The influence of glare generated by an LED lamp on pupillary behaviour: considerations about colour temperature

Abstract

The increasing adoption of LED technology in public road networks has triggered important questions regarding its impact on visual performance. Furthermore, there is a lack of information concerning the effect of glaring lamps with different Correlated colour temperatures (CCTs) on pupillary diameter dynamics This study aims to elucidate the role of CCT from commercial LED glaring lamps in the pupil light reflex.Measurements were conducted using a two-channel Maxwellian view optical system, which projected a 10º adaptation beam from a 4000K LED illuminant at three luminance levels: 0.1, 1, and 10 cd/m2. A glare of 52 lux was generated for 3 s at 10º temporal retina of the observer, using randomly selected two LED lighting sources of 2700 K and 6500 K. A CCD camera-based infrared pupilometer, integrated into the optical bench, was employed to measure pupillary diameter and eye position. Nineteen young participants, aged between 18 and 30 years, free of ocular pathologies, with refractive errors ranging between ± 6.00 D, and without alterations in colour vision, were recruited for this study.A significant effect of luminance on pupillary diameter variation was observed for both lamps with different CCTs. The maximum diameter achieved before glare onset and the minimum diameter reached during glare presentation decreased with higher background luminance levels. However, no effect of the LED lamp CCT on pupillary diameter behaviour was observed, regardless of luminance.The absence of an effect of the LED lamp CCT on pupillary diameter can be attributed to the similarity in the spectral distributions of both lamps. Consequently, CCT may not be the most suitable metric for predicting pupillary behaviour in response to glare induced by LED technology.