When you decide to purchase a VR prescription lens online. The first thing you should do is to confirm your prescription. Although reading a prescription may appear to be a dark art, our tips below will assist you in navigating and comprehending your prescription information.
Here's an example of a prescription. Prescriptions differ, so yours might not look the same.
Terms Required for VR Prescription Lens
1. SPH (Spherical)
The spherical (SPH) determines if you have hypermetropia (plus sign) or myopia (minus sign). The number indicates the strength of the lens you need. A smaller number signifies a milder condition. PL stands for plano and implies that the eye has no refractive error.
2. CYL (Cylinder)
The abbreviation CYL refers to cylinder and indicates the seriousness of astigmatism. The axis depicts the angle at which your lenses' cylindrical power must be set to correct it. You may notice DS in the column, which stands for diopter sphere and indicates that you do not have astigmatism.
3. AXS (Axis)
Axis is a number from 1 to 180. If your doctor has included cylinder power, there will also be an axis value to indicate positioning. Axis is measured in degrees and refers to where the astigmatism is located on the cornea.
OD is an abbreviation for “oculus dexter” which is Latin for “right eye.”
OS is an abbreviation for “oculus sinister” which is Latin for “left eye.”
Terms Not Required for VR Prescription Lens
1. PD (Pupillary Distance)
The distance between your pupils centered is measured by the Pupillary Distance (PD). This measurement must be as accurate as possible because it determines where you are looking through the lens of your glasses or VR insert. The PD of an average adult is 54mm to 74mm whereas children’s PD falls between 43mm to 58mm.
2. Add (Near add and intermediate add)
Add is used in multifocal lenses to indicate the additional magnifying power for the bottom part of the lens. These terms are much more usual in people over the age of 40 and pertain to the extra correction you might need to focus on short ranges. The intermediate add refers to the extra strength of lenses you would need to bring a mid-range distance into focus. A good illustration of this is the distance between you and the computer screen you're staring at. Meanwhile, the near add is typically used for close activities like reading. To get an accurate near or intermediate prescription, this number is applied to the spherical error portion of the prescription. If needed, the intermediate add can be written in by hand if the prescription does not have a section for it.
3. Prism (Prismatic power)
Prism only appears on a low number of prescriptions. It’s used when your doctor feels that compensation for eye alignment is necessary. The prismatic power, also known as prism, is intended to correct binocular vision difficulties in which both eyes have a hard time working together. The strength of the correction is indicated in the prism column, and the base column specifies in which direction the prism acts. The back vertex distance (BVD) is the measurement between the front of your eye and the lens of your glasses in millimeters. This distance, which might affect a lens's effective strength, is normally reserved for prescriptions with higher strengths.