New obstacle avoidance for people with low vision

A new system, developed by researchers at the University of Washington helps people with low vision get around by representing obstacles as icons projected onto their retinas. It uses an infrared camera to track objects and a display that projects the 100 by 40 pixel icons through a vibrating fiber, all run by a laptop in a backpack. Currently the system is big and ugly (really it looks like the woman is going camping for a month) but the researchers plan to make it smaller and more affordable. We're just wondering how icons can adequately represent the myriad obstacles one would encounter in everyday life. It says different icons can be used for different obstacles but how exactly does one represent a barking dog held by an ornery old woman?