A layer coated on the external surface of the lenses, with special chemical composition, absorbs part of the sunlight and reflects the remaining. It appears as the coating color you see: a shiny effect and a stylish look. Some coating layers can also absorb light passing the lenses, slightly altering the vision color. 

Photochromic lenses turn darker under sunlight, specifically the UV light in sunlight, and turn lighter under shadow. The color changing is due to the silver halide crystals in the lenses. Under sunlight, the silver crystals become unbound state, which form small silver aggregations inside the lenses. These small aggregations cannot transmit light, and instead absorb light, which cause the lenses have lower light transmission rate, in another word, darker. Under shadow the above mentioned chemical process is reversed, which cause the lenses lighter.

Polarized photochromic lenses have the advantages of both polarized lenses and photochromic lenses: reduce flare, improve contrast and clarity, darker under sunlight and lighter under shadow.

Natural light contains light wave oscillating at all directions. In particular, light reflected from surface such as flat road, windshield or water surface mostly oscillates horizontally. When being tailored at a particular direction, polarized lenses only allow the light vertically oscillating passes, therefore, can effectively remove glare from reflective surface.  

This make polarized lenses perfect for fishing, driving, riding, hiking and other outdoor activities as well as daily wearing.

As the consequence of removing glare, polarized lenses can significantly improve the contrast and clarity, thus bring significantly comfortable vision.

Most sunglasses lenses adapt a curved shape, which may bring distortion. With tamper correction technology, the lenses are manufactured with different thickness from center to edge, this special procedure compensates the distortion generated by curving, and finally the lenses create a natural undistorted vision.

Many light sources can generate harmful rays, especially sunlight, which contains ultraviolet (UV) rays, such as UVA, UVB and UVC. These UV rays can damage human body. Human eyes can absorb UVB light, which cause severe damage on vision; and tanning ray is the light which can burn human skin. Lenses with UV protection capability can remove UV rays effectively, thus it can protect human from being hurt.

All Walleva lenses are coated with a combined oleophobic and hydrophobic layer. It is a clear thin layer, which protects the lenses from moisture, dirt, grease, and oily smears. This layer is also hardened for anti-scratch capability (under normal usage).