All sunglasses sold in Australia must offer 100% protection from Ultra-Violet light. It is often referred to as UV400.
Ultra-Violet light is the light beyond the blue end of the visible light spectrum which can cause damage to our eyes. It is the same light responsible for causing sunburn, not be be confused with the infra-red light which makes us feel hot. Infra-red can be blocked by clouds, Ultra-Violet is not.
Use of sunglasses in Australia is recommended due to our proximity to the equator and outdoor lifestyle. Our clean air and climate ensures that we see plenty of direct strong sunlight.
Polarised lenses are also UV400, but have an extra filter which reduce the amount of glare from horizontal surfaces.
if you'd like to know more about UV400 versus Polarised, check out our blog post.