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James Stringham, Peter Smith, Leon McLin; Visual performance and glare: Spatial properties of visual obscuration. Journal of Vision 2008;8(6):949. doi: https://doi.org/10.1167/8.6.949.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The aim of this study was to investigate the relationship between the size of a glare image on the retina and the ability to detect a visual stimulus in and around the glare field. For this, we measured the ability to detect a Gabor patch stimulus through glare from 532 nm laser illumination. Methods: A three-channel standard Maxwellian-view optical system was employed. One channel projected the extended-source laser images; a second channel projected the standard laser image; and the third channel projected the background and Gabor patch, which were presented on a LCD monitor. The laser glare stimulus size ranged from a standard point source to an 8° extended-source field, and the angle between the laser glare and Gabor patch stimuli was from central, or 0° aspect, to 5° off-aspect angle. The mean luminance of the monitor was 100 cd·m−2, and the contrast of the Gabor patch stimuli was 60%. Results: The extended-source images proved to be much more effective at obscuring the Gabor targets than the standard, point-source laser. In cases where the extended-source laser covered the Gabor patch, at least 1.5 log units less retinal irradiance was necessary to obscure the target, compared to the point-source laser. Additionally, as the extended-source laser stimulus size increased, progressively less retinal irradiance was needed to obscure targets “under” the laser. This suggests a spatial summation effect for obscuration by glare.
Conclusions: Glare effectiveness increases with the size of the glare image, and, for large sources, spatial summation effects contribute to this increased effectiveness.
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