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Reading a prescription from your eye doctor can be difficult, even under the most favorable circumstances. Optical professionals’ handwriting can often be challenging to decipher, and they may simplify their instructions, expecting their trained counterparts to understand them.
When shopping for eyeglasses online, it is unlikely that you possess the expertise of an optical professional. Moreover, if you are browsing Phillips Safety you are likely seeking safety glasses that are suitable for your intended application, which may lead to concerns about correctly communicating your prescription.
Whether you are shopping for prescription safety glasses for laser work, welding, radiation, glassworking, or general prescription safety glasses, it is crucial to ensure that your prescription is accurate. If you are unsure about the information listed on your prescription or how to enter it into our online forms, the following information may be helpful.
The prescription designates your right and left eyes as OD (right eye) and OS (left eye), respectively. If you are uncertain about the proper designation, remember that the OD (right eye) always appears first. In addition, each prescription contains three correction categories for each eye, including Sphere (SPH), Cylinder (CYL), and Axis. It is possible that your prescription may include all or some of these categories.
The Sphere category corrects nearsightedness or farsightedness and is indicated by a positive or negative value in increments of 0.25. Your prescription for each eye may contain, for example, values such as +1.25, 0.75, -2.00, or +3.50.
Cylinder and Axis are interdependent categories, meaning that you can’t have one without the other, although it is possible to have both for one eye and none for the other. Cylinder is expressed in the same manner as Sphere, with positive or negative values in increments of 0.25. On the other hand, Axis denotes the angle at which the cylinder is rotated, and it is measured in degrees from 0 to 180. While Sphere values remain constant irrespective of the lens’s orientation, Cylinder values differ with rotation, necessitating the prescription to specify the direction of rotation through the Axis category.
When reading your prescription, it is important to note that both sphere and cylinder measurements always have two numbers after the decimal place. Occasionally, eye doctors may forget to include the decimal point. In this case, it is safe to assume that the prescription has two numbers after the whole number. For instance, if your prescription is written as -250, it actually means -2.50. Similarly, if your prescription is written as -25, it means -0.25, and if it is written as +100, it means +1.00. Plus, if your doctor has written “SPH” in the cylinder section, it indicates that there is no cylinder correction required.
If you are getting a bifocal, the strength for a bifocal on a prescription is typically indicated below the Sphere, Cylinder, and Axis section. You may see it labeled as “ADD”, “BIFOCAL”, or “NEAR”, or it may not be labeled at all. Note that it is usually the same strength for both eyes, so some doctors only write it once instead of twice for each eye. Additionally, the strength is always positive.
The distance between the centers of your pupils is called pupil distance, which is measured in millimeters. Sometimes, it may not be included in the prescription, requiring you to measure it yourself. If it is written on the prescription, it is often abbreviated as PD.
The segment height is the measurement from the bottom of the lens to the top of the bifocal, which can either be a line on a lined bifocal or the start of the progressive corridor on a progressive bifocal. For lined bifocals, the segment height is usually estimated. For progressives, it is measured in millimeters from the bottom of the lens to the center of your pupil and can vary for every frame.
Phillips Safety understands that purchasing prescription safety glasses can be a complex process, which is why our team of trained professionals is readily available to guide you through the ordering process and ensure that you make an informed decision. If you need further assistance in filling out your prescription on our forms, don’t hesitate to contact us.
