How to Read Eye Prescriptions like an Expert

Protect your vision

Protect your vision

It’s becoming increasingly important to know how to read eye prescriptions. After all, e-commerce eyewear brands are more popular than ever, and there are plenty of opportunities to purchase a wide variety of glasses online – from sunglasses and prescription glasses to blue light glasses and reading glasses.

At first glance, it can be hard to understand how an optical prescription works. But with a few key insights, you can quickly get to grips with the ins and outs of eye prescriptions, giving you the chance to explore a wide range of glasses without the need to consult an optician.

Here’s our snapshot guide on how to read eye prescriptions like a pro:

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Glasses prescriptions 101

Glasses prescriptions 101

Prescriptions for eyeglasses are typically represented by a series of numbers listed under different headings: OS, OD and OU.

These refer to Latin acronyms:

- OS: oculus sinister, referring to the left eye

- OD: oculus dextrus, for the right eye

- OU: oculus uterque, both eyes.

Although these are still the most common terms used for prescription glasses, some opticians have started to modernize their prescriptions with the use of RE, for the right eye and LE for the left eye.

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Understanding your eye prescription

Understanding your eye prescription

These are the three elements that are important in an eye prescription:

S x C x Axis

(for example: O.D -2.50 -0.75 x173 / O.S -3.00 -1.00 x004).

- SPH or SPH: measures the degree of nearsightedness or farsightedness

- C or CYL: indicates the amount of lens power or degree of astigmatism, and it can be negative or positive. The bigger the number, the stronger the astigmatism

- Axis: a number between 0 and 180 degrees that reveals the orientation of the astigmatism, in order to know where the curvature is taking place

Astigmatism, the degree measured in CYL, is often caused by a cornea that is shaped like a football instead of being perfectly rounded. It also means that there are a few more things to take into consideration when reading your prescription.

Our prescription range

Our prescription range

Range of lenses: We can accommodate any eye prescription ranging from +6.00 to -8.00, and Cylinder (C or CYL) from +4.00 to -4.00.

Please keep in mind that the sum of sphere and cylinder metrics can only reach a maximum of -8 or +6.

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FAQS

You’ll just need a ruler in millimeters and a mirror.

Here’s how you can easily measure your pupillary distance:

1. Place yourself in front of a mirror. Ideally at 20 cm away (8 inches).
2. Once in front of the mirror, look straight ahead and place the ruler on the bridge of your nose.
3. With one hand, make sure that the ruler starts (the zero end) in your right pupil.
4. Measure the distance between your right pupil and your left pupil.
5. The number will be your PD, also known as pupillary distance.

Prescription for bifocal or progressive lenses correct the vision at the same time for far and for near distances; it's two prescriptions in one.

We are not producing progressive lenses, but we can offer to prepare one of the prescriptions you have: either to see far on the street, or to see near for reading.

For far distances: introduce the part of prescription without ADD (Sphere, Cylinder, and Axis)

For near distances: sum Sphere + ADD, and introduce Cylinder and Axis.

The ADD appears in the bottom of a prescription when the additional power needed is actually the same for both eyes.

A prescription for general use is a type of common prescription, where the Axis, Cylinder, and Sphere are determined without any type of addition.

Prescriptions that help to improve the sight at close distances will have an ADD that will be integrated with the Sphere. The Axis and Cylinder will remain the same.

For example, if you have ADD +2 then:

Right Eye (OD)

SPH: -1.00 + 2.00 = +1.00

CYL: -0.50

AXIS: 180

Left Eye (OI)

SPH: -1.50 + 2.00= +0.50

CYL: -0.50

AXIS: 70