Ultraviolet (UV) Radiation: Types, UV Index, and Eye Protection
Sunlight contains different types of electromagnetic radiation, including ultraviolet (UV) rays, which are invisible to the human eye. UV radiation is classified into three types based on wavelength: UVC, UVB, and UVA. Each type affects the skin and eyes differently.
UVC
UVC (100–280 nm) is the most energetic and potentially harmful type of UV radiation. Fortunately, it is almost completely absorbed by the Earth’s ozone layer and normally does not reach the surface.
UVB
UVB (280–315 nm) is partially filtered by the ozone layer. It is the primary cause of sunburn and can increase the risk of skin cancer, cataracts, and other eye conditions after prolonged exposure. UVB also plays a role in vitamin D production.
UVA
UVA (315–400 nm) accounts for approximately 95% of the UV radiation reaching the Earth’s surface. It penetrates deeper into the skin and is associated with premature skin aging, cataracts, and cumulative eye damage. Unlike UVB, UVA can also pass through ordinary window glass.
What Is the UV Index?
The UV Index (UVI) measures the intensity of ultraviolet radiation on a scale from 0 to 11+. Higher values indicate a greater risk of damage to the skin and eyes.
• 0–2: Low risk
• 3–5: Moderate risk – wear sunglasses and sunscreen.
• 6–7: High risk – limit midday sun exposure and use protective clothing.
• 8–10: Very high risk – seek shade and use UV400 sunglasses, sunscreen, and a wide-brimmed hat.
• 11+: Extreme risk – avoid prolonged outdoor exposure whenever possible.
Protecting Your Eyes from UV Rays
Long-term exposure to ultraviolet radiation may increase the risk of cataracts, pterygium, photokeratitis, and other eye diseases. Wearing UV400 sunglasses that block 100% of UVA and UVB rays, along with a hat and limiting sun exposure during peak hours (10 a.m. to 4 p.m.), are among the most effective ways to protect your vision.