the increased susceptibility to scratch

Although the glass than plastic, it keeps its shape, in the heat. This means, glass lens will do better than plastic, if not be careful in the heat of the afternoon, in the instrument panel. Glass is a scratch-resistant than plastic. However, no shatterproof glass lens. If you hit your face, use fixture glasses can break, can foreknow the ugly results.
The use of these two types of high quality glasses of CR-39 and polycarbonate plastic. The optical quality of CR-39 is made of hard plastic resin. It is generally considered the best, is the most common plastics used in sunglasses lenses. The weight of the glass, which means it is not half so much weight in the face. Exceeds the requirements of impact resistance, because of its molecular structure.
Polycarbonate is widely used, is considered to be the second most common optical plastics. A disadvantage is the increased susceptibility to scratch and wear resistance, but with hard coating, its scratch-resistant is similar to the CR-39.
The next step, we must consider the color of the lens. Let us try to simplify this topic, shows some arbitrary polarized lenses, there are four basic colors, you through (I'm not here to talk about the lens mirror outside): dark brown, light brown, green, and grey. Some companies vermilion, copper, amber, and other colors. They just four basic changes in our.
Fishermen have never want a green lens. They do not provide enough contrast, to detect fish in any case. Coffee is best for coastal fisheries in the bright sunlight. Light brown (Amber) lens is the most suitable for offshore in dim light or cloudy conditions of fisheries.