Tests on sunglasses show shortcomings in protection against ultraviolet rays

Ultraviolet radiation on solar energy is one of the causes of a series of eye diseases, including cataracts and a type of cornea inflammation (photo cooker atitis), which can be delayed or prevented by using UV protection, with sunglasses the most popular accessory for this function are. A study, however published in the diary Research into biomedical engineering Increases alarm bells by revealing shortcomings in this protection.

The study analyzed the effectiveness of 12 models of sunglasses and it turned out that only one model met the safety limits for exposure to ultraviolet radiation established by the International Commission on Non-ionizing Radiation Protection (ICNIRP).

Researchers from the Ophthalmic Instrumentation Laboratory at the São Carlos School of Engineering of the University of São Paulo (EESC-SPESP) in Brazil showed that the lenses do not meet at least one of the safety limits in the standards and that they lose in time That they lose part of their ability to block UV radiation, which increases the risk of eye damage.

Only one lens turned out to be “optimal” because it completely blocked the radiation, even after the aging test, which simulated 2500 hours of sun exposure to the sun. The study does not mention glasses brands.

To guarantee effective and extensive vision protection, scientists suggest that the industry takes on ICNIRP limits as standard practice, which improves product quality.

The standards for certification of sunglasses and eye protection set limits for solar strangling filters at wavelengths between 280 and 380 Nanometers (NM). The World Health Organization (WHO) and the International Commission set these limits between 280 and 400 Nm. UV radiation is divided into three tires – UVC (100 to 280 Nm), UVB (280 to 315 Nm) and UVA (315 to 400 Nm).

“We have investigated this in our lab since the 1990s. We have developed a science that can be used as a basis for determining safety standards and standards. Nowadays we are internationally recognized and cited by various authors in books and guidelines,” says Professor Liliane Ventura of the EESC-SPSP Department of Electrical and Computer Engineering, corresponding author of the article.

Ventura also leads patent applications for two prototypes: one to measure the radiation exposure of the eye on direct, diffuse and reflection from the inside of sunglasses, and another for testing the blocking of ultraviolet radiation in sunglasses that are sold to the public . Both are processed by the USP Innovation Agency for submission to the National Institute of Industrial Property (INTI).

Ventura and her student at the time, Artur Duarte Loureiro, recently granted a patent for a technology that rates the state of sunglasses for driving through the transfer of light on different wavelengths, such as green, yellow and red.

Researcher Mauro Masili, first author of the article and a member of the laboratory, highlights another study of the group, published in March 2024 in the magazine Scientific reportsWhich shows that, regardless of the category lenses – can or darker – glasses of UVA protection of more than 86%must guarantee. Lenses are categorized from 0 (lightest) to 4. A 0 is recommended for situations in which there is little or no clear sunlight. A 4, which is very dark, is not recommended for driving.

The results showed that the protection of less than 86% can even increase the risk of eyes health, because the lenses make more UV radiation possible. Contrary to what has been argued in the scientific literature, this increase is not due to the dilation of the student caused by sunglasses, but rather on widening the field of vision.

“We have compiled a table that calculates UV, UVA and UVB protection. In terms of pupil dilation there are no bad glasses. They will all protect. But if we absorb the gap of the eyesight, that changes into clear ones Extra -environments, the natural reflex is to try to close your eyes and to ripple your foreheads to reduce the lenses. Masili out.

That is why extending protection to 400 Nm can minimize the risk of unnecessary exposure, according to the study.

Comings and ins and outs

Since the end of the nineties, when there were no standards for the requirements of sunglasses protection in Brazil, Ventura and Masili have helped the regulatory authorities to determine these guidelines, including the first analyzes of optical characteristics that the professor performed for the National Institute of Metrology, Quality and Technology (Inmetro) in 1997, based on international standards.

In 2003, the Brazilian Association of Technical Standards (ABNT) NBR 15111, which established the physical characteristics of sunglasses for general use, such as driving and transit, published with parameters similar to those in Europe. It found that the protection in Brazil filters between 280 and 380 Nm.

De Standaard was revised in 2013, After research Performed by the group, which increases the UV protection to 280-400 Nm and the radiation resistance test is increased from 25 hours to 50 hours. In 2015, however, it was withdrawn and replaced by ISO 12312-1, which restored the parameters of UV protection filters from 280 to 380 Nm.

In 2016, another study carried out by the two researchers Exposure to solar radiation in 27 Brazilian state capitals and 110 capitals in the northern hemisphere and showed that the test was not effective to ensure the protection of sunglasses against UV radiation exposure.

Currently there is no requirement that sunglasses are certified for sale in Brazil. For equipment used to control vehicles, for example, it is possible to perform the analysis using a spectrophotometer, equipment used for scientific purposes and treated by specialists.

Ventura says she is developing a prototype for measuring radiation exposure of the eye, with a proposal for a label of the sun protection factor that can help consumers choose to shop.