Many people believe that sun protection is only necessary for exposed skin, unaware of the even greater harm that ultraviolet (UV) rays can cause to the eyes. UV rays penetrate the outer eye into the inner structures, affecting the conjunctiva, cornea, lens, vitreous, and retina. This can lead to conditions such as conjunctivitis, keratitis, pterygium, pinguecula, cataracts, retinal degeneration, and other serious eye diseases.

This is where photochromic sunglasses come into play. These advanced lenses automatically adjust to light conditions, darkening in response to UV exposure and becoming clear indoors. By providing UV protection and adapting to changing environments, photochromic sunglasses offer not just convenience but also enhanced protection.

As the saying goes, "Where there is strength, there is a counterforce." The stronger the UV rays, the stronger the protection your sunglasses should provide. Eye sun protection, especially with the right technology, can effectively counter UV damage.

Sunglass UV Protection Index

The UV protection of sunglasses, including photochromic sunglasses, depends on their UVB and UVA protection ratings. UV protection is usually classified into two levels:

• Level 1 offers 90% UVA and 99% UVB protection.
• Level 2 offers 70% UVA and 95% UVB protection.

The standard is based on the visible light transmittance (transmittance = transmission ratio). For sunglasses with 30% transmittance, UVB transmission is ≤1.5% (30% × 5%), and UVA transmission is ≤15% (30% × 50%). Simply put, UVB <1% and UVA ≤5% are ideal. Photochromic lenses can meet these requirements while automatically adapting to light changes, providing optimal comfort and protection in various conditions.

E-SPF Sun Protection Index

E-SPF (Eye-Sun Protection Factor) is an indicator of the UV protection performance of lenses and the degree of protection they provide to the eyes. It rates any type of lens, including photochromic sunglasses and regular sunglasses. Generally, the higher the E-SPF value, the better the UV protection.

The E-SPF value of regular eyeglass lenses ranges from 3 to a maximum of 25, with E-SPF 25 being the highest value for high-transparency, colorless lenses. Sunglasses can achieve an E-SPF value of 50+. In some cases, photochromic lenses can offer superior protection, as they transition from clear to dark based on UV exposure. For instance, on bright days, photochromic sunglasses can automatically adjust, reducing the need for multiple pairs of eyewear.

UV400 Index

The UV400 index refers to the UV protection factor, meaning the lenses block  of UV rays. Specifically, it indicates that the average transmittance of UV rays below 400nm should not exceed 2%. The damage caused by UV rays depends on their wavelength, exposure time, intensity, and the strength of the eye’s natural defenses.

Lenses marked with UV400 can block  of harmful UV rays, making them the best option for UV protection. In simple terms, UV400 lenses control light transmission below 400nm, keeping it within 5%, reducing UV exposure, and protecting against cataracts, macular conjunctivitis, and retinitis. Photochromic sunglasses, especially those with UV400 protection, are an excellent choice for people engaged in outdoor activities like fishing or skiing, as they provide comprehensive UV protection while adjusting to varying light conditions.

Maat’s newly released 1.56 UV400 photochromic lenses offer UV protection and are TUV certified, making them an ideal choice

By choosing photochromic sunglasses, you are not only protecting your eyes from harmful UV rays but also ensuring comfort in both bright sunlight and low-light environments. This makes them a versatile and practical option for everyday wear.