An annual eye exam is important for everyone, even children. Many people have vision problems, some hereditary, while others come with increasing age. Myopia or nearsightedness, hyperopia or far sightedness, astigmatism, and low vision are a few main vision problems people can have. After an eye exam, a prescription from the eye doctor will be given for the correct type of glasses or contact lenses. However, this Rx may be difficult for a lot of people to understand, as the prescription generally contains many different numbers and abbreviations.
The abbreviation Rx stands for prescription. With an eyeglass prescription, there are various different parts to understand. An eyeglasses prescription will include the refractive power the glasses must be made to so the glasses correct whatever the vision problem is. There are many medical abbreviations and terms that may be written on eyeglass prescriptions.
D.V. on a prescription will stand for “distance vision”, meaning the part that focuses on improving a person’s far vision. For bifocals, the D.V. prescription will be what is on the top segment of the glasses. N.V. means “near vision”, this is the script that improves a person’s close-up sight, for reading or writing. For bifocals, this prescription will be for the bottom of the lens. The abbreviation O.D. stands for Oculus Dexter, which is Latin for “right eye”. O.S. stands for Oculum Sinister, which is Latin for “left eye”, and O.U. which stands for Oculus Uterque meaning “both eyes” or the “same Rx in both eyes”. Some eye doctors and ophthalmologists will just say left or right instead of using these terms.
In general terms, your eyesight is determined by the number on the prescription. The farther from the number zero, the worse the eyesight is. If there is a plus sign, then the vision is farsighted, a minus, the vision is nearsighted. These numbers are called the diopters, which is how the focusing power is measured. On some prescriptions, the word diopter may be abbreviated with the letter D.
Those who have astigmatism will have three different numbers listed on their eyeglasses prescription. These will be S, C, and Axis.
The abbreviation S refers to the spherical part of a person’s prescription. This is the degree that the person is near or farsighted. The C is the cylinder, which can be either a positive or a negative number. It will indicate in diopters how bad the astigmatism is. When the number is bigger, the astigmatism is worse.
There are two areas of an eyeglass Rx that may usually be left blank. The first is prism. Prism means the displacement of an image that comes through a lens. One condition this is used to treat is a muscular imbalance that can cause an error to occur in the eye orientation. Base is the other area usually left empty, as this refers to the direction the prism displacement is.
It is important to understand what your eye prescription means so you can carefully monitor your vision health. Talk to your eye doctor to help better understand what your Rx means.