Sunglasses typically filter 99-100% of UVA and UVB light (wavelengths up to 400nm).
Here's a breakdown:
- UV Protection: The primary function of sunglasses is to protect your eyes from harmful ultraviolet (UV) radiation. Fortunately, most sunglasses available today, regardless of price, offer excellent protection in this regard.
- UVA and UVB Rays: These are the two types of UV rays that sunglasses are designed to block. Exposure to these rays can lead to various eye problems, including cataracts and macular degeneration.
- Filtration Range: Sunglasses commonly filter 99% to 100% of UVA and UVB light with wavelengths up to 400 nanometers (nm). This is the critical measurement for UV protection.
- Visible Light Reduction: Beyond UV protection, sunglasses also reduce the intensity of visible light, which helps to alleviate glare and improve visual comfort in bright conditions. The amount of visible light filtered is often expressed as a percentage and varies depending on the lens tint and darkness.
- Polarization: Polarized lenses reduce glare from reflective surfaces like water or snow. Polarization is a separate feature from UV protection and doesn't inherently guarantee UV blockage; however, many polarized sunglasses also offer full UV protection.
In summary, while the amount of visible light filtered can vary, almost all sunglasses readily available offer near complete protection from harmful UVA and UVB rays up to 400nm.
