How do I choose lens index (1.56 / 1.61 / 1.67)?
Lens index refers to how efficiently a lens material bends light. In simple terms: the higher the index, the thinner the lens—especially for stronger prescriptions. Choosing the right index helps balance thickness, weight, appearance, and price.
Quick Answer (Most Customers)
- 1.56 → Best for low prescriptions and everyday value
- 1.61 → Best for medium prescriptions—thinner and lighter
- 1.67 → Best for higher prescriptions and the thinnest appearance
Use This Simple Chart
Choose based on your SPH (Sphere) value. If the prescription differs between your eyes, use the stronger eye as your reference.
| Your Prescription (SPH) | Recommended Index | Why |
|---|---|---|
| Up to about -2.00 or +2.00 | 1.56 | Great value with standard lens thickness |
| Around -2.25 to -4.00 or +2.25 to +4.00 | 1.61 | Noticeably thinner and lighter |
| About -4.25 or stronger, or +4.25 or stronger | 1.67 | Provides a thinner appearance for stronger prescriptions |
If you have a high CYL value for astigmatism, such as -2.00 or stronger, consider choosing one index higher because the lenses may appear thicker at certain edges.
What Changes When You Upgrade the Lens Index?
1.56 Standard Index
- Best for low prescriptions
- Most budget-friendly option
- Suitable for larger frames when your prescription is low
1.61 Thin and Light
- A popular balance of price, thickness, and weight
- Provides thinner edges and a lighter feel
- Ideal for medium prescriptions and everyday wear
1.67 Ultra-Thin
- Best for higher prescriptions
- Minimizes lens edge thickness, especially for minus prescriptions
- Can improve the appearance of lenses in larger, semi-rimless, or rimless frames
Frame Size and Shape
Larger frames generally produce thicker lenses. If you are choosing a wide or oversized frame, consider upgrading to 1.61 or 1.67 sooner.
Fast Decision Guide
- My SPH is low, around -0.25 to -2.00 → Choose 1.56
- My SPH is medium, around -2.25 to -4.00 → Choose 1.61
- My SPH is strong, around -4.25 or stronger → Choose 1.67
- My frame is large or my CYL is high → Consider choosing one index higher
Need Help Choosing?
Email us with a photo or written copy of your prescription, including your SPH, CYL, and AXIS values, together with the link to your chosen frame. Our team will recommend a suitable lens index for comfort, thickness, and appearance before production.