SPH stands for spherical power and describes the degree of nearsightedness or farsightedness.
A positive value, or a prescription with a plus-sign (+), means that the child is farsighted. If one sees a negative value (-)
that means the child is nearsighted.
In general, the further away from zero the number on a child's prescription, the more spectacle correction needed and the stronger
Cylinder is the measure of astigmatism - simply put, the front of the eye is not completely round but has more of a rugby ball shape.
- + : farsighted, or longsighted prescription: hyperopia.
- – : nearsighted, or shortsighted prescription: myopia.
- 0, Pl, or Plano : no error
A person with astigmatism does not see clearly either at distance or at near which can result in blurry vision & sometimes cause headaches.
For some prescriptions there will be no astigmatism correction for one or both eyes. An eye doctor may just write the sphere power alone, or may use abbreviations like sph (“sphere”) or DS (“diopters sphere”).
If there is a CYL number, there will also be an axis number.
The axis indicates the orientation of astigmatism and is measured in degrees from 1 to 180
stands for addition and is used with multifocal lenses (i.e bifocals). If a child needs bifocals, there will be a number here. ADD is additional magnification which helps with vision at close range.
is used to help people with muscular imbalance in their eyes. Prisms can help to reduce eyestrain and correct double vision.
P.D., or Pupillary Distance
, is the distance between the centre of the pupils, which is used to position the lenses in the frames.
Pupil distance is measured in two ways :
which is a pupil-to-pupil measurement, this type of measurement will be between 42-60 mm for most children
which is a per-eye measurement from the pupil to the middle of the face - example : 25/24.5 - the first number (25) is for the right eye (O.D.) and the second number (24.5) is for the left eye (O.S.) - total these together to get 49.5 binocular