Thickness and Weight of Ophthalmic Lenses: Software Optimization for Thinner, Lighter Lenses

One of the key parameters is the refractive index. A material with a higher refractive index bends light more efficiently and therefore allows a thinner lens to provide the same optical power. However, thinner does not necessarily mean lighter: as the refractive index increases, the material density generally increases as well.

Calculations performed on lenses from +8 dpt. to -8 dpt. highlight this relationship. For negative lenses, moving from refractive index 1.5 to 1.6 produces a significant weight reduction. Between 1.6 and 1.67 the advantage becomes smaller, while 1.74 high-index lenses are not necessarily lighter than 1.67 lenses. Below -6 dpt., they can even be slightly heavier. Nevertheless, the 1.74 material consistently provides a lower edge thickness.

Material choice, however, is only part of the solution. Modern lens calculation software can optimize diameter, surface geometry, thickness and consequently lens volume and weight. One technique is elliptical calculation, or pre-calibration, which determines the minimum lens size according to frame shape and centering parameters. Reducing the required semi-finished lens dimensions can decrease thickness, weight and production costs.

The study also examines advanced thickness optimization through the Crea Size 2.0 algorithm, an evolution of conventional lenticularization. Instead of applying an abrupt peripheral curvature change, the technology follows the frame shape, reducing lens thickness while limiting the impact on peripheral vision.

The comparison shown in Figure 6 is particularly significant. In the analyzed lens, standard calculation produces a 6.24 mm center thickness, elliptical calculation reduces it to 5.20 mm, while Crea Size 2.0 reaches 4.65 mm. Since the material remains unchanged, reducing volume also results in a lighter lens.

The research therefore demonstrates that increasing the refractive index always reduces lens thickness, but does not automatically reduce weight. Combining appropriate materials with software optimization algorithms offers a more effective approach to producing thinner, lighter and potentially more comfortable spectacles.