At the Rotterdam Zoo, visitors are given 'look at the ceiling' glasses.

After a gorilla broke out of its enclosure and attacked a woman at the Rotterdam Zoo, Holland, visitors were given glasses with eyes depicted on them, looking into the upper left corner. Glasses in the style of "look at the ceiling" are needed in order to avoid eye contact with primates, for which a direct look is a manifestation of aggression. And they see in these glasses through small holes located in the middle of the "lenses".