Visualizing visual impairments

We developed and evaluated methods to visualize the limitations of visually impaired persons. Three types of simulation were developed: (i) fixation independent, showing which elements remain visible after ample inspection, related to object recognition, (ii) fixation dependent, showing which elements remain visible in the entire visual field while fixating one part of the image, related to search, and (iii) the effect of glare, an important factor of low vision in for instance cataract patients. In experiments with impaired and unimpaired subjects we determined the extent to which a natural image can be blurred before it can be discriminated from the original, and how this is linked to Landolt-C visual acuity. The relationship between blur threshold and minimum angle of resolution was found to be independent of the cause of reduced vision: visual impairment, reduced contrast, or eccentric viewing. Based on this finding we propose a fixation independent simulation in which the local blur varies with local contrast, linked by the subject's contrast sensitivity function. The fixation dependent simulation type is derived from the peripheral acuity using the relationship between blur threshold and acuity, and perimeter data describing visual field defects. The glare simulation is based on a validated CIE model describing the veiling luminance due to a light source, treating all pixels as independent light sources. These visualizations should give unimpaired persons insight into the problems faced by persons with low vision. The fact that the visualizations are validated by human observer experiments make them suitable for evaluating and adapting designs of architecture, public (road) infrastructure, and products to the needs of the low vision community. Adapted from the source document.