Ordering reading glasses from a prescription can seem complicated, but it is straightforward once the key measurements are understood. Reading glasses provide magnification for close-up tasks, such as reading a book, sewing, or working on a computer screen. This magnification is necessary because the eye’s natural lens loses flexibility with age, a condition known as presbyopia, making it difficult to focus on near objects. By translating the data provided by your eye doctor into an order, you can ensure your new glasses offer clear and comfortable vision.
Deciphering the Reading Glasses Prescription
The first step in ordering is to understand the language of your eye prescription, which details the specific power required for each eye. Your prescription form will use the Latin abbreviations OD (Oculus Dexter) for the right eye and OS (Oculus Sinister) for the left eye. These terms distinguish between the two eyes and are typically found at the beginning of the horizontal rows containing your measurements.
The most important measurement for reading glasses is the ADD (Addition) power, which indicates the extra magnifying power needed for near vision tasks. This value is always positive and is usually the same for both eyes, correcting for presbyopia. This ADD power is combined with the Sphere (SPH) measurement, which represents your base refractive error, correcting for existing farsightedness (+) or nearsightedness (-).
For individuals who require correction for an irregularly shaped cornea, the prescription will also include Cylinder (CYL) and Axis values. The CYL number indicates the lens power needed to correct astigmatism, while the Axis specifies the orientation of this correction, measured in degrees from 1 to 180. While many simple, over-the-counter reading glasses do not include this astigmatism correction, it must be included if you are ordering custom prescription reading glasses. Your prescription provides all the necessary power values, but a measurement regarding the physical fit of the glasses is often not included.
Obtaining Your Pupillary Distance (PD) Measurement
The Pupillary Distance (PD) is a measurement of the space between the center of your pupils, usually expressed in millimeters. This number is vital because it ensures the optical center of the lenses aligns precisely with the center of your pupils. Proper alignment is necessary for the lenses to function as intended and to prevent eye strain. If the optical centers are misaligned, you may experience headaches or distorted vision, especially with stronger prescriptions.
For reading glasses, you need the Near PD, which is slightly different from the Distance PD used for driving or full-time glasses. This distinction matters because your eyes naturally converge, or turn inward, when focusing on close objects. As a result, the Near PD is typically 2 to 4 millimeters smaller than the Distance PD.
Since the PD is often omitted from the eye doctor’s prescription, you may need to obtain this number yourself. The most reliable method is to ask your eye care professional to provide the measurement, as they use specialized tools like a pupillometer. If this is not possible, you can measure it at home using a ruler and a mirror, or by using a friend to help. To calculate your Near PD from a Distance PD, you can generally subtract 3 millimeters from the total distance measurement.
Selecting Lenses and Placing the Order
Once you have your complete prescription data, including the necessary Near PD, the final step involves selecting the physical features of the glasses and submitting the order. You will first need to choose a venue for purchase. Online retailers offer convenience and potentially lower costs, while in-store opticians provide professional fitting and adjustments.
Next, select the lens type based on your primary activity. Single-vision readers are appropriate for consistent, fixed-distance tasks like reading a book. For those who frequently switch between reading and intermediate distances, such as viewing a computer screen, consider computer progressives. These are sometimes called “office lenses” and are designed specifically for the near and mid-range focal points common in a workspace.
The choice of lens material affects durability and weight. CR-39 plastic is a common, affordable option, and polycarbonate or high-index plastic offers thinner, lighter, and more impact-resistant lenses. You should also consider lens coatings to enhance visual comfort and longevity:
- An anti-reflective (AR) coating minimizes glare and reflections from overhead lighting and computer screens.
- Blue light filtering.
- Scratch-resistant coatings.
Finally, select a frame that fits comfortably, paying attention to the bridge width and temple length, as reading glasses are often worn for extended periods.