used to make either reading glasses or bi/vari-focal glasses.
The Pupilliary Distance
The PD, or Pupilliary Distance, is the distance in millimeters between the centre of your pupils. This isn't a major factor at lower prescriptions (roughly - spheres and cyl's less than two) unless you have exceptional features. For higher prescriptions it is recommended because it enables us to make your spectacles as accurately as possible.
You will sometimes see two values, one PD at distance and one PD for near vision (reading.)
Prism
A Prism is used to correct an imbalance in your binocular vision (the way your two eyes work together). If your prescription contains a prism we recommend you have your frames glazed at your opticians because accurate measurements will need to be taken when you're wearing the frames.
Examples of prescription forms
We have seen many varations of a prescription form so if in doubt fax over your prescription form and we will email you back with the details to fill out our prescription form online.
