Most people check the SPF number of sunscreen to protect themselves from sunburn, but few of us know for sure if our sunglasses are shielding our eyes from harmful UV radiation. Scientists in Brazil have developed a self-service kiosk where 800 people have tested whether their shades are really protecting their eyes, and the service could become more widespread.
The way the kiosk works, and proof that it is as effective as lab tests are described in a paper in the open access journal BioMedical Engineering OnLine.
UV radiation from the sun can cause serious eye problems. Lifelong exposure to sunlight is associated with melanoma of the eye and other cancers, while the WHO estimates suggest that up to 20% of cataracts may be caused by overexposure to UV radiation. UV exposure has also been directly linked to other disorders like photokeratitis and photoconjunctivitis - sunburn of the cornea and conjunctiva, and pterygium, where the conjunctiva grows over the surface of the eye.
Some sunglasses give inadequate protection from UV radiation. Even those with UV protection certification can become less effective over time, and there is no worldwide standardization for these certifications, so it's useful to check how much protection they are really giving.
The first prototype kiosk was installed on the University of Sao Paulo campus in Sao Carlos for the public to use free of charge, with the intention of rolling them out in large public places such as malls and beaches. To find out how well their sunglasses work, users place their sunglasses in the kiosk, and the machine performs a transmittance test to find out how much UV radiation the lenses allow to pass through. Of 800 users of the prototype, 20% found their sunglasses were not giving them adequate protection.
Lead author Liliane Ventura from University of Sao Paulo said: "The easiest and most comprehensive way to protect a population against harm to human health is to provide the public a simple and accessible means of learning how to protect themselves. Publishing our research in an open access journal plays an important role in ensuring that this happens."