When you get your eyes tested, your doctor hands you a prescription filled with numbers, abbreviations, plus (+) and minus (–) signs. But what do they actually mean? Let’s break it down so you can better understand your eye health.
Decoding Your Eye Prescription
After an eye exam, your optometrist or ophthalmologist will write a prescription for glasses or contact lenses. This prescription contains several abbreviations and measurements:
- O.D. (Oculus Dexter): Right eye
- O.S. (Oculus Sinister): Left eye
- O.U. (Oculus Uterque): Both eyes
- CYL (Cylinder): Correction for astigmatism
- AXIS: Direction of astigmatism correction
- DV (Distance Vision): Correction for seeing far objects
- NV (Near Vision): Correction for reading or close-up work
- ADD: Extra power for bifocal or multifocal lenses
The main number you’ll see is the diopters sphere (DS).
- A minus (–) sign means you are nearsighted (myopia).
- A plus (+) sign (or no sign) means you are farsighted (hyperopia).
- Higher numbers = stronger prescription.
For astigmatism, the CYL value also comes with a + or – sign. The higher this number, the more significant your astigmatism.
Glasses vs. Contact Lens Prescriptions
A glasses prescription is not the same as a contact lens prescription.
- Glasses sit about 12mm away from your eyes.
- Contact lenses sit directly on your eyes, so the measurements differ.
A contact lens prescription includes:
- Base Curve (BC): The curve of the lens that matches your eye shape (usually between 8–10).
- Diameter (DIA): Size of the lens (typically 13–15 mm).
- Lens Brand/Material: Recommended by your eye doctor.
- Expiration Date: Contact prescriptions usually last 1–2 years.
For multifocal contacts, you may also see:
- ADD Power: Labeled as low, medium, or high.
- D/N Labels: “D” for distance center, “N” for near center.
How Astigmatism Affects Vision
Astigmatism is a common condition where the eye’s surface is uneven, causing blurry or distorted vision.
- If your prescription has a CYL number, it means you have astigmatism.
- No CYL value means you either don’t have it or it’s too mild to correct.
What Does 20/20 Vision Mean?
Many people think 20/20 vision = perfect vision, but it actually means:
- You can see clearly at 20 feet what most people see at 20 feet.
Other key vision factors include:
- Peripheral vision
- Eye coordination
- Depth perception
- Focusing ability
- Color vision
Did you know?
- 20/15 vision is sharper than average.
- 20/200 vision is considered legal blindness in many countries.
Does Vision Get Worse With Age?
Your eyesight naturally changes over time. While vision itself doesn’t “worsen” just because of age, your risk for eye diseases increases after age 50. Common conditions include:
- Age-related macular degeneration (AMD)
- Cataracts
- Glaucoma
- Diabetic retinopathy
Tips to Protect Your Vision:
- Wear sunglasses outdoors.
- Use protective glasses during sports or when working with tools/chemicals.
- Maintain healthy blood pressure.
- Eat a balanced diet and exercise regularly.
How Often Should You Get Your Eyes Checked?
Your prescription can change – sometimes without you noticing. Regular eye exams are essential.
- Adults (19–40) with vision problems: Every 2 years
- Adults (40+): Once a year
- No vision issues:
- Every 5 years until 30
- Every 2–4 years between 40–65
- Every 2 years after 65
See your doctor sooner if you notice sudden changes in vision.
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Key Takeaway
Your eye prescription isn’t just numbers – it’s a roadmap to clear vision. Regular check-ups not only keep your glasses or contacts updated but also help detect serious eye conditions early.
If you’re struggling with blurred vision or need a new prescription, book an appointment with an eye specialist today.
