The process of acquiring a new pair of prescription glasses begins with a recent and comprehensive eye examination. A valid prescription is a medical document precisely detailing the specifications required to correct your vision, serving as the blueprint for your new lenses. Turning this document into a finished product involves understanding the vision correction details, choosing the physical components of the eyewear, and ensuring accurate measurements are applied during the ordering process.
Securing and Interpreting Your Eye Prescription
Securing a current prescription from an eye care professional, such as an optometrist or ophthalmologist, is the first step for obtaining new glasses. This document contains a series of standardized abbreviations and numbers that describe the exact lens power needed for each eye. The terms OD (Oculus Dexter) and OS (Oculus Sinister) refer to your right eye and left eye, respectively, ensuring the correct correction is applied to the appropriate lens.
The core of the prescription is the SPH (Sphere) value, which indicates the main lens power required to correct nearsightedness or farsightedness. A minus sign (-) next to the SPH value signifies correction for nearsightedness, or myopia, while a plus sign (+) denotes correction for farsightedness, or hyperopia. For people with astigmatism, the prescription will also feature a CYL (Cylinder) power and an AXIS measurement.
The CYL value specifies the additional lens power necessary to correct the irregular curvature of the cornea associated with astigmatism. This correction must be oriented at a specific angle, which is indicated by the AXIS number, a value ranging from 1 to 180 degrees. If you require multifocal lenses, such as bifocals or progressives, an ADD (Addition) power is included, representing the magnifying power needed for near vision tasks like reading. This ADD power is typically applied to both eyes equally and is combined with the distance correction to create the lens for close work.
Selecting Frame Styles and Lens Materials
After understanding the prescription, the next step involves selecting the physical components that will hold the corrective lenses. Frame choices generally fall into three categories: full-rim, which completely encircles the lens for maximum durability; semi-rimless, which features a frame only along the top of the lens; and rimless, where the lenses are connected only by the bridge and temples for a subtle, lightweight look. The frame material also impacts comfort and longevity, with metal options like titanium and stainless steel offering a sleek, durable, and often lighter feel.
Acetate, a plant-based plastic, provides a wider array of color and pattern options and is known for its flexibility and hypoallergenic properties. For moderate prescriptions and active lifestyles, polycarbonate or Trivex lenses are recommended because they are highly impact-resistant and shatterproof.
Individuals with stronger prescriptions often benefit from high-index plastic lenses, which are designed to be significantly thinner and lighter than standard plastic. All lenses should be enhanced with protective coatings. An Anti-Reflective (AR) coating reduces glare from light sources and improves the clarity of vision, while a scratch-resistant hard coat extends the lens lifespan.
Ordering Procedures and Essential Measurements
The ordering process requires providing precise measurements to ensure the optical center of the lens aligns perfectly with your pupils. The most important measurement is the Pupillary Distance (PD), which is the distance in millimeters between the centers of your pupils. The PD ensures that the point of maximum clarity on the lens is directly in front of your eye, and an incorrect PD can cause eye strain and discomfort.
When ordering from a physical optical store, a staff member will professionally measure your PD using a specialized instrument called a pupillometer. If ordering glasses online, you will likely need to measure the PD yourself. The PD may be provided as a single number, indicating the total distance, or as a dual PD, which provides a separate measurement for each eye from the center of the nose bridge.
For those purchasing progressive lenses, an additional measurement called segment height is required, which determines where the reading portion of the lens begins vertically. This measurement is generally taken with the chosen frame already on your face to ensure accuracy. Once all prescription details and measurements are submitted, the lenses are custom-ground and inserted into the chosen frames, typically requiring a turnaround time of one to two weeks before the glasses are ready for final fitting and adjustment.