An eyeglass prescription represents your individual parameters for making corrective spectacle lenses.
OD (oculus dexter) – right eye
OS (oculus sinister) – left eye
Sometimes there is the abbreviation OU (oculus uterque), which means "both eyes"
Sph (sphere) – the optical power of the lens in diopters ("D"), expressed in negative or positive numerical values
Cyl (cylinder) – the optical power of cylindrical lenses for the correction of astigmatism, it can also be with a «+» or «-» sign
Ax (axis) – the axis of inclination of the cylinder in degrees from 0 to 180, it allows you to correct the refraction of light rays in a particular meridian
PD – the distance between the centres of the pupils in millimetres
Add (ADD power) – the difference in diopters between the distance vision and near vision zones, it is used for bifocal or progressive glasses when correcting presbyopia.
Prism – the power of a prismatic lens in prismatic diopters (p.d or triangle icon). Used in lenses for correcting strabismus, indicates the direction of the base of the prism: up, down, outward (towards the temple), inward (towards the nose)