What Do These Numbers Mean? – Understanding An Eye Prescription

If you wear contact lenses or prescription glasses, you’ve likely seen the numbers and abbreviations on your prescription form. They might seem like a random collection of letters and figures, but these details are important for ensuring your glasses match your vision needs. Here’s what the numbers mean, why regular eye tests are important, and how to choose the right pair of glasses.

What do the numbers mean?

OD and OS stand for “oculus dexter” (right eye) and “oculus sinister” (left eye). If both eyes have the same prescription, you might see “OU”, which means “oculus uterque”, or both eyes.

SPH (sphere) indicates the degree of nearsightedness or farsightedness in diopters, which measure the strength of the lens you need. A negative (-) value means you’re nearsighted (struggle to see distant objects clearly), and a positive (+) value indicates farsightedness (nearby objects appear blurry).

CYL (cylinder) values represent the additional lens power required to correct astigmatism. No number here means you don’t have astigmatism. (If you have astigmatism, your eyes aren’t perfectly spherical.)

Axis specifies the angle (in degrees) at which the cylindrical correction is applied to correct the distortion, ranging from 0 to 180 degrees.

If your prescription includes an ADD value, it’s for multifocal lenses, such as progressives or bifocals. This number helps correct presbyopia, the age-related difficulty in focusing on close objects.

In some cases, a prism correction addresses issues with eye alignment, such as double vision. The base indicates the direction of the prism correction.

Why should I get a regular eye test?

Your vision is constantly changing, and regular eye exams are important for maintaining clear sight and overall eye health.

Even small changes in your vision can impact daily tasks: reading, driving, and working on a computer to cite just three common examples. An updated prescription means your glasses give the best possible clarity and comfort.

Eye tests are also helping for detecting eye diseases, such as glaucoma, cataracts, and macular degeneration, which can develop without obvious symptoms.

Your eyes can reveal signs about other health issues, including diabetes, high blood pressure, and even some neurological conditions. An eye test acts as a window into your overall health, making it an important part of preventative care.

For children, regular eye exams are important for detecting vision problems that can affect learning and development, such as myopia (nearsightedness) or amblyopia. These are often correctable if caught early.

Protecting your eyes if you have diabetes

Proactive management of your eye health can help prevent or minimize complications.

Keeping your blood sugar levels within the target range is the most effective way at reducing the risk.

High blood pressure and cholesterol can exacerbate eye damage, so healthy levels help.

Regular eye tests (at least one per year) can help manage your eye health. Quitting smoking is also a good idea, as smoking increases the risk of diabetes-related complications.

If you notice any changes in your vision (blurriness, floaters, or flashes of light), consult an eye doctor.

A range of styles available

Prescription glasses aren’t just about function. Many people enjoy them to reflect their style and personality. There’s a huge variety in designs, materials, and features.

There are round frames, square frames, cat-eye frames, and aviators.

Modern glasses come in a variety of materials, including metal, acetate, titanium, and eco-friendly frames.

From high-end designers like Ray-Ban, Prada, and Oakley to more affordable, stylish lenses, there are options for various budgets and aesthetics.

Additional lens features

Advancements in lens technology mean you can customize your glasses.

There are photochromic lenses, also known as Transitions lenses, which adapt to changing light conditions, effectively doubling as sunglasses when you’re outdoors.

Anti-reflective coatings can minimize glare, which can be useful for nighttime drives or computer work.

Scratch-resistant coatings help make lenses more durable.

As well as these features, there are specific types of prescription lenses, including reading glasses, progressive lenses (lenses that transition between near and far vision), and sports glasses designed for performance.

Sports glasses offer better protection, durability, and additional performance features. They’re often made from polycarbonate, a highly impact-resistant material to withstand occasional bumps, hits, or falls. This is important in sports like basketball, soccer, and hockey. The lenses are shatterproof to minimize risk of injury from flying debris or accidents, and they often feature wraparound frames to protect the eyes from all angles.

Sports lenses are sometimes tinted for specific environments. Yellow or amber lenses enhance contrast in low light, while polarized lenses reduce glare and are often used for water and snow sports.

When should I schedule my next eye test?

Generally speaking, children should have a test every 1-2 years, while adults should have a test every 2 years (or annually if you wear glasses or have a condition like diabetes). Seniors should have a test annually.

Schedule a test sooner if you notice a change in your vision, such as blurriness or difficulty seeing at night, or headaches.

Last word

Maintaining regular eye tests and choosing the right prescription glasses are important for clear vision and eye health. Take proactive steps to improve your vision, confidence, and quality of life, by scheduling regular eye tests.