Demystifying Eye Prescriptions: Everything You Need to Know
As we age, it is common to experience deteriorating vision. And a visit to the optometrist reveals that you may need glasses, but the technical jargon on the prescription can be overwhelming. Eye prescriptions can leave you feeling confused, but fret not – we have got you covered. Here is everything you need to know about eye prescriptions:
The Basics of Eye Prescriptions
An eye prescription is a written document from an eye doctor or optometrist that outlines specifications for correcting vision. It includes information about the strength of lenses required, the type of lenses needed, and other relevant details. The prescription will often contain many numbers like -2.5 or +0.5, but what do they mean?
The prescription includes a series of abbreviations, often abbreviated as OD and OS, which refer to the right and left eye respectively. OD stands for the Latin term “oculus dexter” (right eye), while OS corresponds to “oculus sinister” (left eye). If you have eyeglasses with bifocal or progressive lenses, these abbreviations can be much longer.
What Do the Numbers and Abbreviations on an Eye Prescription Mean?
The strength of the lenses required for each eye is indicated by a series of numbers, measured in diopters (D), typically in increments of 0.25. The number may have a + or – sign in front of it. The plus sign (+) indicates farsightedness (hyperopia), while the minus sign (-) stands for nearsightedness (myopia).
For example, a prescription of -1.5 means that you are nearsighted, and the number indicates the degree of myopia in your eyes. On the other hand, +2.5 indicates that you are farsighted, and the number indicates the degree of hyperopia.
In addition to the strength of lenses, the prescription also specifies the type of lens needed—single vision, bifocal, or progressive. Single vision lenses help with near or distance vision, bifocal lenses contain two distinct prescriptions, which help with near and far vision, and progressive lenses contain three prescriptions, adjusting for near, far, and intermediate distances.
Interpreting Additional Terminology on Eye Prescriptions
The eye prescription may also include other technical terms, such as cylinder (CYL) and axis. The cylinder measures the level of astigmatism, which results in blurred vision. Astigmatism is an imperfection in the curvature of your eye, which then requires a special type of lens. The axis denotes the angle position of the cylinder, indicating the direction in which the astigmatism is angled.
The prescription may also indicate the pupillary distance (PD), which is the distance between the pupils’ centres measured in millimetres (mm). The PD measurement is essential for accurately positioning the optical centre of the lens. In most cases, your PD measurement is taken during an eye exam.
Conclusion
Getting a new pair of eyeglasses can be a daunting experience, especially when you’re trying to decipher your eye prescription. It’s important to understand the basics of what the numbers and abbreviations mean. Keep in mind that your optometrist or ophthalmologist would be happy to explain anything you don’t understand and help you select the lenses and frames that are best for you. With this guide on eye prescriptions, you’ll be well-equipped to make informed decisions about your eyewear.
