I. What is the refractive index of a lens?
1.56, 1.60, 1.67, 1.74: these numbers represent the lens's refractive index, which indicates its ability to bend light according to the material. Under identical conditions of frame size and grade, the higher the refractive index, the thinner the lens flange will be and the lighter the lens overall.
The refractive index depends on the lens's base material and is a key parameter when choosing eyeglasses, directly affecting aesthetics, weight, and visual comfort.
II. Suitable individuals according to the main refractive indices
1.56 Standard Refractive Index
A basic model with excellent value for money, high Abbe index, delivering sharp images, transparency, and durability—ideal for individuals with mild myopia up to 300 degrees and students. Its drawback is that the edges are thicker when using higher prescriptions.
1.60 Balanced Refractive Index
Excellent overall performance, balanced between thinness, clarity, and price, suitable for moderate myopia from 0 to 600 degrees, compatible with most frames, and the leading model sold in stores.
1.67 High Refractive Index
Significantly slim effect, greatly reducing lens thickness—ideal for medium myopia ranging from 600 to 900 degrees, combining beauty and lightweight design.
1.74 Ultra-thin Refractive Index
The highest index available in resin lenses on the market, extremely thin and specifically designed for individuals with severe myopia (over 800 degrees), effectively addressing the issues of weight and protruding edges found in thick lenses.
III. Key tips when choosing: not all higher refractive indices are better
The higher the refractive index, the lower the Abbe number, which slightly increases chromatic dispersion and reduces color fidelity, while also raising the price.
One should not blindly opt for 1.74 if you have mild myopia, as it not only increases the budget but also reduces visual comfort with medium or low-index lenses. When using large frames, it is recommended to moderately increase the refractive index to reduce the sensation of heaviness.
IV. How to Choose Accurately
Carefully evaluate by combining your degree of myopia, frame size, and budget: for mild myopia, choose 1.56 or 1.60; for moderate myopia, prioritize 1.60; for high myopia, consider 1.67 or 1.74. A professional optometrist will provide you with the optimal combination based on your pupillary distance and frame width.
