Qurrah

How to read your eyeglasses prescription

The short answer

An eyeglasses prescription lists each eye separately (OD or R is the right eye, OS or L the left). SPH is the main lens power: minus for short-sightedness, plus for long-sightedness. CYL and AXIS correct astigmatism. ADD is extra reading power, usually needed from around age 40. PD is the distance between your pupils in millimetres, used to centre the lenses. No ADD means single-vision lenses; with an ADD you can choose progressives or separate reading glasses.

What the abbreviations mean

Most prescriptions are a small table with a row for each eye and a column for each value:

  • OD or R: right eye. OS or L: left eye. OU: both eyes.
  • SPH (sphere): the main power, in dioptres. A minus number such as −1.75 corrects short-sightedness (myopia), where distant things look blurry. A plus number such as +1.50 corrects long-sightedness (hyperopia). The bigger the number, the stronger the lens.
  • CYL (cylinder): extra power that corrects astigmatism, where the eye focuses unevenly. If the box is empty or says DS or SPH, there's no astigmatism correction for that eye.
  • AXIS: a number from 0 to 180 that tells the lab which direction to set the cylinder. It only appears with a CYL value and is an angle, not a strength.
  • ADD (addition): extra plus power for close-up work, added on top of your distance power. It's usually the same for both eyes.
  • Prism: less common. It helps with eye alignment and is written with a direction (BU, BD, BI or BO).

An example, line by line

Here's a typical prescription:

  • Right (OD): SPH −2.00, CYL −0.75, AXIS 180
  • Left (OS): SPH −1.50, CYL −0.50, AXIS 170
  • ADD: +1.50

Both eyes are short-sighted, the right a little more than the left, with mild astigmatism in both. The ADD of +1.50 means this person also needs extra power for reading, so progressive lenses or a separate pair of reading glasses would suit them.

Distance and near rows on Egyptian prescriptions

Many prescriptions written in Egypt have two rows for each eye, labelled Far (بعيد) and Near (قريب), instead of an ADD box. The near row is the distance power plus the reading addition. For example, if the distance SPH is −2.00 and the near SPH is −0.50, the ADD is +1.50.

When you order on Qurrah you can type your values in, upload a photo of your prescription, scan it with our AI camera, or pick a prescription saved to your account.

What is PD and how do you measure it?

PD (pupillary distance) is the distance between the centres of your pupils in millimetres, usually between 54 and 74 mm for adults. The lab uses it to place the optical centre of each lens in front of each pupil. It may be written as one number (63) or as two, one per eye (31.5/31.5). With an ADD you may also see a near PD a few millimetres smaller.

If PD isn't on your prescription, ask your optometrist or measure it yourself: stand about 20 cm from a mirror and hold a millimetre ruler flat against your brow. Close your right eye and line up zero with the centre of your left pupil, then open your right eye, close your left, and read the number at the centre of your right pupil. Repeat a few times and use the average. For progressive lenses, a PD measured by a professional is best.

Single-vision vs progressive lenses

Single-vision lenses have one power across the whole lens, for distance, for reading or for screen work. They're what most people wear, and the right choice when your prescription has no ADD.

Progressive lenses are for people with an ADD, usually from their 40s, when focusing up close gets harder (presbyopia). The power changes gradually from the top of the lens (distance) through the middle (arm's length, like a computer screen) to the bottom (reading), with no visible line. Most people need a few days to a couple of weeks to get used to looking through the right part of the lens, and progressives need a frame deep enough to fit all three zones.

If you'd rather not wear progressives, separate reading glasses are a simple alternative.

Choosing lens material and coatings

Once you know your prescription, choose the lens. Stronger prescriptions, roughly ±4.00 or more, look thinner and lighter in high-index lenses. You can also add blue-light filtering, or photochromic lenses that darken in the sun. Our lens guide explains each option.

How often should you get your eyes tested?

Prescriptions change over time, so most eye care professionals recommend an eye exam every one to two years, or sooner if your vision changes, you get frequent headaches or you find yourself squinting. Children and people with conditions such as diabetes may need more frequent checks. This guide helps you read a prescription; it doesn't replace an eye exam.

Ordering glasses with your prescription on Qurrah

Choose a frame, select single-vision, progressive or non-prescription lenses, and add your prescription for each eye. Not sure which frame suits you? Take our AI style quiz for suggestions. Already have a frame you love? With Reglaze, a courier picks up your glasses, we fit new lenses with your new prescription, and bring them back to you.

Frequently asked questions

What does a minus number on my prescription mean?

A minus SPH means you're short-sighted: you see close things clearly and distant things blurry. A plus SPH means you're long-sighted.

Is −2.00 a strong prescription?

It's mild to moderate. As a rough guide, up to about ±2.00 is mild, ±2.25 to ±5.00 is moderate, and anything higher is strong. Strong prescriptions benefit from high-index lenses and smaller frames.

What happens if my PD is wrong?

Small errors usually go unnoticed with weak prescriptions, but with stronger powers or progressive lenses a wrong PD can cause eye strain or blurry vision. Measure carefully, or ask your optometrist.

Can I use my glasses prescription for contact lenses?

No. Contact lenses need their own prescription with a base curve and diameter, and the power can differ from your glasses. Our contact lenses guide explains the difference.

Do I have to get progressive lenses if my prescription has an ADD?

No. An ADD means you need extra power for close work. Progressives give you distance and reading in one pair, but separate reading glasses also work. Talk to your optometrist about what fits your daily routine.