Changes in contrast sensitivity perception due to protector screens for welding tasks : conventional protective optical filter vs novel protective optical filter of selective absorbance

Abstract

Purpose: To evaluate diff erences in contrast sensitivity perception in central visual field using protective optic fi lters for welding tasks. Two interposed filters are compared: a conventional protective optical fi lter and a new protective optical fi lter with selective absorption designed by University Complutense of Madrid (UCM). Methods: 36 people of working-age were included in a cross-sectional prospective observational study. Contrast sensitivity threshold in central visual fi eld was evaluated using FDT Perimeter, C-20 procedure (Humphrey systems, USA). ! ree conditions were set: a) without optical fi lters; b) with an interposition of conventional protective optical fi lter for welding (shade 2.5) and c) with an interposition of a novel protective optical fi lter of selective absorbance that fully blocks the short wavelength light and minimally attenuates the remaining bands of the visible spectrum. Results: Contrast sensitivity in all visual fi eld areas evaluated diminished 91-98% with the conventional protective optical fi lters. UCM optical fi lters provoked a low-level decrease in contrast sensitivity (9-19%). Mean contrast sensitivity thresholds were 29.5±5dB, 25.5±4dB, 1.8±2dB in conditions a, b and c respectively Conclusion: Conventional optical fi lters resulted in drastically diminished contrast sensitivity. UCM optical fi lter minimally diminish the visual function, allowing a suitable visibility and also maintaining an appropriate level of protection against phototoxic damage.