Yes, it is entirely possible to obtain single-vision glasses from a progressive lens prescription. Progressive lenses are a form of multifocal correction, designed to provide a seamless transition of power for viewing objects at far, intermediate, and near distances. This design eliminates the visible lines found in traditional bifocals. Single-vision glasses contain only one power across the entire surface of the lens, designed for a single, specific viewing distance. The comprehensive measurements taken for your progressive prescription contain all the necessary data points to calculate the power for dedicated single-vision lenses for any distance you need.
Understanding Progressive Prescription Components
A progressive prescription contains several specific measurements that define the various powers within the lens. The Sphere (SPH) value is the foundational power, indicating the main correction needed for nearsightedness (minus sign) or farsightedness (plus sign) at a distance. This number forms the basis for all other calculations.
In addition to the spherical power, the prescription may also list Cylinder (CYL) and Axis (AX), which correct for astigmatism, an imperfection in the curvature of the eye’s cornea or lens. The CYL value specifies the amount of power needed, while the AX value indicates the orientation or angle of the correction (measured in degrees from 1 to 180). These values remain constant regardless of the viewing distance.
The most differentiating component is the Near Addition (ADD) power. The ADD value represents the supplementary magnifying power, measured in diopters, that must be added to the SPH power to achieve clear near vision. This addition power is necessary due to presbyopia, the age-related hardening of the eye’s natural lens that impairs close focusing ability. The progressive lens achieves its multifocal function by gradually increasing the power from the distance SPH at the top to the full SPH plus ADD power at the bottom.
Calculating Single Vision Power from the Progressive Prescription
Converting a progressive prescription into a single-vision prescription is a straightforward process of algebraic addition. To create a dedicated single-vision lens for far distance, the distance portion of the progressive prescription is used directly. This means the SPH, CYL, and AX values are taken as written, and the ADD power is disregarded entirely.
To calculate the power for dedicated near-vision glasses (reading glasses), the full ADD power is algebraically combined with the SPH power. For example, if the distance SPH is -1.00 diopters and the ADD is +2.00 diopters, the new spherical power is +1.00 diopters (-1.00 + 2.00 = +1.00). The CYL and AX values remain unchanged, as astigmatism correction is required across all viewing distances.
This calculation provides the total refractive power needed for the typical reading distance (around 14 to 16 inches or 35 to 40 centimeters). The resulting single-vision lens will have this combined power uniformly across the entire surface, providing a wider and clearer field of view for close-up tasks than the narrow near-vision zone of a progressive lens.
Choosing the Best Single Vision Lens for Specific Tasks
Selecting the appropriate single-vision lens from your progressive prescription depends on the task and the required viewing distance. The full SPH plus ADD power, calculated as the near-vision prescription, is best suited for fine, close-up tasks like reading a book, sewing, or using a smartphone. These dedicated reading glasses offer the maximum magnification needed for short working distances.
For intermediate tasks, such as working at a desktop computer or viewing objects at arm’s length, the full reading power is often too strong. The typical computer working distance (about 20 to 30 inches) falls between the near and distance zones of the eye. To calculate the intermediate single-vision power, add approximately half of the ADD power to the SPH power.
For instance, if your ADD power is +2.00, an intermediate lens would use an addition of approximately +1.00 diopter. This SPH plus half-ADD calculation creates a lens optimized for the arm’s-length range of a computer monitor or a musical stand. While single-vision lenses sacrifice the convenience of a progressive lens, they provide a significantly wider and less distorted field of view for the chosen distance, enhancing comfort and visual clarity during prolonged, single-task activities.