Sunglasses come with labels that tell you if they offer optimal UV protection. Look out for one of these three labels:
The “100% UV protection” label is self-explanatory. It shows that the sunglasses will block 100 percent of the sun’s harmful rays.
- Block both UVA and UVB rays
The “blocks UVA/ UVB radiation” label is more specific. It shows that the sunglasses block both UVA and UVB radiation.
UVA radiation makes up 95% of the UV rays that reach us. They can damage the retina and cause blurry vision. On the other hand, UVA radiation makes up 5% of the UV rays that reach us. However, they can damage the cornea and lens to cause eye sunburn and cataract development.
There are three types of UV radiation - UVC, UVB, and UVA. UVC is filtered by the atmosphere and does not reach the earth's surface. Only UVA and UVB reach us from the sun. So, if a pair of sunglasses blocks UVA and UVB radiation, they offer 100 percent UV protection.
The “400NM or UV400” label is even more specific. It specifies the wavelengths of UV light that the sunglasses block from entering your eyes. The “400NM or 400UV” label shows that the sunglasses block all UV light with wavelengths up to 400 nanometers from entering the eyes.
UV radiation covers the wavelength range of 100 - 400 nanometers. So, if a pair of sunglasses block UV wavelength up to 400nm, it offers 100 percent UV protection.