Visual search-based design and evaluation of screen magnifiers for older and visually impaired users

The purpose of this study was to achieve the following goals: apply some principles in visual search theory to design and develop a screen magnifier; evaluate if applying such features could increase user performance; and make some recommendations for designing a screen magnifier according to the findings of the study. In order to achieve these goals, a screen magnifier and an experimental tool to present stimulus words were developed. Seventy-two elderly Chinese adults took part in the experiment. The findings indicate that, for a screen magnifier, the overlapping mode is superior to the parallel mode; the yellow-highlighted background is superior to the non-highlighted background; for lower-density text, the dual output mode (visual+auditory) is superior to the mono output mode (visual only), while for the higher-density text, no difference was found between the mono and dual output modes. Based on the findings, several recommendations are made. The overlapping mode should be set as the default working mode. Yellow could be a reasonable choice of background color for a magnifier when the text is black. Auditory output support should be used, and users should be advised to use dual output when the text density is lower and mono output when the text density is higher.