1. If it is between 0 degrees and negative 300 degrees, it is recommended to use a refractive index of 1.56 or 1.61. Because the higher the refractive index, the thinner the lens, the better the hardness and wear resistance. If it is above 300 degrees, it is recommended to wear lenses with a refractive index of 1.67.
2. The higher the refractive index, the thinner the lens. 1.56 is ordinary ultrathin, and 1.61 is ultrathin. If it is the same brand, it can be distinguished, but the thin thickness must be similar. You need to take a Vernier scale to measure its thickness at the same distance. If you only look at the thickness of the edges, it will definitely not make you feel much.
3.1.56 lenses belong to medium refractive index lenses, which have both spherical and aspheric designs. 1.61 lenses are high refractive index lenses, with only aspheric designs. Aspherical lens can reduce the edge difference of the lens, making the vision clearer and more natural. For myopic individuals with high refractive index, it is more suitable to choose non spherical lenses with high refractive index.
