MICHAEL / Lens & Coating Guides
Lens Thickness & Refractive Index Recommender (1.50 to 1.74)
Match your sphere (SPH) and astigmatism cylinder (CYL) dioptres to the optimal refractive index—comparing thickness reduction, weight, prescription limits and exact package prices across 1.50, 1.56, 1.61, 1.61 Pro, 1.67 and 1.74.
How refractive index controls lens thickness and weight
A lens’s refractive index (1.50, 1.56, 1.61, 1.67 or 1.74) measures how efficiently the optical resin bends light. As the index number increases, the lens requires less physical curvature to achieve your exact Sphere (SPH) and Cylinder (CYL) power—resulting in noticeably thinner outer edges on minus (-) nearsighted lenses and flatter, lighter centers on plus (+) farsighted lenses.
Confirmed prescription boundaries & index add-on fees
| Refractive Index | Recommended Everyday SPH | Max Custom SPH / CYL | Single Vision Index Fee | Progressive Index Fee | Readers Index Fee |
|---|---|---|---|---|---|
| 1.50 Standard | Plano (0.00) & Driving up to ±2.00 D | Driving SPH -6.00 to +6.00 · CYL -4.00 (Progressive up to -8.00/+6.00) | Included in Driving (US$32) | Included in Driving (US$32) | Non-Rx Plano only |
| 1.56 Standard | 0.00 to ±2.00 D | Stock SPH -10.00 to +6.00 (CYL -2.00) · Custom SPH -12.00 to +10.00 (CYL -6.00) | +US$5 | +US$25 | +US$0 |
| 1.61 High-Index | ±2.00 to ±5.00 D | Stock SPH -10.00 to +6.00 (CYL -2.00) · Custom SPH -18.00 to +10.00 (CYL -6.00) | +US$10 | +US$30 | +US$10 |
| 1.61 Pro Extra-Hardened | ±2.00 to ±5.00 D (Active wear) | Stock SPH -10.00 to +6.00 (CYL -2.00) · Custom SPH -18.00 to +10.00 (CYL -6.00) | +US$25 | +US$45 | +US$25 |
| 1.67 Thin High-Index | ±5.00 to ±7.00 D | Stock SPH -15.00 to +6.00 (CYL -2.00) · Custom SPH -20.00 to +16.00 (CYL -6.00) | +US$50 | +US$60 | +US$50 |
| 1.74 Ultra High-Index | -6.00 to -12.00 D (up to -20.00/+16.00) | Stock SPH -15.00 to -3.00 (CYL -2.00) · Custom SPH -20.00 to +16.00 (CYL -6.00) | +US$95 | +US$109 | Not offered |
Pairing high-index lenses with the right EM frame
- Compact Lens Widths (40–45 mm) Minimize Edge Profile: Because minus lenses thicken toward the outer perimeter, choosing a compact full-rim acetate frame like MICHAEL EM23107 (40 mm), EM23218 (42 mm), EM23105 (42 mm) or EM23103 (43 mm) trims away the thickest outer zone of the lens blank.
- 360° Full-Rim Acetate Conceals the Bevel: All 17 MICHAEL EM frames feature full-rim construction, neatly enclosing the lens edge inside the acetate or TR90 eyewire.
Frequently Asked Questions
When should I upgrade from 1.61 to 1.67 or 1.74 high-index lenses?
If your SPH is stronger than ±4.00 D (or combined SPH + CYL exceeds ±4.50 D), upgrading to 1.67 Thin High-Index (+US$50 Single Vision / +US$60 Progressive index fee) or 1.74 Ultra High-Index (+US$95 Single Vision / +US$109 Progressive index fee) noticeably reduces edge thickness and lens weight.
What is the difference between 1.61 Standard and 1.61 Pro High-Index?
Both have a 1.61 refractive index, but 1.61 Pro (+US$15 over 1.61 Standard) adds extra-hardened tensile resilience and reinforced scratch-resistant hard-coating for active daily wear.
Is 1.74 available for Polarized Sunglasses or Reading glasses?
In the confirmed MICHAEL schedule, 1.74 Ultra High-Index is available for Single Vision and Progressive Clear, Blue-Light, Photochromic and Photochromic + Blue-Light packages. Colored Sun, Polarized and Reading packages top out at 1.67 Thin High-Index.