UV radiation is an invisible component of the light spectrum that poses a significant risk to eye health. It is categorized into UVA, UVB, and UVC. While UVC rays are mostly filtered by the atmosphere, UVA and UVB rays reach the surface. This makes protective eyewear, like safety glasses, a necessary safeguard in many settings.
The Inherent UV Protection of Standard Safety Glasses
The majority of modern safety glasses are constructed using polycarbonate, chosen primarily for its superior impact resistance. This thermoplastic material is lighter than traditional glass and more durable than standard plastics like CR-39. The chemical structure of polycarbonate naturally absorbs nearly 100% of the UV spectrum, including UVA and UVB rays, without requiring specialized coatings or tints.
This inherent property means polycarbonate safety glasses offer broad-spectrum UV protection by default. Lenses made from CR-39 plastic or glass, however, require additional treatment to achieve comparable UV filtration. Tinting manages visible light but is separate from the material’s UV-blocking capability; a clear polycarbonate lens provides the same UV protection as a dark-tinted one.
Identifying Certified UV Protection
Verifying safety eyewear protection requires looking for specific compliance markings. In the United States, the American National Standards Institute (ANSI) Z87.1 standard dictates requirements for occupational eye protection. Safety glasses meeting this specification must be permanently marked on the frame or lens.
The standard requires that UV-designated eyewear block at least 99.9% of harmful radiation. This protection level is indicated by a “U” marking followed by a scale number, such as “U6,” which signifies the highest level of UV filtration under the Z87.1 system. Users should look for the primary “Z87” or “Z87+” mark, which certifies impact resistance, and then check for the specific “U” designation to confirm UV blocking performance.
Immediate and Long-Term Effects of Ocular UV Exposure
Failing to protect the eyes from UV radiation carries both immediate and cumulative health consequences. Short-term, intense exposure can cause photokeratitis, often described as a “sunburn of the eye.” This temporary, painful condition affects the cornea, leading to symptoms like redness, a gritty feeling, and extreme light sensitivity.
Cumulative, long-term exposure significantly increases the risk of developing several serious eye diseases. Chronic UV damage contributes to the development of cataracts, which is a clouding of the eye’s natural lens. It is also linked to pterygium and pinguecula, which are growths on the surface of the eye. Prolonged exposure is also associated with an increased risk of age-related macular degeneration, which affects the central retina and can severely impair central vision.