Abbreviations and Terms

Introduce:
An eyeglass prescription is a written order by an optometrist or ophthalmologist to an optician for eyeglasses such as reading glasses , optical frames It specifies the refractive power to which the eyeglasses are to be made in order to correct blurred vision due to refractive errors, including myopia, hyperopia, astigmatism, and presbyopia. It is typically determined using a phoropter or an automated refractor.

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

* D.V. 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.
* N.V. 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 cheap eyeglasses prescription forms use “ADD” in place of “N.V.” with a single box to indicate the additional refractive power to be added to the spherical of each eye.
* O.D. is an abbreviation for oculus dexter, Latin for “right eye.” (Some eyeglass prescriptions simply say “left” and “right” instead of “O.S.” and “O.D.”) Oculus means “eye” (as in “oculist,” an old term for an eye doctor).

* O.S. is an abbreviation for oculus sinister, Latin for “left eye”.
* O.U. is an abbreviation for oculi uterque, Latin for “both eyes”.
* A spherical correction corrects the refractive error of the eye by adding or subtracting refractive strength symmetrically, by the same amount, along the horizontal and vertical axis.
* A cylindrical correction corrects the astigmatic refractive error of the eye by adding or subtracting strength along the horizontal axis, the vertical axis, or a diagonal axis.
* The Axis is the horizontal, vertical or diagonal angle of the cylindrical correction. The axis is measured in a clock face that starts with zero degrees in the 9 o’clock (or west) direction, and increases through 90 and 180 degrees in a counter-clockwise direction.
Most eyeglass prescriptions will contain values here. The “spherical” and “cylindrical” columns contain lens strengths in diopters (see below); “axis” contains the direction of the cylinder axis in degrees.

* 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 muscular imbalance or other conditions (see vergence dysfunction) that cause errors in eye orientation. Prism correction is measured in “prism diopters”, and Base refers to the direction of displacement.
* PD is the distance between pupils, or Pupillary Distance, usually given in millimeters, and written as two values if the prescription is for bifocals or progressive lenses - these are the pupillary distances for the upper and lower lens. They differ due to pupillary convergence when looking at nearby objects.