The measurement of the proper PD enables the center of the lens to align with the center of the pupil.The first abbreviations you will notice are the letters OD and OS. These are derived from Latin for Oculus Dexter (OD) for right eye and Oculus Sinister (OS) for left eye. Occasionally, there may be the abbreviation OU, oculus uterque, for both eyes. The PD number is very important for properly fitting lenses and is required for optimum visual comfort and performance. Once you reach adulthood, this number does not change. The pupillary distance, or PD, is the distance between the centers of each pupil (black hole). It will also most often be the same number for both eyes.
#OD OS WHICH IS RIGHT AND LEFT PLUS#
The add number is always a plus power, even if it is not preceded by a plus sign on your prescription. The magnifying power increases as your eye moves down the corridor of the lens in the case of multifocal lenses. These numbers refer to additional (magnifying) power needed to correct presbyopia, or the inability to see close up that happens as we age. The need for correcting eye alignment is uncommon, so only a small number of eyeglass prescriptions include prism. Prismatic powers are prescribed to help with eye alignment problems (vertical and horizontal). The prism numbers represent the amount of prismatic power needed for your eyes. If the cylinder section on your prescription is blank, then you will not have an axis number as the prescription is spherical. The idea is to neutralize the difference in power in the eye with the power in the lens. Axis numbers are measured in angle degrees ranging from 1 to 180.
![od os which is right and left od os which is right and left](http://webeye.ophth.uiowa.edu/eyeforum/cases-i/case232/Fig1c-lrg.jpg)
The axis number describes the position of the astigmatism in your eye. This number shows the direction the eye doctor needs to position any cylindrical power in your lenses (required for astigmatism only). If this column is blank, then you have no astigmatism or it is too slight to need correction. The cylinder number is most commonly preceded by a minus sign and represents the difference in power that exists as you measure how the eye focuses light. Astigmatism is a condition where the eye does not focus light evenly onto the retina, causing images to blur or stretch. This number refers to the amount of astigmatism in your eyes. If there is a minus sign (-) in front of the number, it means you are nearsighted and have more trouble seeing at a distance. If there is a plus sign (+) in front of the number, it means you are farsighted and have more trouble seeing things close up. Typically, the farther away the number is from zero, the more vision correction you need. These numbers are measured in diopters (D) and represent the amount of lens power needed to correct your vision. While using the Latin abbreviations is traditional for eyeglass prescriptions, some doctors have started modernizing their prescriptions by using RE (right eye) and LE (left eye). Sometimes a prescription will include the letters “OU,” oculus unitas, meaning both eyes. That’s why we put together the following guide to help you dissect your eyeglass prescription.įirst, notice the letters “OD” and “OS” on your eyeglass prescription. These are Latin abbreviations for the terms oculus dextrus, meaning right eye, and oculus sinister, meaning left eye. With so many letters and numbers (and not to mention plus signs and minus signs), it can be confusing.
![od os which is right and left od os which is right and left](https://webeye.ophth.uiowa.edu/eyeforum/cases-i/case200/Fig-2.jpg)
But have you ever tried reading an eyeglass prescription from your optometrist or ophthalmologist? Not so easy. Even if your doctor is notorious for scribbled handwriting, more often than not you can read what medication he or she has prescribed. When you go to the doctor for an illness, it’s pretty easy to read the prescription written for you.