Disability glare happens when a light source causes a diffusive intraocular light scattering, which reduces target visibility and results in functional impairment. It is important to understand how disability glare harms visual function science it adversely affects the daily activities of a substantial fraction of the population. However, previous studies were of limited values in three aspects. Firstly, the effects of disability glare on visual performance have been mainly measured with visual acuity, which does not predict the actual visual performance on individual basis in daily life. The effects of glare on a lot of visual tasks that are frequently performed in real world have been ignored. Secondly, previous studies generally suggested that the reduced contrast caused by glare is the underlying mechanism of the impaired visual performances. But some recent studies suggested that the reduced contrast couldnít account for all the visual functional changes. Thirdly, most previous studies were done with steady glare. But, glare sources are often transient in nature with sudden onset. What happens during in the first several seconds is critical. Here we propose to investigate the effect of sudden onset glare on motion detection and shape discrimination, the representative functions of temporal and spatial vision, along with contrast sensitivity. The amount of glare entering the eye will be controlled with light source, entry angle and artificial pupil size. The threshold of each visual function will be measured without glare first as controls. Then we will map out the dynamic changes in the threshold values of different visual functions after the sudden onset of a glare with the stimulus onset asynchrony method. Comparing the changes across different visual functions will shed new lights on the understanding of glare's effect on vision.