Understanding Your Eye Prescription: A Simple Guide

You’ve just had an eye exam, and now you’re looking at a slip of paper filled with numbers, abbreviations, and symbols that might as well be a secret code. Don’t worry — at Iftikhar Optical, we explain prescriptions to customers every day, and by the end of this guide, you’ll understand exactly what yours means.

What Does an Eye Prescription Look Like?

A typical eye prescription looks something like this:

	SPH	CYL	AXIS	ADD
OD (Right Eye)	-2.50	-0.75	180	+1.50
OS (Left Eye)	-3.00	-0.50	175	+1.50

Let’s break down each element:

OD and OS: Which Eye Is Which?

OD stands for “Oculus Dexter” (Latin for right eye). OS stands for “Oculus Sinister” (left eye). Some modern prescriptions simply use R and L. The right eye is always listed first.

SPH (Sphere): Your Main Prescription

The SPH value indicates the lens power needed to correct your vision:

• Negative (-) numbers mean you’re nearsighted (myopic) — you can see close objects clearly but distant objects are blurry
• Positive (+) numbers mean you’re farsighted (hyperopic) — distant objects may be clearer than close ones
• The further from zero, the stronger the correction needed

Common ranges:

• Mild: -0.25 to -3.00 (or +0.25 to +3.00)
• Moderate: -3.25 to -6.00
• High: Beyond -6.00 (consider high-index lenses for thinner, lighter glasses)

CYL (Cylinder): Astigmatism Correction

Not everyone has this on their prescription. CYL corrects astigmatism — a condition where your cornea is shaped more like a rugby ball than a basketball, causing blurred or distorted vision at certain angles.

If your prescription has CYL values, don’t worry — astigmatism is extremely common and easily corrected with properly made lenses.

AXIS: Direction of Astigmatism

If you have a CYL value, you’ll also have an AXIS value (1-180 degrees). This tells the lab the exact angle at which to position the astigmatism correction in your lens. Think of it as the compass direction for your lens.

ADD (Addition): Reading Power

The ADD value appears on prescriptions for people who need multifocal lenses (usually age 40+). It indicates the extra magnifying power needed for reading and close-up work, and it’s always a positive number.

If you have an ADD value, you’ll need either bifocal or progressive lenses. At Iftikhar Optical, bifocals are Rs 1,500 extra and progressives are Rs 3,000 extra.

PD (Pupillary Distance)

PD is the distance in millimeters between the centers of your pupils. This ensures the optical centers of your lenses align with your eyes for the clearest vision. Average PD for adults is 54-74mm.

Some prescriptions include PD; others don’t. We measure PD free of charge at our Lahore store.

Prism (Less Common)

Some prescriptions include a prism correction for eye alignment issues. The prism value is measured in prism diopters with a direction (base up, down, in, or out). This is less common and is usually prescribed by an ophthalmologist.

How Long Is My Prescription Valid?

In Pakistan, eye prescriptions are generally considered valid for 1-2 years. However, you should get a new eye test if:

• You experience headaches or eye strain
• Objects at any distance become blurry
• You squint frequently
• You hold your phone or books at unusual distances
• It’s been more than 2 years since your last exam

Tips for Getting an Accurate Prescription

1. Get tested when rested: Eye fatigue from screen use can temporarily affect results
2. Bring your current glasses: The optician can compare your old and new prescriptions
3. Mention your lifestyle: Tell the optician about your screen time, driving habits, and hobbies
4. Be honest during the exam: If two options look similar, say so — don’t guess
5. Ask questions: A good optician (like ours at Iftikhar Optical!) will happily explain everything

Frequently Asked Questions

Can I use my prescription to buy glasses anywhere?

Yes! Your prescription belongs to you. You can use it at any optical store or online retailer. At Iftikhar Optical, we also accept prescriptions from other eye doctors.

Is a prescription from an optician the same as from an ophthalmologist?

For glasses purposes, yes — both can accurately determine your lens prescription. Ophthalmologists are medical doctors who can also diagnose and treat eye diseases.

Why does my prescription keep changing?

Prescriptions naturally change over time due to aging, lifestyle changes, or eye health conditions. Regular check-ups ensure you always have the most accurate correction.

Need an eye test? Iftikhar Optical offers free comprehensive eye testing at our Lahore store (H8RP+CMJ, Umar Din Rd, Wasanpura, Shad Bagh, Lahore, Punjab). No appointment needed — walk in Mon-Sat 10AM-9PM or Sun 12PM-8PM. Call +92 304 957 0000 or WhatsApp us.