High-Index Caliper Thickness Optimization in Blue Cut Spectacles: Weight Reduction & Base Curve Flattening

For an identical refractive power $F$, the radius of curvature $r$ expands proportionally to $(n - 1)$:

$$r_2 = r_1 \cdot \left(\frac{n_2 - 1}{n_1 - 1}\right) \implies s_2 \approx s_1 \cdot \left(\frac{n_1 - 1}{n_2 - 1}\right)$$

Theoretical sagitta and thickness reduction compared to standard CR-39 ($n=1.50$):

• 1.60 MR-8: $\frac{0.50}{0.60} = \mathbf{0.833} \implies \mathbf{16.7\% \text{ Thinner}}$ (Sweet spot: high Abbe $42$, ultra-tough).
• 1.67 MR-7: $\frac{0.50}{0.66} = \mathbf{0.758} \implies \mathbf{24.2\% \text{ Thinner}}$.
• 1.74 MR-174: $\frac{0.50}{0.74} = \mathbf{0.676} \implies \mathbf{32.4\% \text{ Thinner}}$.

According to the Beer-Lambert Law ($T = e^{-\alpha C t}$), in-mass blue light filtering depends on physical optical path length (thickness $t$). In high minus lenses, while the edge is thick ($4\text{--}6\ \text{mm}$), the optical center thins down to $1.0\ \text{to } 1.5\ \text{mm}$. Using electronic digital dial calipers ($\pm 0.01\ \text{mm}$ resolution), ELLASUV technicians enforce strict center-thickness baselines:

$$t_{\text{center}} \ge 1.10\ \text{mm (MR-8)} \implies \mathbf{\text{Guarantees } >85\% \text{ Blue Filtration Across Entire Center}}$$

When mounting a $-7.00\ \text{D}$ lens in a metal wireframe, placing the bevel at the front surface (1/3 – 2/3 rule) forces all remaining edge thickness backwards toward the cheek, hiding edge rims from casual observers and maximizing cosmetic elegance.