Just one more thing...
In general, sport lenses have a strong curvature or bend in order to protect the eyes against environmental influences. The curvature of the middle area of the lens varies according to the width of the wearer’s head. The lenses for sport glasses are extremely lightweight, robust and they guarantee the best optical quality, despite their strong curvature. The frames of designer glasses are also often very curved.
You can choose a variety of indexes, materials and coatings for these lenses. Different treatments can be added as well: color, photochromic, polarized.