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 + lighter)
- 1.67 → Best for higher prescriptions (thinnest look)
Use This Simple Chart
Choose based on your SPH (Sphere) value (use the stronger eye if they’re different):
| Your prescription (SPH) | Recommended index | Why |
|---|---|---|
| Up to about -2.00 (or +2.00) | 1.56 | Great value, normal thickness |
| Around -2.25 to -4.00 (or +2.25 to +4.00) | 1.61 | Noticeably thinner & lighter |
| About -4.25 and above (or +4.25 and above) | 1.67 | Thinnest look for stronger prescriptions |
If you have strong CYL (astigmatism) (e.g., -2.00 or more), consider going one step higher because lenses can look thicker at the edges.
What Changes When You Upgrade Index?
1.56 (Standard)
- Best for light prescriptions
- Most budget-friendly
- Ideal for larger frames if your prescription is low
1.61 (Thin & Light)
- Best “sweet spot” for most people
- Thinner edges, lighter feel
- Great for medium prescriptions and everyday wear
1.67 (Ultra Thin)
- Best for higher prescriptions
- Minimises lens edge thickness (especially in minus prescriptions)
- Improves appearance in larger frames or rimless styles
Frame size & shape
Bigger frames generally create thicker lenses. If you’re choosing a wide or oversized frame, consider 1.61 or 1.67 sooner.
Fast Decision Guide
- My SPH is low (around -0.25 to -2.00) → 1.56
- My SPH is medium (around -2.25 to -4.00) → 1.61
- My SPH is strong (around -4.25 and above) → 1.67
- My frame is large OR my CYL is high → go one index higher
Need Help Choosing?
Email us with a photo or text of your prescription (SPH/CYL/AXIS) and your chosen frame link. We’ll recommend the best index for comfort and appearance before production.