How to read your eye prescription (SPH, CYL, ADD)

Your eye prescription looks like a table of abbreviations and numbers. Once you know what each one means, it’s simple, and it helps you choose the right lenses with confidence. Here’s a plain-English guide.

Right eye and left eye: RE/LE or OD/OS

Every prescription lists each eye separately. You’ll see RE / LE (right eye, left eye) or the Latin OD / OS (oculus dexter = right, oculus sinister = left). Sometimes you’ll also see OU, which means both eyes.

The terms on your prescription

Term	What it means
SPH (sphere)	The main lens power, in dioptres. Minus (–) corrects short-sight, plus (+) corrects long-sight.
CYL (cylinder)	Extra power to correct astigmatism. Blank or “DS” means you don’t need any.
AXIS	The angle of the astigmatism correction, from 0 to 180 degrees. It only appears with CYL.
ADD	Additional reading power added to the bottom of a progressive or bifocal lens.
PD	Pupillary distance: the gap between your pupils in mm, used to centre the lenses.
PRISM	Rare. Corrects eye alignment issues; if you have it, mention it when ordering.

What minus and plus powers mean

• Minus (–) SPH: short-sight (myopia). You see near things clearly, far things are blurry. –0.25 to –3.00 is mild to moderate; higher numbers are stronger.
• Plus (+) SPH: long-sight (hyperopia). Near things are harder to focus on.
• Powers go in steps of 0.25. The bigger the number, the stronger the lens.

Higher powers are where high-index (thinner) lenses help, so your lenses don’t look thick at the edges.

What astigmatism (CYL and AXIS) means

Astigmatism means the front of your eye is shaped more like a rugby ball than a football, so light focuses unevenly. It’s very common and easily corrected. The CYL number tells us how much correction you need and the AXIS tells us which direction. Both have to be exact, so always copy them carefully.

A worked example

	SPH	CYL	AXIS	ADD
RE	–2.00	–0.75	180	+1.50
LE	–1.75	–	–	+1.50

This means mild short-sight in both eyes, a little astigmatism in the right eye, and +1.50 of extra reading power. Because there’s an ADD, this person would usually choose progressive lenses. Without the ADD, they’d need single vision.

What is PD and how do I find it?

PD (pupillary distance) is usually between 54 and 74 mm for adults. It’s often written on the prescription; if it isn’t, don’t worry. We can measure it from your current glasses during doorstep lens replacement, or verify it with you before making your lenses.

Is a glasses prescription the same as a contact lens prescription?

No. Contact lenses sit on the eye, so the powers and measurements differ. Use your spectacle prescription for glasses.

How old can my prescription be?

If it’s within about one to two years and you see clearly with it, it’s usually fine to use. Get a fresh eye test if you’re squinting, getting headaches, or your current glasses no longer feel sharp. If your power has changed, you can usually keep your frame and just change the lenses. See power changed? Keep your frame.

Ready to order?

Enter your prescription when you choose your lenses, or send a photo of it on WhatsApp and our lens experts will check it for you. Want new frames too? Browse eyeglasses.