Investigation for proposing eye sun protection factor (E-SPF) for sunglasses

• Grant number: 24/22508-0
• Support Opportunities: Regular Research Grants
• Start date: October 01, 2025
• End date: September 30, 2028
• Field of knowledge: Engineering - Biomedical Engineering
• Principal Investigator: Liliane Ventura Schiabel
• Grantee: Liliane Ventura Schiabel
• Host Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• City of the host institution: São Carlos
• Associated researchers: Mauro Masili

Abstract

Sunglasses standards establish requirements for eye protection against ultraviolet (UV) radiation in the range of 280 nm to 380 nm, considering only the direct transmittance of radiation through the lenses and disregarding permissible radiant exposure limits for the eyes. Sunglass frames play an important role in providing additional protection, but they are not addressed in the standards, nor is the extension of the UVA range up to 400 nm. Scattered radiation from the surrounding environment can penetrate through the gaps in the sunglass frames, reaching the eyes, which have less-constricted pupils due to the reduced brightness caused by the dark lenses. Additionally, some of this radiation enters through the frames, strikes the inner surface of the lenses, and is reflected back toward the eyes.This project aims to investigate the efficiency of UV radiation blocking up to 400 nm provided by sunglasses (both frames and lenses) by developing experimental apparatus for these measurements. The prototype will include a controlled light environment equipped with UV-A and UV-B emitting sources, a normative mannequin head (in compliance with EN168 and ISO 12311 standards) for testing, and UVA and UVB radiation detectors. Preliminary experimental setups were developed during a previous FAPESP project (2021/12240-2) for relative light-blocking measurements, validating the testing protocol. In the current setup, the aim is not only to obtain relative measurements but also to determine the radiant exposure to the cornea while wearing sunglasses.This prototype, in addition to being useful for certification bodies and/or quality control agencies for sunglasses, will enable preliminary findings on the effective ocular protection against UV-A radiation up to 400 nm provided by sunglasses as a whole, rather than focusing solely on lens transmittance, as current standards do. Based on the literature and results from previous studies regarding the spectral protection range, the field of view associated with lens categories, ICNIRP radiant exposure limits, and the findings of this study, the goal is to propose a solar protection factor for sunglasses, termed SPF-S, to serve as a solar protection label for these products.While current studies in the literature propose such a factor based solely on sunglass frames, they fail to consider the additional parameters presented in this project. These parameters include solar lens transmittance limits according to ISO 12312-1, UV radiant exposure limits for the eyes established by ICNIRP, the average visual field and UV influx for various categories of sunglasses, the upper UVA limit at 400 nm, the field of vision with solar lenses, the amount of UV radiation reaching the eye's surface, and damage weighting factors for the eye.It is important to note that the methods used in the literature to determine the protective values of frames differ from the approach proposed in this project, which involves a spherical, controlled environment. Therefore, this research project seeks to propose new requirements for sunglass standards, the equipment necessary for testing these new requirements, and the preliminary definition of a solar protection factor for sunglasses. (AU)