Eyeglass Prescription - Abbreviations and Terms

Abbreviations and Terms

Similar to medical prescriptions, eyeglass prescriptions are written on paper pads that frequently contain a number of different abbreviations and terms:

• DV is an abbreviation for distance vision. This specifies the part of the prescription designed primarily to improve far vision. In a bifocal lens, this generally indicates what is to be placed in the top segment.
• NV is an abbreviation for near vision. This may represent a single-vision lens prescription to improve near work, or the reading portion of a bifocal lens. Some prescription forms use ADD in place of NV with a single box to indicate the additional refractive power to be added to the spherical of each eye.
• OD is an abbreviation for oculus dexter, Latin for right eye. Oculus means eye. In some countries, such as the United Kingdom RE (right eye), LE (left eye), and BE (both eyes) are used. Sometimes, just right and left are used.
• OS is an abbreviation for oculus sinister, Latin for left eye.
• OU is an abbreviation for oculi uterque, Latin for both eyes.
• A spherical correction corrects refractive error of the eye with a single convergent or divergent refractive power in all meridians.
• A cylindrical correction corrects astigmatic refractive error of the eye by adding or subtracting power cylindrically in a meridian specified by the prescribed axis.
• The axis indicates the angle in degrees of one of two major meridians the prescribed cylindrical power is in. Which major meridian is referenced is indicated by the cylindrical correction being in plus or minus notation. The axis is measured on an imaginary semicircle with a horizontal baseline that starts with zero degrees in the 3 o'clock (or east) direction, and increases to 180 degrees in a counter-clockwise direction.

Most eyeglass prescriptions will contain values here. The spherical and cylindrical columns contain lens powers in diopters (see below).

• Prism and Base are usually left empty, as they are not seen in most prescriptions. Prism refers to a displacement of the image through the lens, and is used to treat eye muscle imbalances or other conditions (see vergence dysfunction) that cause errors in eye orientation or fixation. Prism correction is measured in "prism diopters", and Base refers to the direction of displacement.
• Pupillary Distance (PD) is the distance between pupils, usually given in millimeters, it is sometimes known as the interpupillary Distance (IPD). It is written as two values if the prescription is for bifocals or progressive lenses - these are the pupillary distances for the distance and near fixation (essentially, the upper and lower part of the lenses). They differ due to pupillary convergence when looking at near objects. Additionally, an eyeglasses prescription may include a monocular pupillary distance ("monocular PD"). These measurements indicate, in millimeters, the distances from each pupil to the center of the nose where the center of the frame bridge rests. PD measurements are essential for all spectacle dispensings, monocular PDs being essential in progressive lenses and for those with high prescription. PDs can be measured using a pupilometer or by using a ruler. In countries such as the United Kingdom, PD measurement is not a legal requirement as part of the prescription and is often not included.
• Back vertex distance (BVD ) is the distance between the back of the spectacle lens and the front of the cornea (the front surface of the eye). This is essential in higher prescriptions (usually above ±4.00D) as slight changes in the distance between the spectacles and the eyes above this level can cause the patient to perceive a different power, leading to blur and/or other symptoms.