PD 63/60 frequently appears on eyeglass prescriptions, causing confusion for people who encounter it outside of a clinical setting. This notation is a concise, coded instruction that holds significant information for the manufacture of corrective lenses. Understanding this term requires breaking down the abbreviation and the numerical values to grasp its full context. The abbreviation “PD” stands for Pupillary Distance, which is the measurement, expressed in millimeters, between the centers of the pupils of the eyes.
Deconstructing the Designation: What PD 63/60 Signifies
The number 63 represents the Distance Pupillary Distance, which is the measurement used when the eyes are focused on an object far away. The second number, 60, indicates the Near Pupillary Distance, measured while the eyes are converged, or focused on something up close, such as reading material. This near measurement is typically 3 to 4 millimeters less than the distance measurement because the eyes naturally turn slightly inward when focusing on nearby objects. When a prescription lists two separate values, such as 63/60, it provides a precise instruction for customizing the lens focal point for both distance and reading tasks.
The Core Mandates of the Measurement
The primary function of the PD measurement is to ensure the optical center of the corrective lens aligns directly with the center of the pupil. For a prescription with a significant power, even a small error in this alignment can introduce unwanted prismatic effects. Misalignment causes the light entering the eye to bend incorrectly, which can lead to visual discomfort, eye strain, and headaches. The difference between the distance and near PD is particularly important when manufacturing multifocal lenses, like bifocals or progressive lenses. Accurate PD values are therefore a fundamental requirement for achieving optimal visual clarity and comfort with corrective eyewear, as they guide the precise positioning of the near segment.
Scope of Application and Current Relevance
The PD measurement is a universal requirement for nearly all types of prescription eyewear, including single-vision lenses, bifocals, and progressive lenses. This measurement applies to anyone seeking to purchase glasses for vision correction, regardless of the prescription’s strength. While an average adult PD is around 63 millimeters, the exact measurement is unique to each individual. The relevance of the PD 63/60 notation has grown significantly with the rise of online purchasing for prescription eyewear. Consequently, the explicit inclusion of the distance and near PD on a prescription is important for consumers seeking choice and convenience in acquiring their corrective lenses.