Lens materials
High index
Optical glossaryLens materials
In the CLIFF range, materials of 1.67 and above, used to keep strong prescriptions thin. Buys thinness, not clarity.
Estimated edge-thickness reduction
- 1.50
Standard referenceStandard 1.50 material
- 1.56
Up to 10% thinnerthan 1.50 at −6.00, indicative
- 1.60
Up to 20% thinnerthan 1.50 at −6.00, indicative
- 1.67
Up to 30% thinnerthan 1.50 at −6.00, indicative
- 1.74
Up to 40% thinnerthan 1.50 at −6.00, indicative
- Index 1.50: Standard reference
- Index 1.56: Up to 10% thinner
- Index 1.60: Up to 20% thinner
- Index 1.67: Up to 30% thinner
- Index 1.74: Up to 40% thinner
Relative comparison · indicative percentages against 1.50, not measurements
In more depth
High-index materials exist for strong prescriptions, where a standard lens becomes visibly thick at the edge or bulbous at the center. Each step up removes curvature, and with it thickness and weight, while leaving the correction exactly the same.
Their optical price is dispersion and reflection. A lower Abbe number can show faint color fringes when looking well off-center through a strong lens, and a bare high-index surface reflects noticeably more, which makes a good anti-reflective coating part of the lens rather than an extra.
Across the CLIFF index range
| Index | Material | Curve depth | Reflection | Abbe |
|---|---|---|---|---|
| 1.67 | MR-7 / MR-10 | 75% | 6.3% | 31–32 |
| 1.74 | MR-174 | 68% | 7.3% | 32–33 |
Curve depth is relative to a 1.50 lens of the same power, and reflection is for one bare, uncoated surface — both calculated from the index itself. Material and Abbe number are the material manufacturers' published figures, not CLIFF measurements.