Effect of glare on contrast sensitivity at various external noise levels

Abstract

BackgroundGlare can reduce a driver's visual performance, increasing the risk of traffic accidents. The ability of the visual system to process spatial information can be assessed with the contrast sensitivity function (CSF); the CSF is decreased by glare. ObjectiveThe current study had three key aims: to examine whether and how glare-induced contrast sensitivity (CS) loss is modulated by spatial frequency (between 0.5 and 16 cycles per degree) and external noise (zero, low, or high); to evaluate subjective feelings of discomfort under different glare conditions; and to investigate the underlying mechanisms with a perceptual template model (PTM). MethodsParticipants completed a contrast detection task with quick CSF algorithm and reported their subjective feelings under nonglare, steady-glare, and transient-glare conditions. ResultsSteady and transient glare both reduced CS to comparable degrees. When external noise was absent, the CS reduction was largely dependent on spatial frequency, with a larger amount of CS loss at lower spatial frequencies. When external noise was present, the CS reduction was independent of spatial frequency. In addition, the reduction in the area under the log CS function (AULCSF) under steady-glare condition was roughly the same as that under transient-glare condition, regardless of external noise. However, participants reported greater discomfort under transient-glare condition than under steady-glare condition. Moreover, the AULCSF was reduced more under the zero-noise condition than under noise conditions. The PTM suggested that an increase in internal noise and an impaired perceptual template explained the glare-induced CS loss. ConclusionThe glare-induced CS loss was modulated by spatial frequency and external noise. Steady glare and transient glare affect CS to a similar extent, but steady glare produces less discomfort. Glare attenuates signals and weakens noise exclusion ability. ApplicationThis study advances our knowledge on glare-induced CS loss and its underlying mechanisms. The qCSF procedure with external noise should be utilized in future studies to investigate the effect of various light sources on visual function.